The study, published in Biomedical Microdevices, describes a multiplexed aptasensor built on a humble cellulose substrate. Led by Jagriti Narang, with Saumitra Singh, Anam Ayaz, Osheen Ansari, and Humaira Farooqi as co-authors, the team inscribed carbon and silver electrodes directly onto paper using screen-printing techniques, creating a flexible, lightweight sensing platform that requires no expensive laboratory infrastructure to manufacture. The device features two independently functionalized working electrodes, each dedicated to a different disease biomarker, allowing a single measurement session to interrogate both Alzheimer’s-associated and Parkinson’s-associated proteins at once.

The two targets at the heart of the sensor are amyloid beta-42, the peptide fragment notorious for aggregating into the plaques that define Alzheimer’s disease, and alpha synuclein-60, a protein species linked to the Lewy body pathology characteristic of Parkinson’s disease. Both molecules circulate at vanishingly low concentrations in biological fluids, which is precisely why conventional diagnostic approaches struggle. Detecting them reliably demands a sensing interface that can amplify vanishingly small molecular events into measurable signals—something the Indian team achieved through a clever combination of nanomaterials and biological recognition elements.

The amplification strategy centers on zinc oxide nanorods, which the researchers grew onto the carbon working electrodes to dramatically increase the effective surface area available for biomolecule immobilization. Zinc oxide is a favorite material in biosensor engineering for good reason: it is biocompatible, electrically conductive, and its high isoelectric point makes it an excellent scaffold for anchoring proteins and nucleic acids. By decorating the nanorod-covered electrodes with target-specific DNA aptamers—short, synthetic single-stranded DNA sequences that fold into precise three-dimensional shapes capable of binding a single molecular target with antibody-like specificity—the team created two distinct biorecognition surfaces on one chip.

The readout method is electrochemical impedance spectroscopy, a label-free technique that measures how much a surface resists the transfer of electrons in solution. In the sensor’s baseline state, a small redox probe can shuttle freely between the electrode and the surrounding electrolyte. When the target protein—amyloid beta-42 on one electrode, alpha synuclein-60 on the other—binds to its aptamer, the bulky protein layer physically blocks that electron transfer, increasing what electrochemists call the charge-transfer resistance. The magnitude of that increase scales with the concentration of the target, so a simple impedance measurement translates directly into a quantitative biomarker reading, with no chemical labels, enzymes, or secondary reagents required.

The performance figures are striking for a paper-based platform. The sensor exhibited a linear response spanning five orders of magnitude, from 0.1 nanograms per milliliter up to 10 micrograms per milliliter, for both biomarkers. The limits of detection came out at 4.41 nanograms per milliliter for amyloid beta-42 and 2.62 nanograms per milliliter for alpha synuclein-60—concentrations low enough to be relevant for physiological monitoring. Equally important, the team demonstrated that the device retains its responsiveness in artificial cerebrospinal fluid and artificial saliva, two physiologically mimicked matrices that are far messier than a clean buffer solution. Saliva, in particular, is an attractive sample type for decentralized testing because it can be collected non-invasively by patients themselves, without needles or clinical staff.

Multiplexing is the quiet innovation here. Most existing biosensors detect a single biomarker, but neurodegenerative diseases do not present as single-molecule problems. Alzheimer’s and Parkinson’s share overlapping symptoms, overlapping pathologies, and in many patients overlapping diagnoses, and clinicians increasingly recognize that distinguishing between them—or catching both—requires looking at multiple molecular indicators in parallel. By building two independently addressable working electrodes onto one paper strip, the researchers created a platform where a single drop of sample could, in principle, yield a two-disease molecular profile simultaneously, at a fraction of the cost of running separate assays.

The broader context makes the work timely. Paper-based microfluidics and screen-printed electrodes have surged in popularity over the past decade because they promise something the diagnostics industry has long struggled to deliver: laboratory-quality molecular testing at a price point and form factor suitable for clinics in resource-limited settings, pharmacies, and eventually the home. The COVID-19 pandemic demonstrated both the demand for and the feasibility of rapid, disposable biosensing, and researchers worldwide have been racing to apply the same design philosophy to chronic diseases, where early detection could shift the entire trajectory of patient care. Electrochemical aptasensors, which pair the stability and synthetic ease of DNA with the sensitivity of electrochemical transduction, have emerged as one of the most promising routes.

The authors are candid about the distance between proof of concept and clinical deployment. Their abstract explicitly flags the hurdles that remain: the low concentrations of neurodegenerative biomarkers in real samples, interference from the complex protein mixtures in genuine biological fluids, nonspecific adsorption of off-target molecules onto the sensor surface, variability from sensor to sensor, and questions of long-term storage stability. The current results were obtained in artificial matrices rather than real patient samples, and the team acknowledges that optimization of surface immobilization chemistry, antifouling behavior, and sensitivity—followed by validation using real clinical saliva and cerebrospinal fluid—will be required before the platform can approach practical diagnostic use.

Those caveats are standard for early-stage biosensor research, and they do not diminish the significance of what has been demonstrated. What the Jamia Hamdard team has built is a complete architectural template: a disposable paper substrate, printed carbon and silver electrodes, nanostructured signal amplification, aptamer-based molecular recognition, and label-free impedance readout, all integrated into a multiplexed format targeting two of the most consequential proteins in neurodegeneration. If subsequent studies can carry that architecture through clinical validation, the vision of a cheap paper strip that screens for Alzheimer’s and Parkinson’s in a doctor’s office—or even at home—moves a meaningful step closer to reality, and the growing global burden of these diseases gains a potential new line of early defense.

Subject of Research: A multiplexed paper-based impedimetric aptasensor using zinc oxide nanorods for simultaneous detection of Alzheimer's and Parkinson's disease biomarkers

Article Title: Multiplexed impedimetric zinc oxide nanorods-modified aptasensor on carbon ink-inscribed paper electrodes for the specific and sensitive co-detection of Alzheimer’s and Parkinson’s disease

Article References: Multiplexed impedimetric zinc oxide nanorods-modified aptasensor on carbon ink-inscribed paper electrodes for the specific and sensitive co-detection of Alzheimer’s and Parkinson’s disease. (n.d.). https://doi.org/10.1007/s10544-026-00855-5

Image Credits: AI Generated

DOI: 10.1007/s10544-026-00855-5

Keywords: Alzheimer's disease, Parkinson's disease, biosensor, aptasensor, zinc oxide nanorods, electrochemical impedance spectroscopy, amyloid beta-42, alpha synuclein, paper-based diagnostics, point-of-care testing, multiplexed sensing, neurodegenerative diseases

A team reporting in Advanced Science has now tackled this problem not with yet another surface coating, but with something arguably more valuable to the field: a standardized, modular operating procedure that turns lithium pretreatment from an empirical art into a reproducible protocol. The work decomposes lithium surface preparation into three functionally distinct modules—chemical etching (E), mechanical brushing (B), and solution soaking (S)—and then systematically recombines them to identify which sequence produces the most stable interface. The result is a pre-assembly recipe, the integrated E–B–S sequence, that transforms lithium from an ill-defined material into a surface-defined system suitable for rigorous comparison across laboratories.

The diagnostic platform for evaluating the procedure was the symmetric Li||Li cell, in which two identically treated lithium electrodes face each other. This configuration isolates the lithium interface from complications introduced by foreign substrates or cathode-side limitations. The researchers compared single-step and partial combinations of the modules against the full E–B–S sequence, using the time required for cell voltage to diverge to ±0.5 V as a practical indicator of interfacial degradation. Partial treatments consistently showed earlier voltage amplification and larger fluctuations, while the fully integrated sequence maintained stable, reproducible voltage profiles over extended cycling. Importantly, the effects proved synergistic rather than simply additive: soaking directly after etching can produce non-uniform interphase formation on a freshly exposed, highly reactive surface, whereas the intermediate brushing step homogenizes the etched surface before the artificial interphase is built, enabling more continuous interfacial coverage.

Imaging before and after cycling revealed how deeply the starting condition shapes subsequent degradation. As-received lithium, with its heterogeneous, striated surface, developed rough, dendritic-like protrusions after repeated plating and stripping. Etching alone smoothed the initial surface but failed to suppress deterioration during cycling; cross-sectional microscopy showed large, continuous cracks extending through the electrode. In contrast, lithium treated with the full E–B–S sequence retained a flat, continuous morphology even after prolonged operation, with a denser interfacial region and markedly reduced cracking and porosity. Using a lithium-sensitive, windowless energy-dispersive X-ray detector, the team directly visualized lithium redistribution across the cross-section, distinguishing redeposited lithium from the bulk and confirming that elemental distributions of lithium, fluorine, phosphorus, oxygen, carbon, and sulfur were far more spatially uniform in the SOP-treated electrodes.

