The review, authored by Asma Nouira of the University of Évora and University of Tunis El Manar and Imene Bekri-Abbes of the CNRSM Technopole of Borj Cédria, systematically analyzes how different carbon structures transform the properties of polyaniline, known to materials scientists as PANI. The numbers are striking. A composite of polyaniline anchored covalently inside a three-dimensional porous skeleton of reduced graphene oxide and helical carbon nanotubes achieved a specific capacitance of 696.75 farads per gram, compared with 274.75 farads per gram for pure PANI. More dramatically, the composite retained 93.57 percent of its capacitance over 3,500 charge-discharge cycles, while the pristine polymer managed only 72.3 percent retention after just 2,500 cycles.

The roots of the problem lie in polyaniline’s own chemistry. The rigid conjugated backbone that makes the polymer electrically conductive also renders it mechanically brittle, prone to cracking and delamination when strained. Its highly conductive emeraldine salt form is stable only below pH 4, which severely limits biomedical and environmental uses that operate near neutral conditions. During electrochemical cycling, the polymer swells and contracts with each doping and dedoping event, generating mechanical stress that destroys films over time. And because PANI chains aggregate into densely packed granules, many potentially useful electroactive sites are simply locked away from the electrolyte.

Carbon nanomaterials attack each of these weaknesses in a different way. One-dimensional carbon nanotubes act as electron highways, allowing charge to travel through the nanotube network rather than relying solely on the polymer backbone, while simultaneously reinforcing the composite like nanoscale rebar. Two-dimensional graphene offers exceptional conductivity and mechanical strength, though its pristine hydrophobic surface must usually be functionalized, most commonly through oxidation to graphene oxide and subsequent reduction, to disperse in water and bind with aniline monomers. Zero-dimensional carbon dots and graphene quantum dots introduce quantum confinement effects and, when covalently linked to aniline molecules before polymerization, serve as multifunctional crosslinking nodes that prevent chain aggregation.

The choice of synthesis route turns out to matter as much as the choice of carbon. In situ polymerization, in which aniline is polymerized directly in the presence of dispersed carbon nanomaterials, remains the most scalable and industrially viable method, though achieving uniform dispersion at large volumes is challenging. Electrochemical polymerization offers exquisite control over film thickness and doping level by driving aniline oxidation on a conductive substrate with cyclic voltammetry, but it is fundamentally limited to thin films on conducting electrodes. Microwave-assisted synthesis, which heats polar molecules directly through dielectric heating, can be extraordinarily fast: one recent study prepared CNT/Ag/PANI composite electrodes in just 50 seconds.

More exotic techniques push performance further. Cryo-polymerization carries out oxidative polymerization at temperatures between minus 20 and minus 78 degrees Celsius, using growing ice crystals as a sacrificial template to create lightweight, three-dimensional macroporous aerogels. Composites of polyaniline with carbon nanofibers made this way reached gravimetric capacitances of 201 farads per gram, three to six times higher than carbon-fiber-free counterparts. Gamma radiation-assisted fabrication, meanwhile, generates free radicals that initiate polymerization and crosslinking without any chemical oxidant, a clean route recently used to produce flexible energy-storage electrodes from sugarcane bagasse waste.

Perhaps the strongest message of the review is that covalent bonding between the polymer and its carbon scaffold yields qualitatively better materials than simple physical mixtures. Where the two phases are chemically linked, phase separation and delamination under mechanical load largely disappear. The synergy is visible across applications: a ternary composite of polyaniline, reduced graphene oxide and single-walled carbon nanotubes raised electrochromic optical contrast from 0.38 to 0.52 and cut switching times to as fast as 0.78 seconds, enabling smart windows and low-power displays that change color on demand.

The applications extend well beyond electronics. Nitrogen-rich polyaniline binds carbon dioxide through acid-base and dipole-quadrupole interactions, and when combined with hierarchically porous carbon aerogels containing ultramicropores of 0.54 to 0.64 nanometers, it achieved a CO2 capture capacity of 6.04 millimoles per gram. In microbial fuel cells, a polyaniline coating on a covalent organic framework-carbon nanotube cathode delivered power densities 8.65 times higher than a blank cathode, using bacteria to convert wastewater organic matter into electricity. Magnetic activated carbon composites functionalized with polyaniline removed lead ions from water at 348.39 milligrams per gram, while biomass-derived activated carbons from coconut husk and date seeds are turning agricultural waste into supercapacitor electrodes with retention above 98 percent after 50,000 cycles.

The review’s authors are candid about what still stands between the laboratory and the factory. Long-term operational stability under realistic conditions, with high current densities, neutral pH and repeated mechanical deformation, remains poorly characterized, and few studies subject materials to simultaneous electrochemical and mechanical fatigue. Only in situ polymerization is currently suitable for tonne-scale production; covalent conjugation, despite its superior interfacial quality, has been demonstrated only at milligram-to-gram scale and relies on hazardous solvents and coupling reagents. The authors also point to machine learning as an underexploited accelerator: with a design space spanning carbon type, dimensionality, loading, dopant acid and processing parameters, data-driven models trained on hundreds of composite systems could predict conductivity and sensing performance far faster than trial-and-error experimentation.

What emerges from the analysis is a portrait of a mature field at an inflection point. The fundamental science, linking the dimensionality and surface chemistry of carbon nanomaterials to the electrochemical, mechanical and optical behavior of the resulting composites, is now well established. Biomass-derived porous carbons, green oxidants and continuous-flow reactors are beginning to address the sustainability deficits of conventional synthesis. If scalable manufacturing and rigorous durability testing catch up with the materials themselves, polyaniline’s century-and-a-half-long journey from an obscure blue-black precipitate to the backbone of flexible supercapacitors, electrochromic windows and carbon-capturing aerogels may finally reach its commercial destination.

Subject of Research: Polyaniline-carbon nanocomposite synthesis, properties and emerging applications

Article Title: Design and functional performance of polyaniline-carbon nanocomposites: synthesis, properties, and emerging applications

Article References: Nouira, A., & Bekri-Abbes, I. (2026). Design and functional performance of polyaniline-carbon nanocomposites: synthesis, properties, and emerging applications. Frontiers in Carbon, 5, Article 1925654. https://doi.org/10.3389/frcrb.2026.1925654

Image Credits: AI Generated

DOI: 10.3389/frcrb.2026.1925654

Keywords: polyaniline, carbon nanomaterials, supercapacitors, graphene, carbon nanotubes, electrochromic devices, CO2 capture, energy storage, nanocomposites, conducting polymers, biomass-derived carbon, electrochemical stability

The team’s strategy centers on peracetic acid, an organic peroxide increasingly favored as a greener alternative to chlorine-based oxidants. When peracetic acid is activated on a catalyst surface, it can follow two competing reaction channels. One is nucleophilic in character and leads toward hydroxyl radicals, with all their attendant inefficiencies. The other is electrophilic and produces the acetylperoxyl radical, a species that carries a positive affinity for electron-rich structures such as the aromatic rings and electron-donating functional groups that decorate many pharmaceuticals, endocrine disruptors and industrial chemicals. Crucially, the acetylperoxyl radical persists far longer in aqueous solution than the hydroxyl radical, giving it a much larger diffusion radius and a far better chance of encountering the pollutant molecules it is designed to destroy. The difficulty has always been that conventional catalysts show little preference between the two pathways, so the desired electrophilic route remains a minority player.

The researchers’ solution was to redesign the electronic structure of the catalyst itself. Their starting material is biochar, a carbon-rich solid produced by heating biomass, in this case nitrogen-containing agricultural and forestry residues that would otherwise be treated as waste. Rather than relying on the intrinsic reactivity of pristine carbon, the team developed what they describe as a universal nitrogen-removal strategy to carve a specific class of topological defects into the carbon lattice: vacancy-pentagon arrangements known as 5-14-5 defects. These structures arise when nitrogen atoms are stripped from the carbon framework, leaving behind paired vacancies bounded by five-membered carbon rings. Such defects are not merely physical holes in the lattice; they fundamentally alter how electrons are distributed across the material, and the team set out to quantify exactly how.

Using a combination of spectroscopic characterization and computational modeling, the researchers showed that the 5-14-5 vacancy-pentagon defects perform two complementary electronic operations. First, they downshift the Fermi level of the carbon framework, which means the material’s highest occupied electronic states sit lower in energy and the surface becomes hungry for electrons. Second, they upshift the p-band center, raising the energy of the carbon p-orbitals that participate in bonding and electron transfer with adsorbed molecules. Together, these two shifts transform the biochar from its conventional role as an electron donor, the passive identity that carbon catalysts have typically held in peroxide activation, into a potent electrophilic sink that pulls electrons out of peracetic acid molecules adsorbed on its surface.

