The appeal of pairing these two oxides lies in their complementary strengths. V2O5 is a classic pseudocapacitive material, storing charge through fast, surface-level redox reactions involving multiple vanadium oxidation states, and it is also an established catalyst platform for oxygen and hydrogen evolution. SnO2, by contrast, is chemically stable, inexpensive, and conducts electrons well, but on its own it is a poor charge-storage material. The researchers reasoned that anchoring SnO2 onto a V2O5 framework could combine vanadium’s redox richness with tin’s stability and conductivity, while the interface between the two phases would create new active sites and accelerate charge transfer.

Synthesis followed a straightforward hydrothermal route, in which precursor solutions were sealed in an autoclave and heated, allowing the two oxides to crystallize together into an integrated architecture. Electron microscopy and spectroscopy confirmed that SnO2 nanoparticles were successfully anchored onto the V2O5 framework, forming intimate Sn–O–V interfaces rather than loosely mixed powders. X-ray photoelectron spectroscopy verified the coexistence of Sn4+ and multiple vanadium oxidation states, evidence that the redox chemistry of the vanadium phase remained fully accessible in the composite.

As a supercapacitor electrode, the heterostructure delivered a high specific capacitance, substantially outperforming the individual oxides. The team attributes this to three effects working together: the pseudocapacitive redox reactions of V2O5, the improved electronic conductivity provided by SnO2, and the abundant interfacial active sites that shorten ion diffusion paths. Electrochemical impedance spectroscopy showed lower charge-transfer resistance in the composite than in either pristine oxide, consistent with faster electron movement across the Sn–O–V junctions.

The electrode also demonstrated good rate capability and cycling stability, retaining a large fraction of its capacitance at high current densities and over extended charge–discharge cycling. The researchers connect this durability to the mechanical and chemical robustness of the SnO2 component, which buffers the volume changes that vanadium oxides typically suffer during repeated redox reactions. In practical terms, that combination of high capacitance and stability is exactly what separates laboratory supercapacitors from devices that can survive thousands of real-world cycles.

The same material proved equally capable as a water-splitting catalyst. In alkaline electrolyte, the heterostructure required low overpotentials to drive both the hydrogen evolution reaction and the oxygen evolution reaction, with current densities comparable to or better than those of the constituent oxides. Tafel analysis indicated favorable reaction kinetics, and long-term electrolysis tests showed the catalyst maintaining its activity over extended operation. The team links the catalytic enhancement to the same interfacial engineering that boosts charge storage: the Sn–O–V junctions create electronic states that lower energy barriers for the elementary steps of hydrogen and oxygen production.

The dual functionality is more than a curiosity. Supercapacitors and electrolyzers both operate at the intersection of electricity and electrochemistry, and a material that serves both could simplify supply chains for renewable energy systems. The researchers suggest scenarios in which excess renewable electricity is stored in supercapacitors during the day and used to power water electrolysis when demand rises, with the same bifunctional material serving in both roles. Because both SnO2 and V2O5 are earth-abundant and inexpensive, the approach avoids the precious metals—platinum, iridium, ruthenium—that dominate current catalyst technology.

The study also contributes to a broader design principle emerging across energy materials research: heterostructure engineering, in which the interface between two phases becomes the active element. Similar strategies have been reported for SnO2 paired with carbon nitride, V2O5 combined with carbon dots, and ternary composites of SnO2, V2O5, and conductive carbons. The new work extends this principle by demonstrating that a single binary oxide heterostructure can simultaneously optimize charge storage and electrocatalysis, two functions usually pursued with different materials.

Challenges remain before the material reaches commercial devices. The researchers note that further optimization of the SnO2-to-V2O5 ratio, deeper understanding of the interfacial electronic structure, and evaluation in full-cell supercapacitor and electrolyzer configurations are needed. Scaling the hydrothermal synthesis to industrial quantities and verifying long-term stability under realistic operating conditions are also necessary steps. Nevertheless, the demonstration that one low-cost oxide pair can deliver both high capacitance and efficient water splitting marks a notable advance in the search for affordable, multifunctional energy materials.