Atomic force microscopy added a quantitative and somewhat counterintuitive geometric dimension to the story. As-received lithium showed a root-mean-square roughness of about 61 nm with a surface area difference of only roughly 1.1 percent, meaning its effective geometric area barely exceeded its projected area. Etching reduced roughness to about 30 nm while barely changing the area, confirming its role as a leveling step. Brushing, however, transformed the surface into a three-dimensionally corrugated landscape, raising roughness to roughly 253 nm and the surface area difference to about 18.8 percent. After the complete sequence, roughness climbed further to approximately 430 nm and the surface area difference reached about 44.7 percent, indicating that the soaking-formed interphase conforms to and preserves the high-area topology rather than flattening it. This expanded effective area lowers the local current density under a given applied current—a structurally favorable starting point for suppressing dendrite-driving hotspots.

Electrochemical impedance spectroscopy tracked how interfacial resistance evolved over 100 hours of cycling. As-received lithium began with a large interphase resistance, showed a temporary early-cycling decrease as the interface reorganized, and then suffered marked resistance growth as degradation took hold. The E–B–S-treated electrodes displayed a substantially lower initial interphase resistance and kept both interphase and charge-transfer resistances comparatively stable, with far smaller increases after 100 hours. The treated cells also maintained lower electrolyte resistance throughout, suggesting a more stable electrolyte–interface environment in which the electrode itself is less prone to triggering electrolyte decomposition.

The chemistry behind the etching step proved equally important. The researchers tested three polycyclic aromatic hydrocarbons—pyrene, naphthalene, and biphenyl—dissolved in tetrahydrofuran as etching agents. Density functional theory calculations showed that binding strength between lithium and the aromatic molecules increases with π-conjugation, following the trend pyrene greater than naphthalene greater than biphenyl. Pyrene, with the strongest affinity, stripped lithium fastest and produced cells that failed within roughly 2800 to 3000 minutes. Biphenyl, with moderate interaction strength, removed native surface layers without aggressive lithium loss, yielding the most homogeneous surfaces and the longest cycling lifetimes, exceeding 6000 minutes. The lesson is that controlled etching requires a chemical Goldilocks zone: enough affinity to clean the surface, not so much that it consumes the metal.

For the soaking module, the team compared lithium nitrate, lithium TFSI, and lithium FSI salts in dimethoxyethane. Depth-resolved X-ray photoelectron spectroscopy revealed distinct interphase chemistries: nitrate treatment produced nitrogen-rich inorganic species such as lithium nitride, while LiTFSI generated lithium fluoride mainly near the surface, fading rapidly with depth. LiFSI, by contrast, promoted a lithium fluoride–rich interphase extending from the surface into the subsurface regions of the corrugated lithium. Given lithium fluoride’s high chemical stability and mechanical robustness, this spatially extended distribution offers continuous coverage that suppresses parasitic reactions and maintains interfacial integrity through repeated plating and stripping—consistent with the reduced polarization growth observed electrochemically.

The ultimate test came in practical full cells pairing the treated lithium anodes with lithium iron phosphate cathodes. After 200 cycles at 0.5 C, cells with as-received lithium retained only 39.6 percent of their initial capacity, while cells using E–B–S-treated lithium retained 90.2 percent. Overpotential told a parallel story: by the 150th cycle, the as-received cell’s overpotential had grown from 79 to 210 mV, whereas the SOP-treated cell rose only from 72 to 116 mV. Rate capability widened the gap further—at 2 C, the treated cells delivered 127 mAh per gram versus 106 mAh per gram for untreated lithium. The benefits persisted under demanding conditions, including 50-micrometer calendered thin lithium foils with reduced inventory, and preliminary lithium–sulfur cells built with SOP-treated thin lithium delivered specific capacities of 1192 and 1035 mAh per gram at 0.1 C and 0.2 C respectively, demonstrating cross-chemistry applicability.

Beyond the immediate performance gains, the significance of this work lies in standardization itself. Because etching, brushing, and soaking are physically separated and independently tunable, the framework is potentially compatible with continuous or roll-to-roll lithium processing, though the authors note that challenges such as etching-solution aging, solvent recovery, brush wear, and soaking-solution drift must be resolved before assembly-line implementation. More broadly, by minimizing the uncontrolled variability that has long plagued lithium metal research, the modular SOP enables genuinely meaningful comparison across studies—whether lithium serves as the working anode or merely as the counter and reference electrode whose surface condition quietly propagates uncertainty through otherwise well-controlled experiments. It is a reminder that in electrochemistry, as in any science, reproducibility begins before the experiment starts: with the disciplined preparation of the material itself.

Subject of Research: A modular standard operating procedure for standardizing lithium metal electrode interfaces in rechargeable batteries

Article Title: A Modular Standard Operating Procedure for Standardizing Lithium Metal Interfaces

Article References: Chang, W.-H., Shaju, A., Lin, H.-S., Hsu, S.-L., Dinh, Q. H., Yeh, C.-N., Li, E. Y.-T., & Su, Y.-S. (2026). A Modular Standard Operating Procedure for Standardizing Lithium Metal Interfaces. Advanced Science, 13(56), Article e76595. https://doi.org/10.1002/advs.76595

Image Credits: AI Generated

DOI: 10.1002/advs.76595

Keywords: lithium metal anode, solid electrolyte interphase, battery standardization, chemical etching, biphenyl, LiFSI, lithium fluoride, dendrite suppression, electrochemical impedance spectroscopy, LiFePO4 full cells, lithium–sulfur batteries, reproducibility

The team fabricated two distinct compositions: Sr0.9Fe0.1TiO3, in which iron replaces strontium on the A-site of the perovskite lattice, and SrTi0.9Fe0.1O3, in which iron replaces titanium on the B-site. This site-specific comparison is the conceptual heart of the study. Because Fe3+ and Ti4+ carry different charges, substituting iron into the titanium site forces the lattice to compensate by creating oxygen vacancies, the very defects that make water dissociation possible. A-site substitution, by contrast, introduces greater lattice distortion because the ionic radius of iron is far smaller than that of strontium, generating compressive strain and dislocations that reshape the material’s surface chemistry in a different way.

The synthesis itself is deliberately simple. High-purity strontium carbonate, iron oxide and titanium dioxide powders were ground together in acetone for two hours in the molar ratios required for each composition, then calcined in air at 800 degrees Celsius for sixteen hours. This high-temperature treatment is not merely a way to fuse the precursors; it is a defect-engineering step that deliberately generates pores, structural imperfections and oxygen vacancies throughout the material. The powders were then mixed with a polyvinyl alcohol binder, pressed into square pellets of two by two centimetres with a thickness of just one millimetre under six tons of pressure, and sintered at 900 degrees Celsius for four hours to strengthen them and multiply the defect population further.

Characterisation confirmed that the doping strategy worked as intended. X-ray diffraction showed clean cubic perovskite phases with no residual iron oxide impurities, indicating that iron atoms had genuinely entered the strontium titanate lattice. Rietveld refinement using the cubic space group Pm-3m revealed average crystallite sizes of 26.70 nanometres for the A-site-doped compound and 30.99 nanometres for the B-site-doped version, both firmly in the nanoscale regime. Raman spectroscopy delivered the most telling evidence: a strong peak near 695 wavenumbers, characteristic of oxygen vacancies, appeared in both materials, alongside first-order vibrational modes that only become visible when the ideal crystal symmetry is broken by impurities and defects.

Electron microscopy added the third ingredient for successful water splitting: porosity. Field-emission scanning electron micrographs revealed spherical grains of varying sizes, with average grain diameters of 0.13 micrometres for Sr0.9Fe0.1TiO3 and 0.17 micrometres for SrTi0.9Fe0.1O3, together with irregularly shaped tiny pores attributed to the iron incorporation during high-temperature sintering. The smaller grains of the A-site-doped material provide a larger surface area, and therefore more reactive sites where water molecules can adsorb and dissociate. Energy-dispersive X-ray spectra confirmed the presence of strontium, titanium, iron and oxygen, with no detectable contaminants.

The working mechanism of the cell is a cascade of surface chemistry. When water first touches the defect-rich pellet, uncoordinated titanium ions on the surface act as Lewis acid sites, accepting lone-pair electrons from the oxygen atoms of polar water molecules, while neighbouring lattice oxygen atoms act as Lewis base sites. This synergistic acid-base interaction drives chemidissociation, cleaving water into hydroxide and hydronium ions. Additional water molecules then physisorb on top of this first layer through hydrogen bonding, forming a continuous network through which protons travel by the Grotthuss hopping mechanism, passing from one molecule to the next. Protons trapped inside pores generate a high local electrostatic potential that dissociates even more water molecules in the physisorbed layers, amplifying the effect.