The magnitude of this transformation is captured in a single number: an electron accepting capacity of 3.77 millimoles of electrons per gram of catalyst, a figure the authors report as superior among comparable carbon materials. This electron-hungry character has a decisive thermodynamic consequence. Density functional theory calculations indicate that the electrophilic pathway, in which the defect sites abstract electrons from peracetic acid to generate the acetylperoxyl radical, becomes energetically favorable, with a calculated free energy change of minus 0.09 electron volts. In practical terms, the catalyst no longer merely permits the desired radical channel; it actively prefers it. Experimental probing of the radical species confirmed the outcome, showing that more than 99 percent of the radical flux is channeled into the acetylperoxyl route rather than the hydroxyl route, a degree of selectivity that approaches totality.

Selectivity alone would be a laboratory curiosity if it came at the cost of speed, but the engineered biochar delivers on kinetics as well. The team reports a normalized kinetic constant of 409.82 per minute per molar unit, a measure of how rapidly contaminants are degraded per unit of oxidant concentration. This high rate reflects the fact that every defect site acts as a dedicated reaction center that funnels oxidant molecules into the productive pathway, rather than squandering activation energy on side reactions. The system also proved remarkably durable. In continuous-flow operation, the catalyst sustained high-flux radical production for more than 260 hours, an endurance test that addresses one of the most persistent criticisms of defect-engineered carbons, namely that their exotic active sites degrade or deactivate under real operating conditions.

The environmental credentials of the technology were assessed through a life-cycle analysis, which the authors report validates the approach as sustainable and highlights a net-negative carbon footprint. This result follows from the raw materials and the chemistry alike. The biochar is derived from nitrogen-containing agro-forestry biomass, effectively locking carbon that plants drew from the atmosphere into a durable, useful solid rather than releasing it through burning or decomposition. Peracetic acid, meanwhile, degrades into acetic acid and water, leaving behind none of the chlorinated byproducts that plague conventional disinfection. The combination of a waste-derived catalyst, a benign oxidant and a selective reaction pathway means that less chemical input is needed per unit of pollutant destroyed, which cascades through the entire life cycle in the form of lower manufacturing, transport and dosing burdens.

The conceptual advance here extends beyond any single contaminant or catalyst formulation. For decades, radical chemistry in environmental engineering has been treated as an unmanageable brute force, something to be generated in quantity and tolerated in its promiscuity. The new work demonstrates that the direction of radical chemistry can be dictated at the level of atomic topology, by designing defects that reshape the electronic landscape of a catalyst with the same deliberateness that semiconductor engineers design band structures in silicon. The nitrogen-removal strategy that creates the 5-14-5 defects is described as universal, suggesting it could be applied across a range of nitrogen-containing biomass feedstocks rather than depending on one particular precursor, which is essential for any technology hoping to scale from the bench to municipal treatment plants.

There are, of course, familiar gaps between a landmark paper and a working treatment train. The study’s performance figures were obtained under controlled conditions, and real wastewaters present matrices whose complexity can challenge even selective oxidants. The long-term stability of defect populations under years of service, the cost of producing biochar with precisely controlled defect densities at industrial scale, and the regeneration or disposal of spent catalyst all remain questions for future engineering. Yet the 260-hour continuous operation result and the life-cycle assessment together suggest that these are questions of optimization rather than fundamental obstacles. The authors frame their contribution as providing fundamental insights into defect-mediated radical chemistry alongside a scalable, sustainable paradigm for precision water decontamination, and the evidence they present supports both halves of that claim.

What makes the work resonate beyond environmental chemistry is its demonstration that selectivity, the most elusive virtue in oxidation chemistry, can be engineered rather than sacrificed. A pollutant molecule in a complex wastewater stream is now, in principle, the most electron-rich target in the room, and a catalyst that behaves as an electrophilic sink will find it preferentially. As regulators tighten limits on pharmaceuticals, per- and polyfluoroalkyl substances and other trace contaminants that conventional plants were never designed to remove, technologies that destroy specific molecular motifs with minimal collateral chemistry will move from desirable to necessary. This defect-engineered biochar, grown from agricultural waste and tuned one vacancy at a time, offers a compelling glimpse of what that next generation of water purification may look like.

Subject of Research: Defect-engineered electrophilic biochar for selective radical-mediated water purification

Article Title: Selective radical pathways on defect-engineered electrophilic biochar for sustainable water purification

Article References: Hu, Y., Ren, W., Wang, M., Xu, Z., & Zhu, Y. (2026). Selective radical pathways on defect-engineered electrophilic biochar for sustainable water purification. Nature Communications. https://doi.org/10.1038/s41467-026-78421-z

Image Credits: AI Generated

DOI: 10.1038/s41467-026-78421-z

Keywords: biochar, advanced oxidation processes, peracetic acid, acetylperoxyl radical, hydroxyl radical, topological defects, vacancy-pentagon defects, electrophilic catalysis, water purification, life-cycle assessment, biomass-derived carbon, environmental chemistry

The central challenge the team set out to address is one that has long frustrated designers of biomass-derived carbons. Porous carbons made from plant and algal precursors are attractive because they are cheap, renewable, and naturally rich in the light elements that make carbon such a versatile electrode scaffold. Yet producing a material that simultaneously offers a large accessible surface area, an interconnected network of pores spanning multiple length scales, and effective incorporation of nitrogen heteroatoms has proved elusive. Too often, aggressive activation opens up enormous surface area but destroys the conductive pathways that ions and electrons need, or it generates a chaotic pore landscape in which much of the surface is buried behind bottlenecks that electrolyte ions cannot reach in the microseconds that separate charge and discharge in a high-power device.

The Visakhapatnam group’s solution lies in a dual-function additive that does two jobs at once. Ammonium chloride, a cheap and benign crystalline salt, was blended with the agar precursor before heat treatment. During carbonization, the salt decomposes to release gaseous species that blow through the softening carbon matrix like tiny jets of air through molten glass, carving out an open, graphene-like framework studded with pores. At the same time, the decomposition chemistry supplies nitrogen atoms that substitute into the carbon lattice itself. This in situ approach means that pore formation and nitrogen doping happen in a single, scalable step rather than requiring separate post-treatment stages, an important consideration for any process that might one day leave the laboratory. The nitrogen atoms, particularly in their pyridinic and graphitic configurations, are known to improve the electronic conductivity of the carbon and to contribute additional pseudocapacitance through faradaic interactions with the electrolyte.

After the ammonium chloride-assisted carbonization, the team applied a second, equally critical step: activation with potassium hydroxide. Chemical activation with KOH is the workhorse of the porous carbon field, etching the carbon skeleton and generating the micropores and small mesopores that give supercapacitor electrodes their enormous internal surface area. But the ratio of KOH to carbon, and the temperature at which the activation is carried out, must be tuned with precision. Too little activator, and the surface area remains modest; too much, and the carbon structure collapses into a poorly connected, low-conductivity sponge. The researchers systematically varied both the carbonization and activation temperature and the KOH-to-carbon weight ratio, ultimately arriving at a graphene-like hierarchical architecture in which macropores feed mesopores, which in turn feed the dense mesh of micropores where most of the charge is stored.

This hierarchy is not merely an aesthetic achievement; it is the kinetic heart of the device. Recent work in the field has emphasized that the tortuosity of the pore network, the winding-ness of the paths that ions must follow, can be the dominant factor controlling how fast a supercapacitor can charge. A material with a huge surface area but a tortuous, poorly connected pore system will store plenty of charge if given time but will choke at high current. The interconnected pathways engineered into the agar-derived aerogel allow sulfate and sodium ions to penetrate deep into the electrode rapidly, so that a large fraction of the theoretical surface remains accessible even at demanding rates. That is precisely what the measured power density of 23.18 kilowatts per kilogram reflects: the ability to deliver stored energy quickly, without the voltage losses that plague more convoluted structures.

The choice of electrolyte deserves its own attention. Aqueous electrolytes are the safety and sustainability darlings of the energy storage world; they are non-flammable, inexpensive, and easy to handle compared with the organic solvents used in most commercial devices. Their historical weakness has been the narrow voltage window imposed by the electrolysis of water, which limits energy density because stored energy scales with the square of the voltage. Operating a symmetric carbon-carbon device at 1.3 volts in a neutral 1.5 molar sodium sulfate solution is a meaningful achievement, and it reflects both the stability of the optimized carbon surface and the buffering behavior that neutral salt electrolytes can provide at the electrode interfaces. Every additional tenth of a volt in such a device translates into a disproportionate gain in usable energy.

Durability, the quality that separates laboratory curiosities from deployable technology, is where the new aerogel truly distinguishes itself. The symmetric supercapacitor retained approximately 87 percent of its initial capacitance after 50,000 complete charge-discharge cycles, with coulombic efficiency hovering near 100 percent throughout. Fifty thousand cycles is a punishing test; a lithium-ion battery subjected to equivalent treatment would typically have degraded far more severely. The structural integrity of the hierarchical carbon framework, with its robust graphene-like walls and absence of the dissolution or volume-change problems that afflict many battery electrode chemistries, underpins this endurance. To demonstrate practical relevance, the team showed that the device could power a light-emitting diode, a small but symbolic gesture toward real-world applications such as backup power, portable electronics, and buffers for intermittent renewable generation.