The research, published in the Journal of Materials Science in 2025, was supported by the authors’ institutions. The full study, led by corresponding authors Asghar Nazir and Waheed Ahmad with coauthors including Sundararaj Muthukumaraswamy and Mahrukh Sadaf, is available in the journal. As renewable energy systems multiply worldwide, materials that can store electricity and produce hydrogen in the same breath may prove essential—and this bifunctional SnO2/V2O5 heterostructure offers a compelling, earth-abundant starting point.

Subject of Research: Development of bifunctional SnO2/V2O5 heterostructures for supercapacitor energy storage and water splitting application

Article Title: Development of bifunctional SnO2/V2O5 heterostructures for supercapacitor energy storage and water splitting application

Article References: Nazir, A., Rani, S., Sadaf, M., Jameel, S., & Ahmad, W. (2026). Development of bifunctional SnO2/V2O5 heterostructures for supercapacitor energy storage and water splitting application. Journal of Materials Science, 61(42), 33168-33188. https://doi.org/10.1007/s10853-026-13639-2

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13639-2

Keywords: Development, bifunctional, SnO2, V2O5, heterostructures, supercapacitor, energy, storage, water, splitting, application, scientific research

Zinc oxide occupies an unusual position among biomedical nanomaterials because its biological activity is dominated by a chemical process rather than a purely mechanical or structural one. Zinc oxide dissolves slowly in aqueous biological environments, releasing zinc ions into the surrounding medium. Zinc ions are essential nutrients at low concentrations, participating in hundreds of enzymatic reactions and signaling pathways, but they become cytotoxic at elevated intracellular levels, where they can disrupt mitochondrial function, generate oxidative stress, and activate apoptotic cascades. This concentration-dependent behavior explains the dual reputation of zinc oxide in the literature: it is antibacterial and can suppress cancer cell growth at sufficient doses, yet it can also harm healthy mammalian cells when the local ion concentration rises too high. The observation in this study that cell viability was compromised on zinc oxide nanowire surfaces, and that medium previously conditioned by exposure to those nanowires reproduced the toxic effect, is consistent with this ion-shedding mechanism. The conditioned-medium experiment is especially informative because it separates the effect of soluble zinc species from the effect of direct contact with the nanowire surface, and the finding that soluble compounds alone reduced filopodia length, spreading, and viability points strongly toward dissolved zinc as the principal mediator of toxicity.

The heterostructure concept adds a further layer of complexity. In materials science, heterostructures are valued because the interface between two dissimilar materials can produce properties that neither component exhibits alone, such as modified charge transfer, altered band alignment, or enhanced catalytic activity. In a biological context, however, the same interface effects that make heterostructures attractive for electronics and sensing can also change how the materials interact with their environment. A carbon nanotube network in contact with zinc oxide nanowires may alter the rate at which zinc ions are released, the local pH at the surface, or the way proteins from cell culture medium adsorb onto the surface. Protein adsorption, in turn, governs the initial attachment of cells, since cells do not bind directly to synthetic surfaces but rather to the protein layer that forms on them within seconds of exposure to serum. The finding that cells adhered to the heterostructures and extended filopodia across them suggests that the composite surface supported at least the earliest stages of cell attachment, even though longer-term viability suffered. This dissociation between initial adhesion and subsequent survival is a common pattern in biomaterials testing and underscores why multi-timepoint assessments are important when evaluating new surfaces.

Filopodia themselves merit attention as a readout of cellular response. These actin-rich membrane protrusions are among the first structures a cell deploys when exploring a new surface, and their length, density, and orientation reflect both the mechanical cues of the substrate and the health of the cell’s cytoskeletal machinery. On favorable surfaces, filopodia elongate, anchor to adhesion points, and mature into larger focal adhesions that support spreading and migration. On unfavorable or toxic surfaces, filopodia may retract, shorten, or fail to form altogether, as was observed when cells were exposed to zinc oxide nanowire-conditioned medium. Because filopodial behavior can be quantified from microscopy images, it serves as a sensitive early indicator of biocompatibility, often changing before conventional viability assays register a difference. The use of both fluorescence microscopy and scanning electron microscopy in this study allowed the researchers to capture complementary views: fluorescence imaging reveals the actin cytoskeleton and nuclear morphology of many cells across a sample, while electron microscopy resolves the fine detail of filopodia interacting with individual nanowires and nanotubes at the nanometer scale.