Once the ions exist, the electrodes take over. Hydroxide ions migrate toward a zinc sheet anode attached to the back of the pellet, where they form zinc hydroxide and release free electrons that flow through the external circuit. Meanwhile, hydronium ions travel to a comb-shaped silver cathode painted on the front face, where they gain electrons and are reduced to hydrogen gas and water. The silver comb pattern maximises charge-collection area, and the entire redox couple proceeds without any added acid, alkali or electrolyte. The cell is, in effect, a battery that is activated by water rather than charged by one.

The electrical results are striking for such small devices. A Sr0.9Fe0.1TiO3 cell delivered an open-circuit voltage of 0.9 volts, a peak current of 3.38 milliamperes and a maximum power of 3.04 milliwatts, while the SrTi0.9Fe0.1O3 cell produced 0.83 volts, 3.23 milliamperes and 2.68 milliwatts. The A-site-doped composition outperformed its B-site counterpart, which the authors attribute to its more porous microstructure and lower internal resistance. Electrochemical impedance spectroscopy reinforced this picture: Nyquist plots fitted with equivalent circuits showed lower bulk and charge-transfer resistances for Sr0.9Fe0.1TiO3, at 485.21 and 286.67 ohms respectively, compared with 984.76 and 354.14 ohms for SrTi0.9Fe0.1O3, indicating smoother charge transport when iron substitutes on the strontium site.

The voltage-current polarisation curves also revealed the familiar signatures of real electrochemical devices, including activation losses at the electrode interfaces, ohmic losses from ionic resistance within the porous structure, and mass-transport losses at high current densities where ions accumulate at the electrodes. That these regions appear at all suggests the hydroelectric cells behave like genuine fuel cells in miniature, governed by the same fundamental constraints, and points the way toward systematic optimisation of porosity, defect density and electrode design.

The broader significance lies in what the technology does not require. No harmful gases are emitted, no scarce catalysts are consumed, and the only input is less than a millilitre of water per measurement. While the milliwatt-scale outputs are modest compared with conventional generators, the study establishes a clear design principle: that site-selective doping of perovskite oxides can tune oxygen vacancy formation and, with it, the efficiency of spontaneous water dissociation. If defect engineering can push power densities higher, hydroelectric cells built from iron-doped strontium titanate could one day serve as clean, on-demand power sources for sensors, emergency devices and off-grid electronics, all fuelled by the most abundant molecule on Earth.

Subject of Research: Defect-engineered Fe-doped SrTiO3 perovskite hydroelectric cells that generate electricity via room-temperature water splitting

Article Title: Fe-doped SrTiO3 based perovskite hydroelectric cells for electricity generation via room temperature water splitting

Article References: Kajal, Bharti, A., Saini, R., Jyoti, N., Sharma, A., Anand, A., & Kumar, R. (2026). Fe-doped SrTiO3 based perovskite hydroelectric cells for electricity generation via room temperature water splitting. Discover Chemistry, 3(1), Article 474. https://doi.org/10.1007/s44371-026-00923-y

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00923-y

Keywords: hydroelectric cell, strontium titanate, perovskite, oxygen vacancies, water splitting, iron doping, green electricity, defect engineering, Grotthuss mechanism, energy harvesting, solid-state synthesis, electrochemical impedance spectroscopy

The researchers set out to answer a deceptively simple question: what happens to the structure and electrical behavior of yttria-stabilized zirconia when you swap in increasing amounts of cerium? To find out, they fabricated a series of ceria-doped YSZ powders containing between 5 and 30 mole percent cerium. Crucially, they used a water-free co-precipitation method carried out in an ethanol solution under the influence of triethylamine. This unusual synthesis route matters because conventional aqueous precipitation can introduce unwanted hydroxyl groups and inhomogeneity; the alcohol-based approach gives tighter chemical control over how the cerium and zirconium ions precipitate together, producing a more uniform precursor that transforms into a cleaner final ceramic.

Structural analysis confirmed that every composition in the series, from the lowest to the highest cerium loading, formed a pure fluorite structure, the cubic crystal framework that gives stabilized zirconia its useful ionic conduction pathways. As cerium was incorporated, the lattice expanded, a direct consequence of the larger ionic radius of cerium compared with zirconium, and the concentration of defects in the crystal rose. Those defects, chiefly oxygen vacancies, are the very charge carriers that allow oxide ions to hop through the lattice, so their creation is the fundamental reason doping can boost conductivity at all.

But the story quickly became more subtle. The crystallite size of the powders grew steadily from 18 nanometers to 26.7 nanometers as the cerium content increased up to 20 mole percent, then reversed course and shrank to 17.5 nanometers at 30 mole percent. That reversal came with a corresponding increase in lattice strain, a signature that the crystal lattice is being squeezed and distorted. The authors interpret this as evidence of defect interactions at high cerium contents: when dopant ions and vacancies become too numerous, they begin to associate with one another, clustering and straining the lattice rather than remaining freely dispersed. In other words, more dopant does not simply mean more mobile charge carriers.

Microstructure proved to be the second half of the puzzle. Electron microscopy of the sintered ceramics showed that the composition with 10 mole percent cerium, dubbed 10 CYSZ, achieved the best density, with a uniform grain structure and reduced pore density. Once the cerium content climbed above 10 mole percent, the picture deteriorated: grains became heterogeneous in size and shape, and pore density increased. Porosity is the enemy of an electrolyte, because pores block ionic pathways and can allow gas crossover in a working fuel cell. The microstructural data thus pointed to 10 mole percent as the compositional optimum long before any electrical measurement was made.

Electrochemical impedance spectroscopy, a technique that separates the resistive contributions of grains, grain boundaries, and electrodes by probing how the material responds to alternating current across a range of frequencies, delivered the decisive verdict. The ionic conductivity of the ceria-doped samples varied non-monotonically with cerium content, rising to a peak and then falling. The 10 CYSZ composition delivered the highest ionic conductivity of the series: 0.078 siemens per centimeter at 850 degrees Celsius and 0.027 siemens per centimeter at 700 degrees Celsius. It also exhibited the lowest activation energy, 0.85 electronvolts, meaning its oxide ions move through the lattice with the least thermal assistance required. Lower activation energy is precisely what a material needs to perform well at the intermediate temperatures targeted for next-generation fuel cells.

To understand why the conductivity peaked rather than climbing indefinitely, the team combined defect-chemistry analysis based on the nominal dopant content with X-ray photoelectron spectroscopy measurements of the cerium oxidation states. The XPS data revealed the fraction of cerium present as Ce3+ rather than Ce4+, which matters because the reduction of cerium from the 4+ to the 3+ state generates additional oxygen vacancies. The combined analysis showed that while the total oxygen vacancy concentration increases monotonically with ceria content, the effective mobile vacancy fraction inferred from the measured conductivity reaches a maximum at intermediate cerium content. At high doping levels, the authors conclude, vacancies become trapped through association with dopant ions, forming pairs and clusters that are present but immobile. A vacancy that cannot move cannot carry current, no matter how many of them there are.

The study added one more layer of analytical rigor through distribution of relaxation time analysis, a mathematical deconvolution of impedance spectra that resolves overlapping electrochemical processes into distinct characteristic timescales. This analysis confirmed that ionic transport in the ceria-doped zirconia depends critically on both defect chemistry and microstructure, and that these two factors reach their optimum balance at 10 mole percent cerium content. Neither factor alone tells the full story: a material with abundant mobile vacancies but poor sintered density will underperform, and so will a dense ceramic whose vacancies are locked in association complexes. The 10 CYSZ composition threads the needle between the two.

The broader significance of the work lies in its message for how electrolyte materials should be designed. Much of the literature on doped zirconia has pursued the intuition that adding more dopant, or adding sintering aids to densify the ceramic, will reliably improve performance. This study demonstrates that the relationship between dopant content and conductivity is fundamentally non-monotonic, governed by a competition between vacancy creation and vacancy trapping, and further modulated by how the powder sinters into a dense ceramic. For engineers working on intermediate-temperature solid oxide fuel cells, the practical takeaway is that a modest 10 mole percent ceria addition, produced with tight chemical control during synthesis, can deliver higher conductivity at 700 degrees Celsius with the lowest activation energy in the series, bringing the community one step closer to fuel cells that run efficiently at temperatures their seals, stacks, and balance-of-plant components can actually tolerate.