What elevates the study beyond a conventional materials report is its pairing of experiment with two complementary layers of analysis. First, the researchers carried out a kinetic deconvolution of the charge-storage mechanism, separating the contributions of fast, surface-localized capacitive processes from slower, diffusion-controlled ones. This kind of analysis reveals how much of the stored charge is available at high rates and how much depends on ions slowly infiltrating the narrowest pores, providing a quantitative map of where the design succeeds and where further gains might lie. Second, the team employed COMSOL Multiphysics simulations to visualize quantities that are nearly impossible to measure directly: the spatial distribution of current density within the porous electrode, the evolution of the local potential during charging and discharging, and the ion-concentration gradients that build up at the electrode-electrolyte interface. Such modeling, increasingly common in electroanalytical research, turns the black box of a porous electrode into a legible physical system.

The broader significance of the work lies in its demonstration of a complete biomass-to-device pipeline that is sustainable at every stage. The precursor is a renewable seaweed extract; the pore-forming and doping agent is a common, low-toxicity salt; the activation chemistry is standard and scalable; the electrolyte is water with an inexpensive sulfate salt; and the resulting device survives half a century’s worth of daily cycling in laboratory terms. As global demand for grid buffering, regenerative braking, and fast-response energy storage grows, the field of electrochemical capacitors has been searching for electrode materials that combine the power of carbon with energy densities that approach battery territory. This study suggests that the answer may not require exotic precursors or elaborate synthesis at all, but rather a deeper understanding of how to sculpt the invisible architecture of pores inside materials that nature has already provided, and how to read that architecture through the combined lens of electrochemical kinetics and multiphysics simulation.

Subject of Research: Nitrogen-doped porous carbon aerogels derived from agar for aqueous symmetric supercapacitors

Article Title: Pore engineering of agar-derived N-doped carbon aerogels for aqueous symmetric supercapacitors

Article References: Kumari, K., Das, G. S., & Ghosh, S. (2026). Pore engineering of agar-derived N-doped carbon aerogels for aqueous symmetric supercapacitors. Ionics. https://doi.org/10.1007/s11581-026-07564-2

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07564-2

Keywords: supercapacitors, carbon aerogel, agar-agar, biomass-derived carbon, nitrogen doping, KOH activation, hierarchical porosity, aqueous electrolyte, energy storage, COMSOL simulation, sodium sulfate, cycling stability

The starting point of the work is deceptively simple. Clam shells, composed largely of calcium carbonate, are converted through controlled thermal and chemical treatment into a honeycomb-structured porous activated carbon, which the researchers abbreviate CAC. This architecture is exactly what materials scientists prize in an electrode or catalyst support: an interconnected network of pores at multiple length scales that offers enormous internal surface area for ions to access, along with a conductive carbon scaffold that can anchor catalytically active particles. By sourcing the carbon from biowaste rather than fossil-derived precursors, the team also sidesteps one of the persistent criticisms of advanced energy materials, namely that their manufacture can carry a heavy environmental footprint of its own.

Onto this biological carbon scaffold the researchers deposited sphere-like particles of a cerium-doped lanthanum cobaltite, a perovskite oxide of the general formula LaCoO3 in which a small fraction of the lanthanum sites is occupied by cerium atoms. Perovskite oxides of this ABO3 family have attracted intense interest in recent years because their compositions can be tuned almost endlessly, allowing chemists to adjust their electronic structure, optical absorption and surface chemistry. Doping is the classic lever: substituting foreign cations into the crystal lattice distorts the structure, creates defects such as oxygen vacancies, and can dramatically improve charge transport and light harvesting. In this case, the cerium substitution modifies the cobaltite’s semiconductor characteristics in ways that make it a more effective visible-light photocatalyst and a more capable charge-storage material.

The synthesis itself was deliberately kept low-tech. The composite, designated CAC/LC:Ce, was prepared by a facile hydrothermal method, in which the precursor solution and the carbon support are heated together in a sealed vessel, allowing the perovskite spheres to nucleate and grow directly on the carbon surface. Hydrothermal processing is widely favored in green chemistry because it operates at modest temperatures, uses water as the reaction medium and avoids many of the toxic solvents and elaborate vacuum steps associated with other nanomaterial fabrication routes. The result is a one-pot marriage of biowaste-derived carbon and engineered oxide that could, in principle, be scaled without exotic equipment.

Characterization was correspondingly thorough. The team probed the crystal structure of all three materials with X-ray diffraction, examined their morphology with field-emission scanning electron microscopy and high-resolution transmission electron microscopy, and confirmed chemical composition and surface states using Fourier-transform infrared spectroscopy, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray analysis and Brunauer-Emmett-Teller surface area measurements. Two electrochemical techniques added crucial mechanistic depth. Mott-Schottky analysis revealed the semiconductor type and band structure of the cerium-doped cobaltite and the composite, mapping out the energy levels that govern how photogenerated electrons and holes separate, while transient photocurrent measurements under intermittent illumination demonstrated how efficiently the materials shuttle light-excited charges before they recombine and waste the absorbed energy.

The environmental half of the story centers on bromophenol blue, a widely used phenolic dye that serves as a stand-in for the colored organic pollutants that textile and dyeing industries discharge into waterways. Under visible-light illumination, the three materials showed a clear performance hierarchy in dye removal percentage. The clam shell carbon alone discolored 75 percent of the dye, the cerium-doped cobaltite managed 86 percent, and the combined composite reached 98 percent. That near-complete removal reflects a synergy between the two components: the porous carbon adsorbs dye molecules onto its extensive surface, concentrating them near the perovskite particles, which then generate reactive oxygen species under light that chemically dismantle the adsorbed pollutants. Scavenger experiments, in which specific radical quenchers are added to identify which reactive species dominate, allowed the team to pin down the key actors in the degradation chemistry.

Just as important as the headline efficiency is durability. Many photocatalysts lose activity after a few cycles as active sites are blocked by intermediates or the material itself degrades. The CAC/LC:Ce composite retained a 95 percent dye removal value on its fourth consecutive run, a strong indication that the anchoring of the perovskite on the robust carbon framework protects the active phase. The researchers also used liquid chromatography-mass spectrometry to trace the intermediate species formed as the dye broke down, reconstructing a plausible degradation pathway rather than simply reporting that the color disappeared. That distinction matters, because a decolorized solution can still contain toxic fragments, and a responsible remediation technology must demonstrate that the end products are genuinely benign.

To address that concern directly, the team evaluated the treated water biologically. Phytotoxicity tests using fenugreek, Trigonella foenum-graecum, assessed whether the degraded dye solution would still harm seed germination and plant growth, while ecotoxicity screening in zebrafish probed effects on aquatic organisms. These assays are a relatively rare but welcome step in photocatalysis research, where many studies stop at the discoloration percentage. By checking that the remediated water is compatible with both plant and aquatic life, the authors provide evidence for the practical reuse potential of the treated effluent, which is the ultimate test of any water-treatment technology intended for real-world deployment.

The energy-storage half of the study is equally striking. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy were used to evaluate electrodes fabricated from each material. The specific capacitances came out at 240 farads per gram for the clam shell carbon, 381 farads per gram for the cerium-doped cobaltite, and 652 farads per gram for the composite, a value that places the hybrid among the more capable perovskite-carbon electrodes reported in the supercapacitor literature. The composite electrode also held on to 91 percent of its initial capacitance after 3000 charge-discharge cycles, showing that the faradaic reactions at the perovskite surface do not rapidly degrade the electrode. To test performance at the device level, the team assembled a two-electrode asymmetric supercapacitor cell using the plain clam shell carbon as the negative electrode and the composite as the positive electrode, a configuration that widens the operating voltage window and is the standard route toward practical energy and power densities.

Taken together, the study offers a template for what sustainable materials chemistry can look like when the circular economy is designed in from the first step rather than bolted on at the end. A waste stream from the seafood industry becomes a porous carbon; that carbon hosts a doped perovskite engineered for visible-light activity; the resulting composite simultaneously tackles dye pollution and grid-relevant energy storage; and the safety of the cleaned water is verified with living organisms rather than assumed. Challenges certainly remain before such materials leave the laboratory, including scaling hydrothermal synthesis, validating performance with real textile effluents rather than model dyes, and demonstrating device-level cycling over far more than 3000 cycles. But the underlying message is compelling: with thoughtful design, the same humble material can help solve two of the defining problems of the coming decades, dirty water and the need for affordable energy storage, using nothing more exotic than clam shells, cerium and sunlight.