The choice of cell lines also shapes the interpretation of the findings. NIH 3T3 fibroblasts are a widely used normal-ish rodent cell line that serves as a standard benchmark for biocompatibility testing, representing the kind of connective tissue cell that would encounter an implanted material. U87 glioblastoma cells, by contrast, derive from an aggressive human brain tumor and are studied both as a model of cancer biology and as a target for anticancer strategies. The hypothesis that zinc oxide nanowires might selectively suppress cancerous cells while carbon nanotubes support healthy cell growth reflected a genuine aspiration in the nanomedicine field: to exploit differential vulnerabilities of tumor cells, such as their altered redox balance and membrane properties, to achieve selective toxicity. The observation that zinc oxide exposure harmed both cell types in this study tempers that aspiration but does not necessarily end it. Selectivity in nanotoxicology often depends on dose, exposure duration, particle size, surface functionalization, and the specific chemistry of the nanomaterial preparation, and a single unmodified nanowire formulation may simply fall outside the parameter range where selectivity emerges. Future work varying nanowire diameter, length, density, and surface coatings could probe whether a therapeutic window exists.

The chemical vapor deposition method used to synthesize these materials deserves comment as well. CVD is a high-temperature process in which gaseous precursors decompose on a catalyzed substrate to grow crystalline nanostructures directly in place. For carbon nanotubes, this yields structures with high crystallinity and well-defined electrical properties compared with solution-processed alternatives, and for zinc oxide nanowires it produces vertically aligned, single-crystal arrays whose wurtzite structure underlies their piezoelectric behavior. Growing the two materials sequentially on the same chip, so that nanowires rise from a carpet of nanotubes, produces an intimate interface that cannot be achieved by simply mixing dispersions. This pristine, substrate-grown architecture is what distinguishes the present work from earlier composite studies, and it also means that the biological results apply specifically to this geometry; powdered or polymer-embedded versions of the same materials may behave differently. The piezoelectric character of zinc oxide adds a speculative but intriguing dimension: because piezoelectric materials generate electrical charge under mechanical deformation, a zinc oxide nanowire surface could in principle transduce cellular contractile forces or external ultrasound into local electrical stimuli, which are known to influence cell behavior in tissues such as bone and nerve. Whether such effects operate at the interface studied here remains untested, but they represent one of the motivations for exploring zinc oxide nanostructures in biomedical contexts.

From a practical standpoint, the results suggest a division of labor for future scaffold design. Single-walled carbon nanotube surfaces, which supported pronounced cell spreading in this study, could serve as the conductive, mechanically robust backbone of a biomedical interface, providing the topography and electrical properties that promote adhesion and growth of desired cells. Zinc oxide nanowires, whose soluble products proved cytotoxic to both cell lines examined, might be better suited to applications where killing cells is the goal, such as antibacterial coatings or anticancer surfaces, or they might require mitigation strategies such as protective encapsulation, controlled-release coatings, or surface passivation that suppresses ion dissolution while preserving the nanowire architecture. Combining the two in a heterostructure remains attractive precisely because the interface could be engineered to tune ion release rates or to exploit charge transfer between the components, but the present findings make clear that the combination, as currently synthesized, inherits the toxicity of its zinc oxide component rather than being rescued by the carbon nanotube layer.