The research also highlights the value of pairing synthesis innovation with multi-technique characterization. The water-free co-precipitation route in ethanol with triethylamine gave the team phase-pure fluorite powders across the entire compositional range, allowing the effect of cerium content to be isolated cleanly from synthesis artifacts. Combined with X-ray diffraction for structure, microscopy for microstructure, impedance spectroscopy for transport, XPS for oxidation states, and relaxation-time analysis for process deconvolution, the approach produced a coherent, mechanistically grounded picture of a material system that has been studied for decades yet still yields surprises. As solid oxide fuel cells edge toward commercial deployment for stationary power, hydrogen production, and even reversible operation as electrolysers, studies like this one remind the field that the path to better performance often runs not through exotic new materials, but through a sharper understanding of the defect physics hiding inside familiar ones.

Subject of Research: Ceria doping of yttria-stabilized zirconia electrolytes for solid oxide fuel cells

Article Title: Tailoring the structural and electrical properties of yttria-stabilized zirconia through ceria doping for SOFC

Article References: Chaudhary, K. J., Chaudhary, K. A., Khanna, S., Chaudhari, R. L., Chaudhari, V., Panchal, H. P., & Chaudhari, A. S. (2026). Tailoring the structural and electrical properties of yttria-stabilized zirconia through ceria doping for SOFC. Ionics. https://doi.org/10.1007/s11581-026-07485-0

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07485-0

Keywords: solid oxide fuel cells, yttria-stabilized zirconia, ceria doping, oxygen vacancies, ionic conductivity, electrochemical impedance spectroscopy, fluorite structure, defect chemistry, intermediate-temperature SOFC, co-precipitation synthesis, X-ray photoelectron spectroscopy, distribution of relaxation time

The material at the heart of the study is cesium dihydrogen phosphate, or CsH2PO4, a solid acid that has attracted sustained attention because of its behavior at intermediate temperatures. Solid acids occupy a curious middle ground between ordinary salts and liquid acids: their crystal lattices contain acidic protons that can hop between anion sites, and above a characteristic transition temperature the hydrogen-bond network reorganizes in a way that unlocks dramatically faster proton motion. For CsH2PO4, this superprotonic transition occurs at roughly 228 degrees Celsius, above which the material conducts protons efficiently enough to serve as the electrolyte in a fuel cell. The catch is that the same thermal regime brings problems. The compound dehydrates to cesium metaphosphate if the ambient humidity is not carefully controlled, and its mechanical and chemical stability at operating temperatures leaves much to be desired for real-world devices.

The strategy pursued by the research team belongs to a well-established but still rapidly evolving playbook in solid-state ionics: composite formation. Rather than trying to chemically dope the solid acid or replace it outright, the researchers dispersed zirconium pyrophosphate, ZrP2O7, into the CsH2PO4 matrix to form a family of composite electrolytes. Zirconium pyrophosphate is itself an interesting compound in this context. Metal pyrophosphates of the general formula MP2O7 have been shown to conduct protons at intermediate temperatures, particularly when their surfaces adsorb water or when acceptor dopants create oxygen vacancies that facilitate hydration. They are also structurally robust, thermally stable ceramics, which makes them attractive as a supporting phase for a solid acid that would otherwise soften and degrade.

The results reported for the composite labeled S2, the best-performing formulation in the series, are remarkable. At 320 degrees Celsius, the composite achieved a proton conductivity of 8.31 times ten to the minus two siemens per centimeter, a figure the authors state is roughly three to four orders of magnitude higher than that of pure CsH2PO4 under comparable conditions. To put that in perspective, a conductivity of nearly ten to the minus one siemens per centimeter places this composite firmly in the territory required for practical electrolyte membranes, where ohmic losses across the electrolyte layer must be minimized to keep fuel cell efficiency high. A three to four order of magnitude enhancement is not an incremental improvement; it is the difference between a laboratory curiosity and a material that can plausibly anchor a device.

Why does adding a second, nominally less conductive phase supercharge proton transport? The answer lies in the interfaces. In composite solid electrolytes, the boundary region between the two constituent phases hosts a distinctive microenvironment. Lattice strain, defect chemistry, and surface chemistry all conspire to create pathways with lower activation barriers for proton hopping. In the CsH2PO4-ZrP2O7 system, the pyrophosphate particles appear to stabilize the highly conductive cubic phase of the solid acid, effectively extending the temperature window in which fast proton conduction persists. The interfaces also disrupt the growth of large grains and alter the way the solid acid dehydrates, mitigating the degradation pathways that normally plague pure CsH2PO4 at operating temperatures. The authors note that the addition of ZrP2O7 enhanced both the conductivity and the stability of the solid acid, with the composites exhibiting property values that diverged substantially from those of the parent compound.

Characterizing such composites requires a battery of techniques spanning electrochemistry, crystallography, and thermal analysis, and the study evaluated the materials across all three domains. Electrochemical impedance spectroscopy, the workhorse method for measuring ionic conductivity in solids, separates the contributions of bulk transport, grain boundary transport, and electrode polarization by probing how the material resists alternating currents of different frequencies. Structural probes reveal whether the pyrophosphate retains its identity within the composite or reacts with the solid acid, and whether the superprotonic phase transition of CsH2PO4 shifts or broadens in the presence of the second phase. Thermal analysis, meanwhile, tracks the phase transitions, dehydration behavior, and overall stability of the composites as they are heated, information that is essential for judging whether a material can survive the thermal cycling of a real fuel cell stack.

The broader significance of this work sits within a decades-long effort to make intermediate-temperature fuel cells practical. Operating a fuel cell between roughly 200 and 400 degrees Celsius offers real advantages: electrode kinetics for both hydrogen oxidation and oxygen reduction speed up substantially, the need for expensive platinum catalyst loadings decreases, and waste heat becomes useful enough to recover in combined heat and power applications. Polymer electrolyte membrane fuel cells cannot operate in this range because their membranes dry out, while conventional oxide-based ceramic fuel cells require temperatures approaching 800 degrees Celsius or more, which stresses seals, interconnects, and balance-of-plant components. Solid acid electrolytes and pyrophosphate-based ceramics are among the leading candidates to fill this intermediate window, and composite approaches that combine the two families represent a particularly promising synthesis of their respective strengths.

The literature surrounding CsH2PO4 composites shows how active this field has become. Researchers have previously blended the solid acid with oxides such as silica and zirconia, with other phosphates such as neodymium phosphate, and even with metal-organic framework nanoparticles, in each case seeking to stabilize the superprotonic phase and suppress dehydration. Work on metal pyrophosphates, including zirconium pyrophosphate doped with trivalent cations such as indium, has demonstrated that these ceramics can serve as proton conductors in their own right at intermediate temperatures, and they have even been explored as cathode materials in single-chamber microbial fuel cells for bioenergy production. The present study builds on this foundation, and the authors’ own earlier publications on CsH2PO4 composites with sodium dihydrogen phosphate and zirconia show a sustained research program aimed at systematically tuning the composite chemistry for fuel cell applications.

Several practical questions remain on the path from a promising laboratory measurement to a deployable electrolyte. Long-term durability under fuel cell operating conditions, including exposure to humid gas streams and repeated thermal cycling, will need to be demonstrated over thousands of hours. The mechanical integrity of composite membranes at 320 degrees Celsius, where the solid acid component is mechanically softened even if chemically stabilized, must be engineered through careful control of particle loading and microstructure. Gas tightness is another perennial challenge for ceramic and composite electrolytes, since fuel cells require the anode and cathode gas streams to remain separated. Nevertheless, conductivity values approaching ten to the minus one siemens per centimeter at intermediate temperatures give material designers real headroom to address these engineering constraints without sacrificing electrochemical performance.

The study also underscores a broader lesson in materials science: sometimes the most powerful way to improve a material is not to perfect it in isolation but to pair it with a partner whose interface chemistry unlocks behavior neither phase exhibits alone. Heterogeneous additives, as the authors describe them, have now shown that they can serve as effective components of composite solid electrolytes across multiple systems. As the hydrogen economy matures and the demand for efficient electrochemical energy conversion grows, composite proton conductors built from inexpensive, abundant phosphate chemistry may prove to be quiet workhorses of the transition, converting hydrogen and oxygen into electricity at temperatures gentle enough for ordinary engineering materials yet hot enough for fast, efficient electrode reactions. The work by Kumar, Veer, Singh, and Katiyar adds a compelling data point to that trajectory, demonstrating that a carefully constructed solid acid pyrophosphate composite can deliver conductivity gains measured in orders of magnitude, along with the structural and thermal resilience that practical fuel cell operation demands.