Subject of Research: A clam shell-derived activated carbon supporting cerium-doped lanthanum cobaltite perovskite for photocatalytic dye degradation and supercapacitor energy storage

Article Title: Sustainable synthesis of La–Ce mixed cobaltite anchored on clam shell-derived porous activated carbon for electrochemical energy storage and environmental remediation

Article References: Jose, V., Jose, V., Kuruvilla, E., & Nesaraj, A. S. (2026). Sustainable synthesis of La–Ce mixed cobaltite anchored on clam shell-derived porous activated carbon for electrochemical energy storage and environmental remediation. Ionics. https://doi.org/10.1007/s11581-026-07489-w

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07489-w

Keywords: clam shell activated carbon, perovskite, LaCoO3, cerium doping, photocatalysis, dye degradation, supercapacitor, asymmetric cell, biomass-derived carbon, water remediation, hydrothermal synthesis, specific capacitance

To understand why this matters, it helps to recall how a dye-sensitized solar cell actually works. In these devices, light is absorbed by dye molecules attached to a nanostructured titanium dioxide photoanode. Excited electrons are injected into the titanium dioxide and travel through an external circuit to the counter electrode. Meanwhile, the oxidized dye is regenerated by an electrolyte, usually containing the iodide-triiodide redox couple, which itself must be regenerated at the counter electrode. The counter electrode therefore has to catalyze the reduction of triiodide back to iodide efficiently; if it does not, the whole cycle stalls and the cell’s fill factor and efficiency suffer. Platinum has been the benchmark catalyst for this reaction because of its exceptional activity and stability, but it is scarce, expensive and increasingly unattractive for mass-market deployment.

The search for platinum alternatives has become one of the most active corners of dye-sensitized solar cell research. Over the past decade, researchers have explored transition metal sulfides, selenides, nitrides, carbides and oxides as catalytic counter electrode materials, often pairing them with conductive carbon scaffolds such as graphene, carbon nanotubes or activated carbon. The logic is straightforward: the catalyst provides the electrochemical activity, while the carbon provides the electrical conductivity and surface area needed to shuttle electrons and expose active sites to the electrolyte. Ferrites—mixed metal oxides with the general formula MFe2O4—have emerged as promising candidates because they combine reasonable electrocatalytic activity with chemical stability and low cost.

The new study, led by D. Sengeni of C.K. College of Engineering and Technology in Cuddalore, Tamil Nadu, with colleagues from several Chennai institutions, takes this approach a step further by sourcing the carbon scaffold from renewable agro-food waste rather than from commercially produced activated carbon. The team converted Bean Curd Stick waste into porous biocarbon and then combined it with nickel ferrite, NiFe2O4, a spinel oxide in which nickel and iron ions occupy the crystal lattice in a way that supports electrocatalytic activity. The novel aspect of the study, according to the authors, is precisely this utilization of renewable agro-food waste as a conductive carbon matrix to fabricate a high-performance ferrite-carbon hybrid electrode.

Structural and compositional analyses confirmed the successful formation of the NFO@BC composite, while microscopic studies revealed the uniform anchoring of NiFe2O4 nanoparticles on the porous biocarbon surface. That uniformity is not merely cosmetic. In hybrid counter electrodes, the distribution of catalyst particles across the conductive scaffold determines how effectively electrons can reach active sites. If the ferrite particles cluster together, large portions of the carbon surface remain catalytically inert and the electrolyte cannot access much of the catalyst. Uniform anchoring, by contrast, means that nearly every ferrite nanoparticle is electrically connected to the carbon network and simultaneously exposed to the iodide-triiodide electrolyte, maximizing the density of accessible electrocatalytic sites.

One of the most striking quantitative results from the study comes from Brunauer-Emmett-Teller, or BET, surface area analysis, which revealed a specific surface area of 286.7 square meters per gram for the NFO@BC composite. For an electrode material, that is a substantial figure, and it has direct electrochemical consequences. A high surface area provides abundant accessible electrocatalytic sites and improved contact with the electrolyte, allowing the triiodide reduction reaction to proceed rapidly at the electrode-electrolyte interface. Porosity also matters for ion transport: the pores within the biocarbon matrix create pathways through which the electrolyte can penetrate the electrode, shortening diffusion distances and reducing the charge-transfer resistance that would otherwise limit current output.

The authors attribute the enhanced photovoltaic performance of their cells to the synergistic effect of the conductive biocarbon and the electrocatalytically active NiFe2O4. This division of labor is the central design principle of the hybrid. The biocarbon, derived from biomass, acts as a three-dimensional conductive network that collects electrons arriving from the external circuit and distributes them across the electrode. The nickel ferrite nanoparticles, dispersed across that network, serve as the catalytic workhorses where the triiodide ions are actually reduced. Neither component alone would perform as well: bare biocarbon lacks the catalytic activity of the ferrite, while bare nickel ferrite suffers from the modest electrical conductivity typical of spinel oxides. Together, they address each other’s weaknesses.

The broader context of this work is the push to commercialize dye-sensitized solar cells, which the authors identify as the motivation for developing inexpensive, effective and sustainable platinum-free counter electrodes. Dye-sensitized cells are attractive for applications where conventional panels struggle—indoor lighting, building-integrated photovoltaics, and devices that benefit from semi-transparency and flexibility. But every cost component counts. Platinum loading on a counter electrode may seem like a small fraction of a cell’s material budget, yet at the scale of gigawatt production the price of platinum becomes prohibitive, and its supply chain carries significant environmental and geopolitical burdens. Replacing it with a material synthesized from food waste and abundant iron and nickel compounds changes that calculus fundamentally.

The choice of Bean Curd Stick waste also fits into a growing body of research on biomass-derived carbons for energy devices. Biomass precursors are attractive because they are renewable, widely available and often rich in the heteroatoms that can enhance the catalytic properties of the resulting carbon. Previous work by some of the same research community has examined heteroatom doping in Bean Curd Stick-derived porous carbon for platinum-free counter electrodes, and other groups have used bamboo-derived activated carbon in similar ferrite composites. The present study extends this line of inquiry by demonstrating that the biocarbon matrix can host nickel ferrite nanoparticles uniformly, creating a composite whose texture and chemistry are both favorable for triiodide reduction.

The implications reach beyond a single laboratory result. If hybrid electrodes of this kind can be produced reliably from waste streams, dye-sensitized solar cells could move closer to the cost profile that made them famous after their invention by Brian O’Regan and Michael Grätzel in 1991. The study also illustrates a broader trend in materials science: the convergence of waste valorization and clean energy technology, where one environmental problem—food waste—is enlisted to solve another, the cost and scarcity of critical materials in renewable energy hardware. The authors conclude that NFO@BC stands out as a low-cost, sustainable and efficient platinum-free counter electrode for dye-sensitized solar cell applications, and their results suggest that the humble tofu stick, of all things, may have a role to play in the solar panels of the future.

Subject of Research: Pt-free dye-sensitized solar cell counter electrodes based on NiFe2O4 and biomass-derived biocarbon

Article Title: Development of NiFe2O4@Biocarbon hybrid counter electrode for efficient Pt-free dye-sensitized solar cells

Article References: Sengeni, D., Vinayagam, P., Karuppiah, S., Velmurugan, V., Bindhu, M., & Sevvanthi, S. (2026). Development of NiFe2O4@Biocarbon hybrid counter electrode for efficient Pt-free dye-sensitized solar cells. Ionics. https://doi.org/10.1007/s11581-026-07557-1

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07557-1

Keywords: dye-sensitized solar cells, counter electrode, NiFe2O4, biocarbon, platinum-free, Bean Curd Stick waste, nickel ferrite, biomass-derived carbon, triiodide reduction, photovoltaics, BET surface area, agro-food waste

The star of the study is rhenium disulfide, or ReS2, a member of the transition metal dichalcogenide family that also includes the better-known molybdenum disulfide. What makes ReS2 special among two-dimensional materials is its unusually weak interlayer coupling: unlike MoS2, whose stacked layers interact strongly, the individual ReS2 sheets behave almost as if they were isolated, giving the material effectively two-dimensional electronic and optical properties even in thick crystals. For electrochemists, that decoupled structure is a gift. It means ions and electrons can access active sites throughout the material rather than only at the surfaces, and ReS2 has already earned a reputation as a high-rate pseudocapacitive energy storage material in earlier work. Pseudocapacitance, unlike the purely electrostatic charge storage of carbon double-layer capacitors, involves fast, reversible faradaic reactions at or near the electrode surface, allowing much higher charge storage per unit mass.

But ReS2 has two Achilles heels. First, like many layered sulfides, it suffers from structural deterioration during repeated cycling: as ions push in and out of the lattice, the material swells, cracks and eventually detaches from the current collector, killing the electrode. Second, its intrinsic electrical conductivity is poor, which throttles the very fast charge transport that pseudocapacitors need. The Lingnan Normal team set out to solve both problems at once with a single architectural move: anchoring ReS2 nanoparticles onto conductive, nitrogen-doped carbon nanosheets made by pyrolyzing folic acid. The carbon scaffold acts as a mechanical buffer that suppresses the aggregation of ReS2 particles and absorbs the mechanical strain of cycling, while the interconnected carbon network provides a highway for rapid electron transport and ion diffusion throughout the electrode.