It is also worth noting the broader methodological lesson embedded in this work: the behavior of a nanomaterial in biological settings cannot be predicted from its bulk properties or from studies of related materials in different forms. The same zinc oxide that is benign in a sunscreen formulation can be harmful when presented as high-aspect-ratio nanowires on a surface, and the same carbon nanotubes that raise concerns as airborne powders can support cell growth when immobilized. Systematic studies that vary presentation format, dose, and cell type, as this study does by comparing three surface types against a silicon dioxide control and testing both contact and conditioned-medium effects, are the necessary foundation for any future translation of nanomaterial heterostructures into clinical devices. The data reported here, showing adhesion and filopodia extension across all tested nanostructures but viability loss on zinc oxide-containing surfaces, provide a clear and useful baseline for that ongoing effort, and they highlight both the promise and the unresolved toxicity questions that will shape the next generation of carbon nanotube and zinc oxide biomedical interfaces.

Subject of Research: Cell spreading and viability on single-walled carbon nanotube/zinc oxide nanowire heterostructures synthesized by chemical vapor deposition

Article Title: Cell spreading and viability on single-walled carbon nanotube/zinc oxide nanowire heterostructures synthesized by chemical vapor deposition

Article References: Luc, E., Aziz, B., Kim, Y., Lespasio, M., Jombo, P., Zustiak, S. P., & Kuljanishvili, I. (2024). Cell spreading and viability on single-walled carbon nanotube/zinc oxide nanowire heterostructures synthesized by chemical vapor deposition. Frontiers in Carbon, 3, Article 1400664. https://doi.org/10.3389/frcrb.2024.1400664

Image Credits: AI Generated

DOI: 10.3389/frcrb.2024.1400664

Keywords: Cell, spreading, viability, single-walled, carbon, nanotube, zinc, oxide, nanowire, heterostructures, synthesized, chemical

The study, published in Science Advances, describes what the researchers call bulk ferroelectric heterostructures created within a bismuth ferrite-barium titanate ceramic. Rather than stacking ultrathin layers of different materials in a film, as is common in laboratory demonstrations of interface-driven phenomena, the team used a carefully controlled heat treatment to drive nanoscale elemental partitioning throughout the interior of a solid ceramic. The result is an interconnected network of bismuth-rich and barium-rich regions embedded within a coherent crystal lattice, effectively building millions of internal interfaces into a material that can be manufactured at scale.

Dr David Hall, Reader in Ceramics in the Department of Materials and the Henry Royce Institute at The University of Manchester, explained the significance of the approach. Many of the most interesting behaviours in ferroelectric materials have historically been confined to thin films, where interfaces can be carefully engineered, he noted. What the team has shown is that similar interfacial effects can be generated throughout a solid ceramic, creating new opportunities to control the electrical and mechanical behaviour of these materials. The distinction matters because thin films, however elegant their physics, are difficult to incorporate into the robust bulk components that real-world sensors and actuators demand.

The mechanism behind the transformation is as compelling as the outcome. Using atomic-resolution microscopy, spectroscopy and computational modelling, the researchers established that their heat treatment causes the constituent elements to segregate into chemically distinct nanoscale regions while the crystal lattice remains coherent across the boundaries between them. Because the two families of regions differ in composition, they generate local electric fields and elastic strain fields where they meet. Charged domain walls also form within this landscape. Together, these internal features act as built-in heterointerfaces, altering how the entire ceramic responds when electrical voltages or mechanical forces are applied to it.

The most striking consequence is thermal. The engineered material exhibits a Curie temperature of 824 degrees Celsius, the point above which ferroelectricity collapses, more than 350 degrees higher than the starting material. That margin is not an academic curiosity. Piezoelectric sensors are increasingly needed in engines, turbines, exhaust systems and industrial process monitoring, environments where temperatures routinely exceed the limits of conventional lead-free piezoceramics. The Manchester-led team reports that the ceramic maintained strong piezoelectric performance at temperatures relevant to industrial sensing and monitoring applications, suggesting the material could function where existing options struggle or fail outright.

Beyond temperature tolerance, the researchers demonstrated something arguably more conceptually provocative: programmable ferroelectric behaviour. By combining electrical or mechanical conditioning with thermal ageing, they were able to imprint preferred domain configurations into the material. Remarkably, these configurations remain recoverable even after the application of strong electrical fields, enabling reversible electromechanical responses that are often difficult to achieve in conventional bulk ferroelectrics. In one configuration, the team achieved large reversible shear strains, a property prized in actuator technologies where precise, repeatable mechanical displacement is the goal. The study also reports internal bias fields exceeding 8 megavolts per metre, substantially higher than those typically observed in traditional bulk ferroelectric materials, a characteristic that can stabilise performance against depoling and fatigue.