Subject of Research: Proton-conducting CsH2PO4-ZrP2O7 composite electrolytes for intermediate-temperature fuel cells

Article Title: Enhancing electrochemical, structural, and thermal performance of a new protonic conductive electrolyte

Article References: Enhancing electrochemical, structural, and thermal performance of a new protonic conductive electrolyte. (n.d.). https://doi.org/10.1007/s11581-026-07462-7

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07462-7

Keywords: proton conductivity, solid acid electrolyte, cesium dihydrogen phosphate, zirconium pyrophosphate, composite electrolyte, fuel cells, intermediate temperature, ionic conduction, electrochemical impedance spectroscopy, solid state ionics, pyrophosphate, electrolyte stability

The molecule, named N1,N4-bis((1H-benzo[d]imidazol-2-yl)methyl)cyclohexane-1,4-dicarboxamide, or BCHDA, was assembled by coupling 2-aminomethylbenzimidazole with cyclohexane-1,4-dicarboxylic acid in pyridine, using triphenyl phosphite as a dehydrating agent. The reaction produced a white solid in 44 percent yield with a melting point of 310 degrees Celsius. Its structure was confirmed through elemental analysis, FT-IR and UV-visible spectroscopy, proton and carbon-13 NMR, high-resolution mass spectrometry and single-crystal X-ray diffraction. The proton NMR revealed a roughly 7:1 mixture of cis and trans isomers around the central cyclohexane ring, a detail the team tracked carefully through the characteristic resonances of the axial and equatorial hydrogens.

What makes BCHDA special is its architecture. Where most previously studied benzimidazole inhibitors carry a single fused aromatic ring, BCHDA carries two, linked through amide bridges to a cyclohexane core. Each benzimidazole unit is rich in electron-donating nitrogen atoms, and the amide groups add further oxygen and nitrogen donor sites. In principle, this gives the molecule multiple anchoring points for bonding to an iron surface, along with an extended conjugated pi-electron system capable of sharing electron density with vacant metal d-orbitals. The researchers set out to test whether this dual-ring design translates into superior protection.

The electrochemical evidence was unambiguous. Using potentiodynamic polarization in 0.5 molar sulfuric acid, the team found that adding BCHDA suppressed both the anodic dissolution of iron and the cathodic evolution of hydrogen gas. The corrosion potential shifted by less than 85 millivolts relative to the blank solution, the accepted signature of a mixed-type inhibitor acting on both halves of the corrosion reaction. At the highest concentration tested, 10 to the minus 3 molar, and at 298 kelvin, the corrosion current density fell so dramatically that the calculated inhibition efficiency reached 99.13 percent. Efficiency rose with concentration but declined with temperature, dropping to 92.80 percent at 328 kelvin at the same dose, a pattern consistent with partial desorption of the inhibitor film as thermal agitation increases.

Electrochemical impedance spectroscopy told a matching story. The Nyquist plots showed depressed capacitive semicircles whose diameters grew steadily with inhibitor concentration, reflecting a rising charge-transfer resistance at the metal-electrolyte interface. The data fitted well to a two-time-constant equivalent circuit, with one relaxation process assigned to the dielectric response of the adsorbed inhibitor film and the other to charge transfer across the double layer. From the impedance measurements the team derived a maximum inhibition efficiency of 94.32 percent at 10 to the minus 3 molar and 298 kelvin. The small discrepancy with the Tafel-derived figure arises because the two techniques probe different aspects of the corrosion process, one under finite overpotential and the other near open circuit, yet both showed the same concentration-dependent trend.

Adsorption analysis showed that the surface coverage data followed the Langmuir isotherm almost perfectly, indicating monolayer adsorption on energetically equivalent sites with negligible interaction between adsorbed molecules. The standard free energy of adsorption came out near minus 40 kilojoules per mole, right at the boundary between physical and chemical adsorption, while the adsorption enthalpy of minus 72.23 kilojoules per mole pointed clearly toward dominant chemisorption. The negative adsorption entropy indicated that the molecules become more ordered as they assemble into a protective layer at the metal-solution interface. Arrhenius analysis added further support, with activation energies for the inhibited systems exceeding those of the blank acid, confirming that the adsorbed film acts as a genuine kinetic barrier.

Direct imaging sealed the case. Scanning electron micrographs of polished steel showed a smooth surface marked only by polishing lines. After 24 hours in uninhibited sulfuric acid the surface was ravaged by cracks, pits and irregular corrosion products. In acid containing BCHDA the damage was dramatically reduced, with the 10 to the minus 3 molar sample retaining the smoothest morphology. Energy-dispersive X-ray analysis quantified the difference: iron content on the surface fell from 98.73 percent on polished steel to 56.35 percent after uninhibited acid exposure, but recovered to 71.52 percent in the presence of the inhibitor, while oxygen from oxide corrosion products dropped from nearly 40 percent to about 13 percent. Crucially, carbon and nitrogen signals appeared on the protected surfaces, direct fingerprints of adsorbed BCHDA molecules.

To understand why the molecule works so well, the team turned to density functional theory at the B3LYP/6-311+G(d,p) level, computing descriptors for both the neutral molecule and its protonated form, which predominates in sulfuric acid. The neutral species showed a HOMO energy of minus 6.09 electron-volts, a small frontier orbital gap of 1.74 electron-volts and a high electrophilicity index, all markers of a molecule well suited to donating and accepting electron density at a metal surface. Protonation widened the gap to 3.06 electron-volts and reduced the electron-donating capacity, yet the protonated form remained strongly surface-active. Natural bond orbital analysis revealed powerful intramolecular charge-transfer interactions, including a sigma-to-lone-pair stabilization of 43.04 kilocalories per mole in the neutral molecule and a pi-to-pi-star delocalization of 45.23 kilocalories per mole in the protonated species, confirming that the conjugated framework stays electronically robust under acidic conditions.

Molecular dynamics simulations on a four-layer iron (110) slab in aqueous sulfuric acid provided the final molecular-scale picture. The neutral BCHDA molecule bound to the surface with an interaction energy of minus 185 kilocalories per mole, lying nearly parallel to the metal to maximize contact between its pi-system and the iron atoms. The protonated form, though slightly weaker at minus 160 kilocalories per mole, still adsorbed spontaneously through a synergistic combination of electrostatic attraction to the sulfate-charged surface and residual donor-acceptor bonding through unprotonated nitrogen sites. Together, the experiments and simulations reveal a dual-mode mechanism: rapid electrostatic coverage by protonated molecules followed by durable chemisorption of neutral ones through nitrogen and oxygen lone pairs and aromatic pi-electrons. The authors argue that this integrated experimental-theoretical strategy offers a blueprint for rationally designing the next generation of corrosion inhibitors, positioning bis-benzimidazole derivatives as promising candidates for protecting steel in some of the harshest acidic environments industry can produce.

Subject of Research: Corrosion inhibition of mild steel in sulfuric acid by a bis-benzimidazole diamide derivative

Article Title: Experimental and computational studies on the corrosion inhibition of Bisbenzimidazole diamide derivative on mild steel in acidic media

Article References: Kumar, A., Jain, R., Kumar, S., Sanyukta, Shabnam, Vashisht, H., Baxi, S., Mahiya, K., Mathias, G. E., Anadebe, V. C., Olasunkanmi, L. O., & Ebenso, E. E. (2026). Experimental and computational studies on the corrosion inhibition of Bisbenzimidazole diamide derivative on mild steel in acidic media. Discover Electrochemistry, 3(1), Article 86. https://doi.org/10.1007/s44373-026-00175-6

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00175-6

Keywords: corrosion inhibition, mild steel, benzimidazole, sulfuric acid, electrochemical impedance spectroscopy, potentiodynamic polarization, density functional theory, molecular dynamics, Langmuir isotherm, chemisorption, SEM-EDX, protective film

The choice of phytagel as the polymer host is central to the design. Phytagel, a gelling agent commonly used in plant biology laboratories, forms stable hydrogel networks through polysaccharide chains that can coordinate metal ions and host dissolved salts. In an electrolyte, the polymer matrix must do two things at once: provide mechanical integrity so the electrolyte can be handled as a free-standing sheet, and allow ions to move through it quickly enough to sustain high currents. Pure polymer electrolytes typically struggle with the second requirement, because ion transport in a solid polymer is slow compared with transport through a liquid. The Malaysian team addressed this by adding glycerol as a plasticizer, a small molecule that inserts itself between polymer chains, loosening the network and creating more pathways for potassium ions to hop through the material.

The more intriguing ingredient, however, is MIL-101(Fe), a porous iron-based metal-organic framework. Metal-organic frameworks, or MOFs, are crystalline lattices in which metal nodes are linked by organic ligands into structures riddled with nanoscale pores. First described in the 1990s, MOFs have become famous for gas storage and separation, but in recent years researchers have increasingly explored them as ion conductors. The idea is elegant: the ordered pores of a MOF can act as ion highways, while the framework’s metal nodes and ligand functional groups can interact with dissolved salt ions, helping to separate them from their counterions and speed their migration. In this study, the MIL-101(Fe) particles were dispersed throughout the phytagel-glycerol-salt matrix, creating a composite in which the framework and the polymer work together rather than in isolation.