The choice of folic acid as the carbon and nitrogen precursor is more than a laboratory curiosity. The vitamin molecule is rich in nitrogen atoms, carrying pteridine, amide and amine groups within a single compact structure, so when it is heated in the absence of oxygen it self-assembles into ultrathin carbon sheets with nitrogen already woven into the lattice. That built-in nitrogen doping matters electrochemically: nitrogen atoms in the carbon framework alter the local electronic structure, improve wettability with aqueous electrolytes and can contribute additional pseudocapacitance of their own. Previous studies have shown that folic acid pyrolysis yields nitrogen-doped graphitic carbon with well-defined structural evolution, and the approach has been used to host single-atom metal catalysts. Here, the researchers harnessed the same chemistry to create a conductive, nitrogen-rich mat on which ReS2 nanoparticles could be grown and anchored through a facile pyrolysis route.

The fabrication strategy follows a broader and rapidly growing trend in electrode engineering: hybridizing metal sulfides with biomass-derived or molecule-derived nitrogen-doped carbon. In recent years, teams have embedded tungsten disulfide in gelatin-derived honeycomb carbon networks, coupled tin sulfide with nitrogen-doped porous carbon, nanoconfined ReS2 in biomass-derived three-dimensional porous carbon architectures, and grown manganese sulfide on carbon sheets from coordination frameworks. The logic is always the same. The sulfide supplies high theoretical capacitance; the carbon supplies conductivity, structural confinement and extra surface area; and the nitrogen dopants boost both the electronic properties of the carbon and its chemical affinity for the sulfide phase. What distinguishes the new work is the molecular precision of the folic acid precursor, which delivers a high nitrogen content without the need for separate nitrogen sources or harsh post-treatments.

The electrochemical results are striking. The ReS2/nitrogen-doped carbon electrode delivered a specific capacitance of 758.78 farads per gram at 1 ampere per gram, a figure that places it among the better-performing transition metal dichalcogenide-carbon hybrids reported for pseudocapacitors. Equally important was the material’s superior rate capability, meaning it retained a large fraction of its capacitance as the charging current was increased. Rate capability is where many high-capacitance materials fail, because sluggish ion diffusion and poor conductivity cannot keep up with fast charge injection. The interconnected carbon network in the composite appears to have solved that bottleneck, allowing electrons to reach the ReS2 particles and ions to reach the active sites even at high current densities.

To test the material under realistic device conditions, the researchers constructed an asymmetric supercapacitor, pairing the ReS2/carbon composite as one electrode with a counter-electrode of complementary potential range. Asymmetric designs are the standard route to high-voltage aqueous supercapacitors: by using two electrodes with different operating windows, the total cell voltage, and with it the energy density, can be pushed well beyond what either electrode could achieve alone, since stored energy scales with the square of voltage. The resulting device achieved an energy density of 15.32 watt-hours per kilogram alongside a power density of 3.16 kilowatts per kilogram. For context, that energy density approaches the lower range of lead-acid batteries while retaining the rapid charge-discharge behavior and power delivery characteristic of supercapacitors, a combination that makes such devices attractive for regenerative braking, grid frequency regulation and portable electronics.

The work also speaks to a wider question in materials chemistry: how to design electrodes that survive the mechanical punishment of cycling. The nanosheet architecture of the composite is central here. Because the ReS2 nanoparticles are well anchored and spatially separated on the carbon sheets, they cannot coalesce into larger particles during cycling, and the flexible carbon matrix absorbs the volume changes that would otherwise fracture a bulk electrode. This confinement-and-buffering principle has proven its worth across the sulfide-carbon literature, from lithium and sodium battery anodes to supercapacitor electrodes, and the new study extends it to one of the least conventional dichalcogenides. The authors note that the composite demonstrates clear potential as an electrode for energy conversion and storage devices, positioning ReS2 hybrids alongside more established candidates.

Challenges remain before vitamin-derived rhenium electrodes power anything in your pocket. Rhenium is one of the rarest and most expensive elements on Earth, which likely confines ReS2 devices to niche, high-value applications unless loading can be minimized or the material recycled. The study reported here is an early-stage laboratory demonstration, and long-term cycling data, manufacturing scalability and full cost analysis will determine whether the architecture can make the leap from beaker to product. Still, the research adds an elegant entry to the catalog of molecule-derived carbon scaffolds, showing that a humble vitamin can be transformed into the conductive backbone of a high-performance energy storage material. As the demand for fast-charging, long-lived energy storage continues to grow, hybrid electrodes that marry reactive sulfides with nitrogen-doped carbon, whether derived from vitamins, biomass or metal-organic frameworks, are likely to remain at the forefront of the field, and this folic acid route offers a particularly clean and versatile way to build them.

Subject of Research: ReS2/nitrogen-doped carbon nanocomposites for pseudocapacitive supercapacitor electrodes

Article Title: ReS2 hybridized with folic acid-derived N-incorporated carbon sheets to enhance pseudocapacitive property

Article References: Wang, J., Yuan, Y., Liang, Q., Wang, X., Ma, L., Jiang, R., Cai, H., & Xi, Y. (2026). ReS2 hybridized with folic acid-derived N-incorporated carbon sheets to enhance pseudocapacitive property. Ionics. https://doi.org/10.1007/s11581-026-07560-6

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07560-6

Keywords: supercapacitors, rhenium disulfide, nitrogen-doped carbon, folic acid, pseudocapacitance, nanocomposites, transition metal dichalcogenides, energy storage, pyrolysis, asymmetric supercapacitor, electrode materials, biomass-derived carbon

Supercapacitors occupy a unique niche in the energy storage landscape. Unlike batteries, which store charge in slow chemical reactions, electrochemical double-layer capacitors, or EDLCs, store energy physically, as ions from the electrolyte accumulate on the surface of porous carbon electrodes. That mechanism delivers exceptional power density, near-instant charge and discharge, long cycle life, and outstanding efficiency. The trade-off has always been energy density, which depends critically on how much electrolyte-accessible surface the electrode offers. Activated carbon remains the workhorse material for these devices, typically delivering specific capacitances between 100 and 500 farads per gram, and its appeal is amplified by the fact that it can be made from cheap, renewable agricultural waste such as corncob, rice husk, coconut shell, and orange peels.

The catch lies in the activation step. Conventional physical activation involves heating a carbon precursor above 700 degrees Celsius in steam or carbon dioxide, which selectively gasifies carbon atoms to open and widen pores. Chemical activation with agents such as potassium hydroxide, sodium hydroxide, or phosphoric acid generally achieves higher surface areas and more uniform pore distributions, but it still demands temperatures around 800 degrees Celsius, long processing times, and substantial energy input. Both routes carry environmental and economic penalties, and both offer limited control over the final pore architecture. Any method that can achieve comparable porosity at lower temperature, in less time, and with less energy would represent a meaningful advance for sustainable electrode manufacturing.

Microwave irradiation offers exactly that possibility, and the new study exploits it elegantly. Unlike conventional furnaces that heat from the outside in through conduction, microwaves couple directly with the carbon matrix through dielectric and conductive losses, producing rapid, volumetric, and selective heating. Localized hot spots form at conductive or defect-rich regions, and in this case at the interfaces between the carbon and the potassium hydroxide activator, which itself acts as a porogen and a microwave absorption medium. The result is accelerated etching, faster diffusion of the activating agent into the carbon interior, and the formation of well-defined micro- and mesoporous networks in minutes rather than hours, all while avoiding the structural collapse that prolonged conventional heating can cause.

The raw material itself is unconventional. The team, led by Poonam Mahendia and Ritu Jangra with senior author Suman Mahendia of Kurukshetra University, burned a 250-milligram cotton wick in an earthen cup lamp filled with sesame oil, covering it with a stainless steel vessel to trap the smoke. Sesame oil is rich in polyunsaturated fatty acids, containing roughly 40 to 50 percent linoleic acid and 33 to 44 percent oleic acid. During combustion, these long-chain triglycerides decompose through cracking, dehydrogenation, aromatization, and incomplete oxidation, generating soot-like carbon particles. The oil thus serves three roles at once: it supplies the carbon skeleton, its unsaturated fatty acids promote partial aromatization into defective, turbostratic carbon domains that are far more reactive toward potassium hydroxide etching than graphitized carbon, and the incomplete combustion leaves behind oxygen-containing surface groups that improve wettability in aqueous electrolytes and may contribute additional charge storage.

The synthesis route was deliberately simple. The black powder peeled from the vessel walls was first carbonized at 400 degrees Celsius for two and a half hours under nitrogen to yield what the researchers call bare carbon, with a modest surface area of 92.5 square meters per gram and a total pore volume of 0.13 cubic centimeters per gram. That material was then mixed with potassium hydroxide in a five-to-one ratio in deionized water, stirred for 24 hours, dried into a thick paste, and subjected to microwave heating at 110 degrees Celsius in convection mode at full 1200-watt power for just five minutes. Washing with dilute hydrochloric acid and water removed residual impurities, leaving the activated carbon, designated AA, with a surface area of 686 square meters per gram and a pore volume of 0.44 cubic centimeters per gram.