To appreciate why this matters, it helps to consider how the field arrived here. Piezoelectric ceramics function because their crystal structures lack a centre of symmetry, allowing mechanical stress to generate a voltage and vice versa. For decades, the dominant material has been lead zirconate titanate, or PZT, whose exceptional properties come partly from a morphotropic phase boundary, a compositional knife-edge where two crystal phases coexist and switching between them becomes extraordinarily easy. Designing lead-free systems around similar phase boundaries has been a central strategy, but the resulting materials often sacrifice temperature stability or require delicate compositional tuning. The heterostructure approach takes a different philosophical route: instead of adjusting the average composition of the material, it engineers functionality directly into the material’s internal architecture.

The work is the product of an international collaboration involving The University of Manchester, the Henry Royce Institute, ShanghaiTech University, the Chinese Academy of Sciences, Diamond Light Source, the University of Leeds and Sheffield Hallam University. It also builds on roughly a decade of sustained research into lead-free piezoelectric ceramics at Manchester, an investment that has already yielded intellectual property protection for the underlying materials and the manufacturing approach. The research team is now supporting translation of the concept toward potential industrial applications, a step that will test whether laboratory-scale heat treatments can be reproduced reliably in commercial ceramic processing lines.

The implications extend past a single material system. Bismuth ferrite and barium titanate are both well-studied ferroelectrics, and the principle of using thermal processing to drive controlled nanoscale self-organisation could in principle be applied to other ferroic materials, including magnetic and multiferroic systems where internal interfaces are known to host unusual physics. Dr Hall framed the work as introducing a new design framework: rather than focusing solely on changing composition, researchers can use controlled nanoscale self-organisation to build new functionality directly into a material, a concept he suggested could apply across a much wider range of ferroic materials in future.

Challenges remain before bulk ferroelectric heterostructures reach the factory floor. Scaling any thermally driven microstructural process requires tight control of processing windows, and the long-term stability of the imprinted domain configurations under years of cyclic electrical and mechanical loading will need to be verified. Yet the demonstration that interface-driven effects, once thought to require atomically engineered thin films, can be reproduced inside a scalable ceramic represents a genuine conceptual advance. If the approach matures, it could reshape how engineers design the sensors that monitor jet engines, the transducers that power medical ultrasound, and the actuators that drive precision machinery, all while removing lead from the supply chain. For a field that has spent two decades searching for a viable route beyond PZT, the idea that the answer may lie in teaching materials to organise themselves is an unexpectedly elegant one.

Subject of Research: Lead-free piezoelectric bulk ferroelectric heterostructures in bismuth ferrite-barium titanate ceramics

Article Title: Bulk ferroelectric heterostructures open new design route for lead-free piezoelectric materials

Article References: Bulk ferroelectric heterostructures open new design route for lead-free piezoelectric materials. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: ferroelectric, piezoelectric, lead-free ceramics, bismuth ferrite, barium titanate, heterostructures, Curie temperature, high-temperature sensors, actuators, ultrasonic transducers, domain engineering, Science Advances

The secret to cobalt’s versatility lies in its electronic structure. The element sits in the middle of the transition-metal series, where its 3d orbitals are neither too full nor too empty, giving it access to multiple oxidation states, most commonly Co2+ and Co3+, and sometimes Co4+. That multivalent redox flexibility means cobalt atoms can readily exchange electrons with their surroundings, a property that underpins nearly every application the review describes. In a supercapacitor electrode, cobalt centers shuttle between oxidation states to store charge reversibly at the surface. In an electrocatalyst, they mediate the multi-electron transfers required to split water into hydrogen and oxygen. In a photocatalyst, they help capture and steer the charge carriers generated when light strikes a semiconductor. Add in cobalt’s strong magnetic behavior, its two accessible crystal phases, hexagonal close-packed and face-centered cubic, and its good electrical conductivity, and the result is a material platform with an unusually wide design space.