The experimental characterization relied on standard tools of electrolyte science. Fourier-transform infrared spectroscopy, or FTIR, revealed shifts in the vibrational bands of the phytagel backbone, indicating direct interactions between the polymer’s functional groups and the MOF surface as well as the dissolved potassium and chloride ions. X-ray diffraction, or XRD, was used to track the degree of crystallinity and amorphous character in the films, since amorphous regions in a polymer generally favor ion mobility while excessive crystallinity blocks it. Electrochemical impedance spectroscopy then quantified how readily ions moved through each formulation. The team compared pristine MOF-containing films, films with MOF and salt, and the complete four-component system, and found that the full composite outperformed both simpler versions. The polymer-MOF interaction, they conclude, is what unlocks the highest conductivity, rather than any single ingredient acting alone.

To demonstrate that the material can function in a real device, the researchers assembled a two-electrode coin cell using the KCl/MIL-101(Fe)/phytagel/glycerol electrolyte. After 1000 charge-discharge cycles, the cell retained a specific capacitance of approximately 80 farads per gram, delivered an energy density of about 0.8 watt-hours per kilogram, and sustained a power density of roughly 22 watts per kilogram, all at room temperature. Perhaps most notably, the coulombic efficiency, a measure of how much charge put into the cell comes back out, reached about 98 percent. High coulombic efficiency over many cycles is a key indicator that an electrolyte is electrochemically stable and that parasitic side reactions are minimal, which is essential for any energy storage device intended to last thousands of cycles.

The performance numbers, while modest compared with the best liquid-electrolyte supercapacitors, are significant for a fully solid system. Energy density and power density trade off against each other in any storage device, a relationship often visualized in Ragone plots, and supercapacitors sit firmly on the high-power, lower-energy side of that landscape. What the Malaysian results suggest is that a solid electrolyte can be engineered to sit comfortably within that regime without sacrificing safety or mechanical robustness. Because the electrolyte is a self-supporting sheet, it eliminates the need for separators and liquid containment, simplifying device architecture and opening the door to flexible and wearable formats where leakage would be catastrophic.

The authors propose a mechanistic picture for why the MOF helps so much, drawing on the concepts of through-bond and through-space ion transport. In through-bond pathways, ions move by hopping between coordinating sites along the framework’s metal nodes and ligands, essentially following a molecular ladder built into the crystal. In through-space pathways, ions travel through the open pores and channels of the framework, assisted by the solvent-like environment that glycerol provides inside those channels. Both mechanisms have been supported by prior work on MOF-based electrolytes, including studies of biomimetic ionic channels in lithium-ion systems and cross-linked MOF chains that afford continuous ion transport in solid batteries. In the phytagel composite, the framework appears to act as a dispersed network of ion-conducting domains embedded in the polymer, multiplying the available transport routes.

The broader context makes the work timely. Solid-state electrolytes are one of the most active frontiers in energy storage research, driven by the safety limitations of flammable liquid electrolytes in batteries and the packaging constraints of conventional supercapacitors. Composite solid polymer electrolytes, which blend a polymer host with inorganic or framework fillers, have emerged as a pragmatic middle path: they combine the processability and flexibility of polymers with the conductivity and stability of inorganic phases. Iron-based MOFs such as MIL-101(Fe) are particularly attractive fillers because iron is abundant, inexpensive, and relatively benign, in contrast to cobalt or rare-earth alternatives. The same material family has already been studied as an electrode material in lithium batteries and as a supercapacitor electrode in its own right, so integrating it into the electrolyte side of a device represents a natural extension of an established chemistry.

There remain hurdles between a laboratory coin cell and commercial devices. The energy density reported here is far below what lithium-ion batteries achieve, so supercapacitors built this way would serve applications where bursts of power matter more than total stored energy, such as regenerative braking, grid frequency regulation, and backup power for portable electronics. Cycle life beyond 1000 cycles, performance at elevated temperatures, and compatibility with high-voltage electrode materials all need further study. The authors also note that data supporting the study are available from the corresponding author upon reasonable request, and the work was supported by Universiti Malaya research funding. Still, the demonstration that a humble laboratory gelling agent can be married to a designer porous framework to produce a robust, highly conductive solid electrolyte is a reminder that breakthroughs in energy storage often come from unexpected combinations of everyday materials and precision-engineered ones.

For the field of solid-state supercapacitors, the phytagel-MOF composite adds a new and unusually sustainable entry to the palette of available electrolytes. Biopolymer hosts reduce reliance on petrochemical feedstocks, potassium chloride is cheap and non-toxic, and glycerol is a byproduct of biodiesel production. If subsequent work can push the conductivity higher, extend cycle life, and scale the sheet-casting process to larger areas, the humble conducting sheet described in Ionics could find its way into the flexible electronics and renewable energy systems where safe, fast, and durable energy storage is most urgently needed.

Subject of Research: Composite solid polymer electrolytes based on phytagel and the iron-based metal-organic framework MIL-101(Fe) for supercapacitor applications

Article Title: Phytagel-doped MIL-101(Fe) composite conducting sheets for supercapacitor applications

Article References: Abd Razak, N., Majid, S. R., & Abdul Halim, S. N. (2026). Phytagel-doped MIL-101(Fe) composite conducting sheets for supercapacitor applications. Ionics. https://doi.org/10.1007/s11581-026-07482-3

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07482-3

Keywords: metal-organic framework, MIL-101(Fe), phytagel, composite solid polymer electrolyte, supercapacitor, ionic conductivity, glycerol plasticizer, potassium chloride, energy storage, solid-state electrolyte, biopolymer, electrochemical impedance spectroscopy

The central component of any solid-state battery is the electrolyte, the medium through which charge-carrying ions shuttle between electrodes while electrons are forced around the external circuit. Liquid electrolytes dominate today’s commercial cells, but they bring well-documented problems: flammability, leakage, volatility, and complicated packaging. Solid polymer electrolytes promise a way around these hazards, yet many of the synthetic polymers used to make them, such as poly(vinyl alcohol) and polyacrylonitrile, are derived from petrochemicals and resist degradation. Biopolymer electrolytes offer an alternative route. Natural polysaccharides and plant-derived materials are renewable, inexpensive, and rich in oxygen-containing functional groups that can host mobile ions. Over the past decade, research groups have explored tamarind seed polysaccharide, iota-carrageenan, pectin, gellan gum, cellulose acetate, sodium alginate, agar, and even Moringa oleifera seeds as ion-conducting hosts. The new study adds a familiar garden herb to that growing roster.

The team’s method was deliberately simple. Leaves of Plectranthus amboinicus were processed and blended with ammonium nitrate, NH4NO3, in varying proportions using the solution casting technique, a low-energy process in which a dissolved mixture is poured into a mold and left to dry into a free-standing film. The resulting bio-membranes were then interrogated with a battery of characterization techniques: X-ray diffraction to probe their internal structure, differential scanning calorimetry and thermogravimetric analysis to assess thermal behavior, electrochemical impedance spectroscopy to measure ionic conductivity, linear sweep voltammetry to test electrochemical stability, and ion transport number measurements to confirm which charge carriers were actually moving.

The structural findings explain much of the material’s performance. X-ray diffraction revealed that the films were predominantly amorphous, meaning their molecular chains lacked the long-range ordered packing of a crystal. This matters because ion transport in polymer electrolytes proceeds through flexible, disordered regions: amorphous chains segment and rearrange with thermal motion, opening transient pathways through which small ions can hop. The most amorphous membrane, labeled PALN3, contained 1 gram of Plectranthus amboinicus leaf material complexed with 0.8 percent molecular weight of ammonium nitrate. In crystalline regions, by contrast, polymer chains are locked in place and ions are trapped or blocked. The amorphous character of the best composition thus set the stage for the conductivity results that followed.

And those results were striking. Electrochemical impedance spectroscopy showed that the PALN3 membrane achieved an ionic conductivity of 1.18 times ten to the minus two siemens per centimeter, a figure that places it among the highest values reported for biopolymer electrolyte systems. For context, many undoped biopolymer membranes conduct at rates six or more orders of magnitude lower. The ammonium nitrate salt is the key additive: when ammonium ions dissociate from nitrate counterions within the leaf-derived polymer matrix, they provide mobile proton carriers, while the salt disrupts chain packing and further suppresses crystallinity. The researchers also computed transport parameters using an equivalent circuit formalism developed by A. K. Arof, a widely used analytical approach that separates bulk, grain boundary, and electrode contributions from the impedance response.