Characterization confirmed the transformation at every scale. Nitrogen adsorption isotherms showed that activation shifted the material toward a type IV profile with a larger hysteresis loop, indicating a higher proportion of mesopores, the ion-transport channels that complement the micropores responsible for double-layer formation and capacitance. X-ray diffraction revealed broad, low-intensity peaks near 23 and 43 degrees, signatures of highly disordered carbon, with the activated sample showing an expanded interlayer spacing of 0.39 nanometers compared with 0.37 nanometers before activation, both well above graphite’s 0.335 nanometers. That disorder, the authors note, reflects carbon layers separated by functional groups and structural defects, which create additional active sites for charge storage. Scanning electron microscopy completed the picture, showing layer-like carbon sheets with sparse porosity before activation and a well-developed pore structure throughout the sample afterward.

The electrochemical results are where the five-minute treatment truly pays off. Cyclic voltammetry produced nearly rectangular curves characteristic of ideal double-layer behavior, with specific capacitances of 300 farads per gram for the activated material against just 18 farads per gram for the untreated carbon at 10 millivolts per second. Galvanostatic charge-discharge testing at 1 ampere per gram delivered the headline figure of 485 farads per gram, along with an energy density of 33.68 watt-hours per kilogram at a power density of 628.23 watts per kilogram in 6 molar potassium hydroxide electrolyte. Impedance spectroscopy showed a low charge-transfer resistance of 0.3 ohms, far below the 2.06 ohms of the untreated device, indicating fast charge transport and excellent electrode-electrolyte contact. Cycling stability proved equally convincing: after 5000 charge-discharge cycles at a demanding 20 amperes per gram, the device retained 84 percent of its capacitance with 100 percent coulombic efficiency.

To demonstrate practical viability, the researchers connected three identical devices in series, since aqueous electrolytes limit single cells to roughly one volt before water begins to dissociate. The stack operated stably across the 1-to-2-volt and 2-to-3-volt windows and powered a red light-emitting diode for about 65 seconds, a small but tangible proof that lamp soot from a kitchen microwave can do real electrical work. The series combination did show an increased internal resistance of 10.22 ohms, a reminder that device integration still poses engineering challenges, but the overall performance compares favorably with literature values for microwave-activated carbons, including silkworm-excrement-derived carbon at 322 farads per gram, paper-waste carbon at 237 farads per gram, and food-waste aerogels at 316 farads per gram with 16.3 watt-hours per kilogram.

What makes this work resonate beyond its numbers is the radical accessibility of the process. The precursor costs pennies, the activation step runs at 110 degrees Celsius instead of 800, and the total microwave exposure is measured in minutes, translating directly into energy and time savings over conventional thermochemical routes. As the demand for grid buffers, regenerative braking systems, and portable electronics grows, so does the incentive to find electrode materials that are cheap, abundant, and environmentally benign. Turning the soot of a sesame-oil lamp into a 485-farad-per-gram electrode suggests that the path to sustainable energy storage may sometimes run through the most humble corners of the household, one five-minute microwave pulse at a time.

Subject of Research: Microwave-assisted synthesis of activated carbon from cotton and sesame oil combustion soot for supercapacitor electrodes

Article Title: Microwave-assisted synthesis of activated carbon from aerobic combustion of cotton in sesamee oil for high performance supercapacitor

Article References: Mahendia, P., Jangra, R., Karakoti, M., Sinha, O. P., Sahoo, N. G., Srivastava, A., Rana, S., & Mahendia, S. (2026). Microwave-assisted synthesis of activated carbon from aerobic combustion of cotton in sesamee oil for high performance supercapacitor. Discover Electrochemistry, 3(1), Article 52. https://doi.org/10.1007/s44373-026-00139-w

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00139-w

Keywords: activated carbon, supercapacitor, microwave-assisted activation, sesame oil, cotton soot, biomass-derived carbon, energy storage, porosity, electrochemical double-layer capacitor, potassium hydroxide activation, specific capacitance, sustainable materials

The choice of CuCo2O4 is grounded in solid electrochemical logic. As a binary transition metal oxide with a cubic spinel architecture, it hosts copper and cobalt cations on distinct lattice sites, each capable of switching between multiple oxidation states, Cu2+/Cu+ and Co3+/Co2+, during reversible Faradaic redox reactions. This rich redox chemistry underpins pseudocapacitance, the mechanism by which charge is stored through fast surface reactions rather than slow bulk diffusion. Compared with conventional cobalt oxides such as Co3O4, CuCo2O4 offers better electronic conductivity, and copper is both cheaper and less toxic than cobalt, an important consideration for any technology hoping to scale up. Yet pristine CuCo2O4 has well-known weaknesses: low surface area, a tendency for nanoparticles to clump together, sluggish ion diffusion through dense structures, and mechanical degradation as the material swells and shrinks during cycling.

The team’s solution was to marry the oxide to a porous carbon scaffold made from agricultural waste. Coconut shells were washed, dried, crushed, and carbonized at 900 degrees Celsius for four hours, yielding an activated carbon powder rich in micropores and mesopores and decorated with oxygen-containing functional groups that bond readily with metal oxide surfaces. The CuCo2O4 itself was synthesized through a sol-gel combustion route, with copper chloride and cobalt precursors chelated by citric acid, gelled, dried, and calcined at 600 degrees Celsius. The final composite was made by physically grinding equal weights of oxide and carbon in an agate mortar, a deliberately simple and low-cost procedure that could easily translate to industrial production.

Structural analysis confirmed the strategy worked at the nanoscale. X-ray diffraction showed sharp, high-intensity peaks matching the cubic spinel phase of CuCo2O4, with only a trace of CuO as a secondary impurity. When the activated carbon was added, the diffraction peaks broadened and weakened, and the average crystallite size shrank from 43.89 nanometers to 33.79 nanometers. That shrinkage matters: the disordered carbon framework physically restrains particle growth and aggregation during synthesis, leaving more electrochemically active sites exposed to the electrolyte. A broad reflection between 20 and 30 degrees in the composite pattern confirmed the amorphous, graphitic character of the biomass-derived carbon dispersed among the spinel nanocrystals.

The most striking transformation appeared in the surface chemistry. Nitrogen physisorption measurements revealed that pristine CuCo2O4 has a modest BET surface area of roughly 20 square meters per gram, with mesopores averaging 25.1 nanometers wide. The composite, by contrast, exploded to 562 square meters per gram, with an average pore width of just 1.9 nanometers and a Type I isotherm characteristic of microporous materials. In practical terms, the carbon scaffold multiplies the electrode’s ion-accessible real estate by a factor of nearly thirty, creating an interconnected network through which electrolyte ions can race rather than crawl. Infrared spectroscopy added further evidence of intimate coupling, showing new carbon-oxygen and aromatic carbon-carbon bands alongside the characteristic Co-O and Cu-O vibrations of the spinel framework.

Electrochemical testing in a three-electrode cell with 3 M potassium hydroxide electrolyte translated these structural gains into performance. Cyclic voltammetry showed broad redox peaks for both materials, but the composite enclosed a far larger current area, delivering 562.5 farads per gram at 5 millivolts per second, a 96 percent jump over the pristine oxide’s 287.5 farads per gram. Galvanostatic charge-discharge measurements were even more emphatic: at a current density of 1 ampere per gram, the composite achieved a specific capacitance of 643.75 farads per gram, against 389.06 farads per gram for CuCo2O4 alone. Even when the current was pushed fivefold to 5 amperes per gram, the composite retained 507.81 farads per gram, demonstrating the rate capability that fast-charging applications demand.

Perhaps the most revealing analysis came from Dunn’s method, which separates surface-dominated capacitive storage from diffusion-limited storage. For pristine CuCo2O4, capacitive contributions ranged from just 11 to 33 percent across the tested scan rates, meaning most of its charge was locked behind slow diffusion. The composite flipped that picture entirely, with capacitive contributions of 55 to 82 percent, confirming that the activated carbon network shifts the electrode toward fast, surface-controlled charge storage. Impedance spectroscopy reinforced the point: solution resistance fell from 8.21 ohms to 4.66 ohms, and charge-transfer resistance collapsed from 2725.45 ohms to 627.87 ohms, reflecting the porous carbon’s role in opening ion pathways and improving electron transport.

Energy and power metrics tell a similarly compelling story. The composite delivered 205.76 watt-hours per kilogram at a power density of 1797.90 watts per kilogram, and still held 162.24 watt-hours per kilogram at 8985.6 watts per kilogram. The pristine oxide managed only 124.5 watt-hours per kilogram initially and lost 42 percent of that at high power. Durability testing at 5 amperes per gram showed the composite retaining 90 percent of its capacitance after 5000 cycles, comfortably ahead of the pure oxide’s 82.5 percent. The authors attribute this resilience to the carbon matrix buffering the mechanical stresses of oxide expansion and contraction, while noting that energy densities calculated from three-electrode tests may not directly translate to full device performance.