Proton conduction itself is a fascinating and unusual branch of ion transport. Unlike lithium or sodium ions, which drag a solvation shell through the electrolyte in a vehicle-like mechanism, protons are far too small to exist freely in a condensed medium. Instead, they typically migrate through hydrogen-bonded networks via the Grotthuss mechanism, essentially relayed from one hydrogen-bonded site to the next, like a bucket brigade passing water along a line. Plant-derived polymers, dense with hydroxyl, ether, and carbonyl groups, are naturally rich in hydrogen-bonding sites, which is precisely why they make such effective proton hosts. Recent work in the literature, including studies published in Communications Chemistry, has focused on directly observing this proton transfer process, and the field increasingly recognizes biological and bioinspired materials as ideal scaffolds for engineering Grotthuss-type conduction.

Before a membrane can serve in a device, it must survive the electrochemical environment. The team’s thermogravimetric analysis established the material’s thermal stability window, while linear sweep voltammetry confirmed that the electrolyte remains electrochemically stable across the operating range of the cell. Ion transport number measurements verified that protons, rather than electrons or other ionic species, dominate the conduction, a crucial check because electronic leakage would cause self-discharge and render the membrane useless as a battery separator. With these criteria satisfied, the researchers selected the highest-conductivity PALN3 membrane as the electrolyte for fabricating a primary proton-conducting battery.

The assembled cell delivered an open-circuit voltage of 1.64 volts, a respectable figure for a proton battery built from a plant-based electrolyte, comparable to the nominal voltages of many conventional primary chemistries. The team then examined the battery under different load conditions to assess how the voltage and current output held up as the cell was asked to do real work. Load testing is where laboratory curiosities either prove their mettle or fall apart, since internal resistance and mass transport limitations typically cause voltage to sag under current draw. While the study reports the device as a primary, non-rechargeable cell, the demonstration completes the full chain from raw leaf to functioning electrochemical device, a pipeline that earlier work from the same research community has applied to Centella asiatica, Peltophorum pterocarpum, and Ocimum sanctus membranes.

The appeal of this approach extends beyond novelty. Plectranthus amboinicus is fast-growing, widely cultivated, and requires no exotic processing infrastructure, and ammonium nitrate is an inexpensive commodity chemical. Solution casting needs no high temperatures or vacuum systems, making the entire fabrication route accessible and low-carbon. At end of life, a biodegradable membrane avoids the persistent waste problems associated with synthetic polymer separators. None of this means herb-based proton batteries will displace lithium-ion in smartphones tomorrow; primary cells, energy density, cycle behavior, and scale-up all remain open questions, and the published abstract does not report long-term cycling data. But as a proof of concept, the work is compelling. It suggests that the next generation of safe, sustainable solid-state energy storage might be grown in a garden rather than refined from a mine, and that the humble oregano pot on a windowsill could one day share a lineage with the battery in your pocket.

Subject of Research: A plant-derived biopolymer electrolyte from Plectranthus amboinicus leaves and ammonium nitrate for proton-conducting solid-state batteries

Article Title: Development of biomaterial plectranthus amboinicus for proton conducting battery

Article References: Kowsalya, S., Prameela, P., Selvasekarapandian, S., & Devi, S. K. (2026). Development of biomaterial plectranthus amboinicus for proton conducting battery. Ionics. https://doi.org/10.1007/s11581-026-07569-x

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07569-x

Keywords: Plectranthus amboinicus, biopolymer electrolyte, proton conduction, ammonium nitrate, solid-state battery, solution casting, ionic conductivity, X-ray diffraction, electrochemical impedance spectroscopy, Grotthuss mechanism, primary battery, sustainable energy materials

Electrochemical impedance spectroscopy, or EIS, works by applying a small sinusoidal voltage or current perturbation across a range of frequencies and measuring the cell’s response. At high frequencies, the technique reveals the resistance that ions and electrons encounter as they move through electrolytes and across interfaces. At low frequencies, it exposes the slower processes of diffusion, the way lithium ions wander through electrode materials to find their storage sites. By fitting the resulting spectra to equivalent circuit models, researchers can separate these contributions and assign numerical values to them. In this study, the two most telling parameters were the charge transfer resistance, denoted R-CT, which describes the energetic barrier that lithium ions must overcome to cross the electrode-electrolyte interface, and the Warburg impedance, W, which captures the resistance to solid-state diffusion deep within the electrodes.

The team systematically varied the state of charge, or SOC, of polymer lithium-ion cells and recorded impedance spectra at each point, paying particular attention to what happens when the cells are driven into the over-discharge regime. The results revealed a striking asymmetry between the high and low ends of the voltage window. In the high state-of-charge region, spanning voltages from 4.2 volts down to 3.7 volts, the charge transfer resistance increased steadily while the Warburg impedance remained relatively steady. This makes physical sense: when a cathode is nearly full of lithium or an anode is nearly empty, the interfacial kinetics change, but the diffusion pathways through the bulk electrode material remain largely intact.

The picture changed dramatically in the low state-of-charge and over-discharge zone, covering voltages from 3.6 volts down to 2.0 volts. Here the researchers observed a significant rise in the Warburg impedance alongside a drop in the charge transfer resistance. This combination signals that the dominant limitation shifts from the interface to the bulk: lithium ions find it increasingly difficult to diffuse through the electrode material, while the interfacial reaction kinetics are paradoxically altered in a way that lowers the apparent charge transfer barrier. The authors interpret this as evidence of enhanced diffusion restrictions and altered interfacial kinetics, a signature that over discharge reshapes the interior landscape of the cell rather than merely fouling its surfaces.

One of the most important findings concerns the subtlety of the damage. When the researchers compared spectra taken at equivalent voltages and equivalent cycle numbers, they found that over discharge does not produce dramatic spectral distortion. Instead, it induces progressive shifts in the interfacial resistance and in the low-frequency response of the cell. This is a crucial insight for battery diagnostics, because it means that a catastrophic-looking failure may be preceded by gradual, measurable changes that only careful impedance monitoring would catch. A battery management system that tracks these parameters over time could, in principle, flag a cell that has been over-discharged long before its capacity loss becomes obvious to the user.

The study also examined how these impedance parameters evolve with repeated cycling. Both the charge transfer resistance and the Warburg impedance increased gradually as the cells were cycled, with the tenth cycle exhibiting significantly higher values than the first. This progressive growth suggests cumulative electrode deterioration and a steady loss of ionic transport efficiency. In practical terms, each abuse event, each excursion into the over-discharge zone, leaves a residue of damage that accumulates. The electrodes lose their ability to shuttle lithium ions efficiently, and the battery’s internal resistance climbs, which in turn increases heat generation, reduces power output, and accelerates further degradation in a self-reinforcing loop.

The implications for battery management systems are significant. Modern BMS technology increasingly relies on impedance-based methods to estimate the state of charge and state of health of cells, and a rich body of literature has developed around using EIS for these purposes. Previous studies have shown that impedance measurements can support state-of-charge estimation even for aging batteries, and machine learning approaches have been layered on top of impedance data to improve prediction accuracy. However, most of this work assumes the battery operates within its normal voltage window. The Daegu University study adds a missing piece: a quantitative description of how the key impedance parameters behave when that assumption is violated, which is exactly the situation that occurs in real-world abuse scenarios such as deep discharge during vehicle breakdowns, faulty electronics, or user error.

The findings also connect to a broader research effort on over-discharge failure mechanisms. Earlier work on commercial lithium iron phosphate cells showed that over discharge causes structural and chemical changes in electrodes, including copper dissolution from the anode current collector at extreme depths of discharge, which can lead to internal short circuits. Other studies have documented effects on performance and thermal stability. What distinguishes the new study is its focus on polymer lithium-ion batteries, a format favored for its flexibility and safety, and its systematic separation of the impedance response into interfacial and diffusional components across the full discharge range, including the abusive zone below the normal cutoff voltage.

For consumers, the research underscores a familiar message with new precision: the damage from draining a battery too far is real, measurable, and cumulative. For engineers, it provides a diagnostic roadmap. Because the impedance changes induced by over discharge are systematic rather than chaotic, they can be incorporated into the models that battery management systems use to monitor cell health. A vehicle or device that periodically measures its cells’ impedance could detect the characteristic rise in Warburg impedance and the shifting interfacial resistance that betray a history of deep discharge, then adjust charging strategies or flag the cell for inspection. The authors emphasize that impedance monitoring of this kind is important for early degradation detection and battery management in polymer lithium-ion batteries.