What makes this work resonate beyond the laboratory is its sustainability angle. Coconut shells are an abundant, low-cost biomass residue across tropical regions, with high carbon yield and minimal inorganic contamination, making them an ideal feedstock for electrode-grade activated carbon. By pairing waste-derived carbon with a mixed metal oxide whose redox-active cations span multiple oxidation states, the study demonstrates that high-performance energy storage need not depend on exotic or expensive materials. Compared with a previously reported CuCo2O4/reduced graphene oxide electrode that achieved 291 farads per gram, the coconut-shell composite more than doubles that figure while sustaining 90 percent retention over five times as many cycles. As grid buffering, regenerative braking, and portable electronics all demand faster, tougher, and greener storage, this trash-to-treasure electrode offers a template worth watching.

Subject of Research: CuCo2O4/activated carbon composite electrodes for supercapacitor energy storage

Article Title: Enhanced electrochemical performance of CuCo2O4 and CuCo2O4/activated carbon composites for supercapacitor applications

Article References: Franklin, J. B., Venkatesan, J., Paul, J. F. J., Harini, S., Fathima, J. P. R., Sundaram, S. J., & Kaviyarasu, K. (2026). Enhanced electrochemical performance of CuCo2O4 and CuCo2O4/activated carbon composites for supercapacitor applications. Discover Electrochemistry, 3(1), Article 56. https://doi.org/10.1007/s44373-026-00143-0

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00143-0

Keywords: supercapacitors, CuCo2O4, activated carbon, coconut shells, pseudocapacitance, spinel oxide, energy storage, biomass-derived carbon, electrode materials, specific capacitance, electrochemical impedance, sustainable materials

Supercapacitors occupy a unique niche on the energy storage landscape, bridging the gap between traditional capacitors and rechargeable batteries. Where batteries excel at storing large amounts of energy for long durations, supercapacitors deliver exceptional power density, ultrafast charge-discharge kinetics, and an operational temperature range spanning from minus 40 to 85 degrees Celsius. Unlike conventional batteries, they can endure millions of charge-discharge cycles with minimal degradation, making them exceptionally reliable for high-frequency applications. On a Ragone plot, which maps the trade-off between energy density and power density, supercapacitors sit firmly in the high-power regime. This makes them ideal for regenerative braking in electric buses and rail transit, frequency regulation in smart grids, short-term buffering in solar and wind installations, and rapid-charging support in smartphones and wearable electronics. Hybrid systems that pair supercapacitors with batteries are already optimizing energy management in electric vehicles, aerospace platforms, and portable medical devices.

The problem with conventional supercapacitor electrodes is their pedigree. Activated carbon, the workhorse material, is typically derived from coal tar, petroleum pitch, or synthetic polymers, tying an ostensibly green technology directly to fossil fuel extraction. Graphene and carbon nanotubes offer superior conductivity and mechanical integrity, but their large-scale synthesis remains energy-intensive and costly. Worse still, the processing and disposal of materials containing fluorine, sulfur, cyanide groups, or heavy metals carry significant environmental burdens. The review argues that advancing sustainable electrode materials is not merely a scientific challenge but an environmental imperative, and this is precisely where biomass-derived carbons enter the picture, offering a renewable, low-cost, and carbon-neutral alternative that can be engineered with remarkable precision.

The chemistry underlying this transformation is elegant. Lignocellulosic biomass, the structural material of plants, is composed of three biopolymers whose thermal behavior dictates the final carbon architecture. Cellulose, a linear polymer of glucose units making up 35 to 50 percent of the material, decomposes between 260 and 350 degrees Celsius, releasing volatile species such as carbon dioxide, carbon monoxide, methane, and water vapor that carve out micropores in an amorphous carbon framework. Hemicellulose, a branched heteropolymer rich in acetyl and hydroxyl groups, breaks down even earlier, between 180 and 260 degrees Celsius, promoting micropore formation and oxygen doping. Lignin, an aromatic biopolymer, decomposes gradually over 200 to 500 degrees Celsius, condensing into graphitic domains that improve electrical conductivity and mechanical stability. The coexistence of these three components yields hierarchically porous carbon networks combining micropores smaller than two nanometers, mesopores between two and fifty nanometers, and macropores larger than fifty nanometers, a structure that facilitates both electrolyte accessibility and rapid ion transport.

Beyond porosity, biomass brings a built-in doping chemistry that conventional precursors cannot match. Algal biomass, rich in proteins and amino acids, introduces nitrogen in pyridinic, pyrrolic, and graphitic configurations, along with sulfur dopants, all of which enhance redox activity and conductivity. Food waste contributes phosphorus species that expand interlayer spacing and improve surface polarity and wettability. Even the inorganic constituents play a role: potassium carbonate and calcium carbonate act as in-situ activation catalysts through carbothermal reduction reactions, while silica species provide rigid templates that define mesoporous channels before being washed away. The numbers emerging from this approach are striking. A nitrogen-doped hierarchical porous carbon reported in the review achieved an ultrahigh specific surface area of 3,142 square meters per gram and an energy density of 88 watt-hours per kilogram with only 9 percent capacitance loss over 10,000 cycles. A nitrogen-phosphorus-sulfur co-doped carbon derived from peanut meal delivered a specific capacitance of 525 farads per gram, retaining 68 percent of that value even at ten times higher current density.

Synthesis routes matter enormously, and the review dissects them with technical rigor. Pyrolysis, heating biomass in an oxygen-free atmosphere at 300 to 1,200 degrees Celsius, promotes graphitization and conductivity at high temperatures while preserving oxygen-containing functional groups that improve wettability at lower temperatures. Hydrothermal carbonization, which treats biomass in water under high pressure, offers a greener, lower-temperature route that retains oxygen functionalities, making it suitable for flexible, binder-free, solid-state devices. In one standout example, researchers combined hydrothermal carbonization with chemical activation to create a 3D-printed electrode from poplar sawdust that mimicked wood’s vascular patterns, achieving a specific surface area of 253 square meters per gram and an areal capacitance of 7.95 farads per square centimeter at a mass loading of 17 milligrams per square centimeter. Activation, whether physical using steam or carbon dioxide, or chemical using potassium hydroxide, zinc chloride, or phosphoric acid, remains the decisive step for unlocking high surface areas, though the review notes that corrosive chemical activation poses environmental concerns of its own.

Some of the most creative work dispenses with external chemicals entirely through self-activation and bio-inspired templating. Platycladus orientalis leaves were converted in a single step into nitrogen-oxygen-sulfur co-doped hierarchical porous carbon, with the plant’s own bioactive elements driving simultaneous carbonization, doping, and pore formation. Transgenic technology has even entered the field: researchers regulated the SlHDA3 gene in tomato stems to modify their cellular structure before carbonization, yielding a material that achieved a specific capacitance of 201.6 farads per gram and an energy density of 11 watt-hours per kilogram in a symmetric device. A spider web-inspired three-dimensional carbon network built on metal-organic framework templates reached 395 farads per gram and successfully powered 19 red LED lights. Meanwhile, hydrogen-bonded organic framework templates converted heavy bio-oil into flower-like carbon architectures delivering 117.5 watt-hours per kilogram in zinc-ion hybrid supercapacitors, and ice-templating produced hollow carbon cages with hierarchical porosity for the same application.

The waste-to-wealth case studies read like a catalog of unlikely hero materials. Cooked chicken bones, activated to an ultrahigh surface area of 2,235.8 square meters per gram, delivered a capacitance of 329.41 farads per gram with 99.8 percent coulombic efficiency and 90.1 percent retention after 20,000 cycles. Chicken fat oil was transformed into multilayered graphitic carbon nano-onions via simple flame pyrolysis, and sulfur-nitrogen doping pushed their capacitance to 261 farads per gram, enabling an asymmetric device with 32.8 watt-hours per kilogram energy density. A dual-precursor strategy combining hydrochar with polymerized bio-tar produced an interconnected mesoporous network with a surface area of 2,714 square meters per gram and 88.6 percent retention after 5,000 cycles. Daylily, an edible herb, yielded nitrogen-phosphorus co-doped carbons with 299.1 farads per gram and 99.6 percent retention after 4,000 cycles. Even human hair has found a role as a conductive scaffold, supporting silver and nickel-doped manganese oxide composites that reached 1,770 farads per gram in a hybrid supercapacitor.

Hybridization with pseudocapacitive materials represents perhaps the most powerful design strategy, bridging the gap between battery-like energy and capacitor-like power. A nickel-cobalt layered double hydroxide heterostructure anchored on pomelo peel-derived porous carbon delivered an extraordinary 3,290 farads per gram, and the assembled asymmetric device achieved 51 watt-hours per kilogram with a peak power density of 16 kilowatts per kilogram. Biomass-derived carbon nanosheets encapsulating iron oxide nanoparticles retained 99.6 percent of their capacitance after 100,000 cycles, with a redox additive doubling the energy density to 32 watt-hours per kilogram. Aloe vera gel served as a natural reducing agent for green synthesis of cobalt oxide nanostructures, eliminating toxic chemicals while achieving 468 farads per gram. These results demonstrate that biomass-derived carbons function not merely as cheap substitutes but as sophisticated conductive scaffolds that buffer structural strain, facilitate charge transport, and enable rapid ion diffusion in next-generation composite electrodes.

Significant hurdles remain before banana peels and bone ash power our grids. Feedstock variability leads to inconsistent carbon yields and electrochemical performance, making process standardization difficult. Chemical activation demands high energy input and generates hazardous by-products, and achieving uniform pore size distribution and precise dopant control across batches is still elusive. Flexible and wearable applications require freestanding films rather than binder-bound powders. The review’s authors propose a clear roadmap: scalable continuous processing integrated into existing agro-industrial supply chains such as rice mills and sugar refineries, green activation methods, standardized performance metrics, life-cycle and techno-economic assessments, and prototype-scale validation. If those pieces fall into place, biomass-derived carbons could deliver a rare double win in the energy transition, simultaneously diverting waste from landfills and storing the renewable electricity that will replace fossil fuels, one charge at a time.

Subject of Research: Biomass-derived carbon materials for sustainable supercapacitor electrodes

Article Title: From biomass to energy storage: sustainable carbon materials for next-generation supercapacitors

Article References: Merum, D., & Kang, M. (2025). From biomass to energy storage: sustainable carbon materials for next-generation supercapacitors. Advances in Industrial and Engineering Chemistry, 1(1), Article 26. https://doi.org/10.1007/s44405-025-00028-7

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00028-7

Keywords: supercapacitors, biomass-derived carbon, activated carbon, heteroatom doping, pyrolysis, hydrothermal carbonization, porous materials, energy storage, waste valorization, circular economy, electric double-layer capacitor, renewable energy

The team began with balsa wood, a precursor prized for its very low density of roughly 0.1 grams per cubic centimeter, high porosity, and well-defined anatomical anisotropy. Natural wood is anything but uniform: its axial direction runs parallel to tree growth and exposes honeycomb-like cellular channels, its radial direction reveals the extended planar surfaces of wood ray lamellae, and its tangential direction presents a more homogeneous network punctuated by lenticular ray cross-sections. Previous studies of wood-derived carbon absorbers had largely confined their measurements to a single direction, leaving the link between this inherent structure and electromagnetic response poorly understood. The new work set out to establish that structure–electromagnetic correlation directly.

To fabricate the material, the researchers first delignified the wood using an acidified sodium chlorite treatment, removing lignin and part of the hemicellulose, then freeze-dried the result to obtain a wood sponge. Carbonization at 680 degrees Celsius under flowing argon produced the wood carbon sponge, a structure just 0.035 grams per cubic centimeter in density. During freezing, ice crystals preferentially nucleated in the water-rich wood rays, expanding and compressing neighboring fiber cells until the honeycomb pores closed, generating an undulating, arch-shaped lamellar architecture. The carbon sponge was then impregnated under vacuum with a methyltrimethoxysilane-derived organosilica sol, gelled, aged, solvent-exchanged, and dried at ambient pressure, yielding the composite, which rises to about 0.13 grams per cubic centimeter but fully preserves the anisotropic skeleton, with silica nanoparticles uniformly filling the interlayer voids.

An extensive characterization campaign confirmed the design. Scanning electron microscopy revealed the distinct lamellar, fused-fiber, and ray-lamellae structures along the three anatomical axes, while three-dimensional micro-CT showed homogeneous dispersion of the organosilica phase across the entire millimeter-scale monolith. Nitrogen adsorption and mercury intrusion porosimetry showed that the pure carbon sponge is dominated by micropores around 2 nanometers formed during pyrolysis, whereas the composite develops a broad mesoporous network spanning roughly 2 to 100 nanometers. Infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy together tracked the removal of lignin, the conversion of cellulose into partially graphitized amorphous carbon, and the successful incorporation of the silica network through characteristic Si–O–Si and Si–CH3 signatures.

Electromagnetic testing over 2 to 18 gigahertz using the coaxial transmission line method exposed a robust directional ordering: complex permittivity was consistently highest in the tangential direction, intermediate in the radial direction, and lowest in the axial direction. In the tangential orientation, the electric field drives charge carriers unimpeded along continuous conductive lamellar planes, producing an overdeveloped conductive network, severe impedance mismatch, and an interface reflection coefficient approaching 39 percent at 2 gigahertz. Along the axial direction, charge transport is repeatedly interrupted by interlayer interfaces, so conductivity and dielectric loss are low even though waves enter easily. The radial direction proved the sweet spot: the undulating, arch-shaped lamellae force incident waves through multiple internal reflections and scattering, prolonging propagation paths and creating abundant polarization sites without forming an overly continuous conductive network.

The silica aerogel played a dual regulatory role. Acting as a low-permittivity phase, it diluted and partially disrupted the excessive conductive network, shifting impedance matching toward the ideal range in all three directions. Simultaneously, the newly created carbon/silica heterogeneous interfaces served as additional polarization centers, intensifying interfacial polarization relaxation and boosting dielectric loss. The results were striking: the composite’s tangential direction, previously the worst absorber, achieved a minimum reflection loss of −64.1 decibels at a thickness of 3.15 millimeters, while the radial direction delivered an effective absorption bandwidth of 11.6 gigahertz at only 4.95 millimeters of thickness, fully covering the X and Ku bands and outperforming most reported carbon aerogels.

Quantitative analysis based on Debye relaxation theory separated the dielectric loss into conduction and polarization components, confirming these interpretations. Cole–Cole plots showed that the pure sponge’s tangential direction was dominated by polarization loss from surface charge accumulation, while the radial and axial directions were conduction-dominated at low frequencies and increasingly polarization-driven at higher frequencies. After silica incorporation, the polarization-to-conduction loss ratio rose in the radial and axial directions, reflecting the new heterogeneous interfaces and dipole sites, while falling in the tangential direction as alleviated impedance mismatch allowed interior conductive networks to be activated. A quarter-wavelength interference model further showed that absorption peaks aligned precisely with theoretical matching thicknesses, validating the underlying cancellation mechanism. Radar cross-section simulations on coated metal plates indicated that the composite in the tangential orientation kept monostatic radar signatures below −10 decibel square meters across angles from −80 to 80 degrees, underscoring its practical stealth potential.

Beyond electromagnetic performance, the composite excelled as a thermal insulator and a resilient mechanical structure. Thermal conductivity dropped from 0.054, 0.048, and 0.044 watts per meter-kelvin in the axial, radial, and tangential directions of the pure sponge to 0.040, 0.038, and 0.037 watts per meter-kelvin in the composite, with the nanoporous silica network suppressing gas conduction through the Knudsen effect and forcing heat along tortuous solid pathways. Placed on a 150-degree-Celsius hot stage, the tangential face of the composite rose only to 32.2 degrees Celsius after five minutes. Mechanically, the tangential direction behaved elastically, sustaining 50 percent strain, and after silica reinforcement it carried 419 kilopascals at that strain, roughly ten times the unreinforced value. After 50 loading-unloading cycles at 50 percent strain, the sample retained 92.3 percent of its height with stable energy dissipation, evidence of durable compressibility and resilience.

The broader significance of the work lies in its demonstration that nature’s own architecture can serve as a design parameter rather than a limitation. By preserving and exploiting the anisotropic cellular structure of wood, and then tuning it with a judiciously chosen dielectric filler, the researchers showed that electromagnetic, thermal, and mechanical responses can be engineered simultaneously and selected direction by direction according to application needs. The tangential orientation offers the best thermal insulation and mechanical compliance, the radial orientation delivers unmatched broadband absorption, and the axial orientation provides easy wave entry with moderate loss. This application-oriented customization points toward a new generation of lightweight, sustainable, multifunctional composites for radar stealth, electromagnetic compatibility, and thermal protection, all rooted in one of humanity’s oldest and most renewable materials.

Subject of Research: Wood carbon sponge/silica aerogel composites with anisotropic broadband microwave absorption, elastic resilience, and thermal insulation

Article Title: Wood Carbon Sponge/SiO2 Aerogel Composites with Anisotropic Broadband Microwave Absorption, Elastic Resilience, and Thermal Insulation

Article References: Sun, S., Zhao, Z., Zhan, W., Jiang, Y., Liu, F., Hu, Y., Feng, J., & Feng, J. (2026). Wood Carbon Sponge/SiO 2 Aerogel Composites with Anisotropic Broadband Microwave Absorption, Elastic Resilience, and Thermal Insulation. Advanced Science, Article e77888. https://doi.org/10.1002/advs.77888

Image Credits: AI Generated

DOI: 10.1002/advs.77888

Keywords: wood carbon sponge, silica aerogel, microwave absorption, anisotropic materials, biomass-derived carbon, thermal insulation, radar stealth, impedance matching, interfacial polarization, balsa wood, carbon aerogel, lightweight composites