As the world electrifies transportation and deploys ever-larger stationary storage systems, the economics of battery longevity become staggering in scale. Extending the useful life of a battery pack by even a few percentage points translates into enormous savings of cost, raw materials, and environmental impact. Studies like this one, which translate the invisible electrochemistry of degradation into measurable electrical signatures, are the foundation of that effort. The over-discharged battery, it turns out, does tell the story of its abuse; it simply tells it in the language of impedance, at frequencies and magnitudes that only careful spectroscopy can hear. Learning to listen, the Daegu University work suggests, may be one of the most practical steps toward smarter, longer-lived, and safer energy storage.

Subject of Research: Electrochemical impedance analysis of polymer lithium-ion batteries under over-discharge conditions

Article Title: Impedance analysis of polymer lithium-ion batteries under over discharge

Article References: Subedi, M., & Jeong, H. K. (2026). Impedance analysis of polymer lithium-ion batteries under over discharge. Ionics. https://doi.org/10.1007/s11581-026-07501-3

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07501-3

Keywords: lithium-ion battery, over discharge, electrochemical impedance spectroscopy, charge transfer resistance, Warburg impedance, state of charge, battery degradation, polymer battery, battery management system, ionic transport, electrode deterioration, energy storage

Researchers led by Siti Nor Hafiza Mohd Yusoff of Universiti Teknologi MARA in Malaysia systematically examined what actually happens when rutile titanium dioxide nanoparticles, with a nominal size below 100 nanometers, are dispersed into PEO and into PEO loaded with lithium perchlorate, one of the classic polymer-salt electrolyte systems. Their findings, published in Discover Industrial Chemistry and Materials, are striking in their consistency: across every composition tested, the nanofiller behaved as an essentially inert passenger. It did not change the glass transition temperature, the heat capacity step, the crystallinity, the melting behavior, the spherulitic morphology, or the ionic conductivity of the host matrix. The particles simply sat there, largely untouched by and un-touching of the polymer around them.

The team prepared free-standing films by solution casting, dissolving PEO, lithium perchlorate, and titanium dioxide in acetonitrile, stirring for 24 hours at 50 degrees Celsius, and then homogenizing the mixture with an Ultra-Turrax at 5000 rpm to minimize agglomeration. The salt concentration was deliberately fixed at a mass fraction of 0.107, a composition thoroughly characterized in the group’s earlier work, so that any observed changes could be attributed cleanly to the nanofiller rather than to shifting polymer-salt interactions. Filler mass fractions ranged from zero up to 0.043 in the ternary system, and every film was carefully dried and thermally annealed to erase any history from the preparation process.

Differential scanning calorimetry provided the first line of evidence. The glass transition temperature of the PEO-lithium perchlorate system dropped from 243 K to roughly 235 K upon the very first addition of titanium dioxide, a shift the authors attribute to a slight weakening of ion-dipole interactions between the polymer and the salt. But beyond that initial step, further increases in filler content produced no significant change whatsoever in the glass transition, the change in heat capacity at the transition, the apparent melting temperature, or the degree of crystallinity, which was calculated against the reference enthalpy of 188.3 joules per gram for perfectly crystalline PEO. In a genuinely miscible system, adding a second component should depress the melting point and reshape the thermal signature of the host. Here, nothing of the sort occurred, a hallmark of phase separation and weak molecular interaction.

The heat capacity data carried particular weight. Because the glass transition reflects the configurational entropy and segmental freedom of amorphous polymer chains, a filler that actively modified the matrix would alter both the transition temperature and the magnitude of the heat capacity step. The researchers normalized their measured values to account for the amorphous fraction of PEO, subtracting the crystalline phase from the total polymer mass, and found the normalized values essentially flat across all filler loadings, with experimental errors below three percent. The mobile amorphous fraction of the polymer, in other words, was preserved intact. The titanium dioxide neither restricted chain motion nor unlocked additional mobility, suggesting it never meaningfully penetrated or perturbed the amorphous regions where ion transport takes place.

Polarized optical microscopy told the same story visually. At room temperature, well below the melting point of PEO at about 65 degrees Celsius, the films displayed the familiar bright spherulitic crystals embedded in dark amorphous regions. Adding even a small amount of filler, at a mass fraction near 0.0089, coarsened the spherulites and increased the apparent nucleation sites, yet the fibrillose architecture of the spherulites remained largely undisturbed. At higher loadings, around 0.043, dark agglomerated patches of titanium dioxide appeared in the matrix, but these micro-scale clusters sat within the polymer without disrupting its crystalline superstructure. The morphology confirmed what the calorimetry implied: an immiscible, phase-separated composite in which the filler and the polymer coexist without meaningful dialogue.

Electrochemical impedance spectroscopy, measured at 25 degrees Celsius from 50 hertz to 1 megahertz with stainless steel blocking electrodes, completed the picture. The Nyquist plots showed the characteristic depressed semicircle and low-frequency spike of a polymer electrolyte dominated by electrode polarization, and equivalent circuit fitting extracted bulk resistance, bulk capacitance, double-layer capacitance, and Warburg impedance elements. The bulk resistance shifted only marginally with increasing filler content, producing conductivities in the same order of magnitude, from 10⁻⁶ to 10⁻⁷ S cm⁻¹, as the filler-free PEO-lithium perchlorate baseline. Bode analysis of the characteristic frequencies of minimum and maximum impedance, along with the crossover frequency marking the onset of dipole percolation, revealed relaxation behavior that stayed within experimental error regardless of loading, reinforcing the conclusion that the nanofiller left the ion transport pathways untouched.

The dielectric analysis added mechanistic depth. The real part of the complex permittivity, which reflects energy storage through dipole polarization, rose steeply at low frequencies due to interfacial polarization at the electrodes, but the addition of titanium dioxide did not promote this polarization. At high frequencies near 10⁶ hertz, the dielectric constant settled to values that showed insignificant variation across all filler fractions. The exponent extracted from the power-law decay of dielectric loss, which distinguishes ideal Debye relaxation with a single time constant from the distributed relaxation typical of heterogeneous systems, remained constant within error. The loss tangent peaks diminished slightly in magnitude and shifted marginally to lower frequencies as filler content increased, indicating a modest reduction in the number of relaxing dipoles, but the overall relaxation landscape was essentially unchanged. Charge transport, the authors conclude, is governed by the molecular interactions among the charged entities of the PEO-lithium perchlorate complex itself, not by any polymer-filler interfacial chemistry.

Why does this matter, and why does it contradict so much of the published literature? Many studies have reported conductivity enhancements from titanium dioxide in PEO electrolytes, typically attributed to Lewis acid-base interactions between surface groups on the nanoparticles and the polymer or salt, which reduce crystallinity and promote ion dissociation. But those outcomes depend critically on nanoparticle surface chemistry, loading, salt type and concentration, polymer molecular weight, preparation route, and dispersion quality. In this study, untreated rutile particles with weak interfacial interaction and a tendency to agglomerate offered little effective surface area for such chemistry to occur. The result is a sobering reference point: nanofiller addition does not inherently guarantee improved electrolyte performance, and the field’s enthusiasm for ceramic additives must be tempered by a clear-eyed assessment of whether genuine polymer-filler interactions actually form.

The practical message for battery designers is twofold. First, establishing strong, deliberate polymer-nanofiller interactions, through surface functionalization or carefully matched chemistry, is essential if fillers are to do real work in solid polymer electrolytes; simply mixing in nanoparticles is not enough. Second, the combined DSC, microscopy, and impedance methodology demonstrated here offers a rigorous template for verifying whether a given filler is an active modifier or an inert bystander in any candidate electrolyte system. As solid-state batteries edge closer to commercial reality, distinguishing the fillers that genuinely enhance ion transport from those that merely add mass will be crucial for rational materials design. This study, by carefully documenting a case of near-perfect inertness, provides exactly the kind of negative result that helps the field calibrate its expectations and redirect its efforts toward interfaces that truly matter.

Subject of Research: The role of titanium dioxide nanofillers in PEO-lithium perchlorate solid polymer electrolytes

Article Title: Inertness of titanium dioxide nanofillers in polyethylene oxide and lithium perchlorate polymer electrolytes

Article References: Inertness of titanium dioxide nanofillers in polyethylene oxide and lithium perchlorate polymer electrolytes. (n.d.). https://doi.org/10.1007/s44508-026-00024-9

Image Credits: AI Generated

DOI: 10.1007/s44508-026-00024-9

Keywords: solid polymer electrolytes, poly(ethylene oxide), titanium dioxide, nanofillers, lithium perchlorate, ionic conductivity, differential scanning calorimetry, electrochemical impedance spectroscopy, dielectric relaxation, glass transition, crystallinity, lithium batteries