The review devotes considerable attention to how cobalt-based materials are actually made, because synthesis route often determines performance as much as composition does. Solid-state reactions, in which powders are ground and heated to high temperatures, remain the workhorse for producing robust thermoelectric ceramics such as the layered cobalt oxide Ca3Co4O9 and the skutterudite CoSb3. Hydrothermal and solvothermal methods, which crystallize materials from hot pressurized solutions, offer finer control over particle size and morphology, yielding everything from mesoporous Co3O4 nanorods for lithium-ion battery anodes to cobalt sulfide nanoflakes grown directly on carbon cloth for flexible supercapacitors. Electrodeposition provides a fast, room-temperature route to films such as CoSe2 counter electrodes for dye-sensitized solar cells, while template-assisted and sol–gel approaches, sometimes performed in ionic liquids or assisted by microwaves, allow chemists to sculpt porosity and doping profiles with precision. The authors emphasize that compositional engineering, defect modulation, and heterostructure design are the three levers that transform these syntheses from routine chemistry into performance tuning.

Thermoelectric materials, which convert temperature gradients directly into electricity, form one of the review’s central pillars. Cobalt-based compounds excel here because of an unusual combination of high electrical conductivity and complex crystal structures that scatter heat-carrying phonons. Layered cobalt oxides such as Ca3Co4O9 have attracted interest for high-temperature applications, and recent work shows that doping the calcium site with gadolinium enhances thermoelectric transport through spin entropy and size effects. Meanwhile, cobalt antimonide skutterudites, CoSb3, have become one of the most intensively studied thermoelectric families in the world. Filling the empty cages of the skutterudite crystal with guest atoms such as ytterbium, substituting nickel or aluminum onto the framework, and introducing nano-inclusions all serve to suppress lattice thermal conductivity while preserving or even boosting the power factor. The review also highlights half-Heusler alloys such as ZrCoBi, which have achieved high conversion efficiencies, and cobalt telluride–selenide solid solutions and thin films that push performance in the mid-temperature range.

On the energy storage front, cobalt compounds have become staples of supercapacitor research, where they operate through fast surface redox reactions known as pseudocapacitance. Spinel cobalt oxides such as Co3O4, binary metal oxides like NiCo2O4, and cobalt sulfides, selenides, and tellurides all offer abundant electroactive sites and favorable charge-transport characteristics. The review traces how researchers have boosted capacitance by pairing cobalt with nickel, copper, manganese, or zinc in bimetallic and even ternary oxides, and by growing hierarchical nanostructures that expose more surface area to the electrolyte. Cobalt-based metal–organic frameworks, porous crystalline solids in which cobalt ions are linked by organic struts, have emerged as a particularly exciting electrode class, with layered cobalt MOFs demonstrating ultrahigh capacities and MOF-derived composites, sometimes made by rapid cold plasma synthesis on reduced graphene oxide, delivering both high areal capacitance and operational stability.

Electrocatalysis for water splitting is another arena where cobalt shines, largely because it is far more abundant and cheaper than the noble metals that traditionally dominated the field. The review surveys cobalt-based catalysts for both the hydrogen evolution reaction and the oxygen evolution reaction, the sluggish half-reaction that limits overall water-splitting efficiency. Bimetallic iron–cobalt sulfides show synergistic activity, cobalt phosphide nanoflowers have been adapted for zinc-ion batteries, and cobalt-containing bimetallic zeolitic imidazolate frameworks and their derivatives serve as efficient oxygen evolution catalysts. Spin states of the metal centers, the review notes, play a decisive role in determining how strongly reaction intermediates bind to the surface, making spin engineering a frontier topic. Core–shell bimetallic catalysts are even being applied to carbon dioxide hydrogenation for light-hydrocarbon synthesis, extending cobalt’s reach into carbon utilization.

Perhaps the most environmentally resonant section of the review concerns photocatalysis, the use of light-activated materials to break down organic pollutants in water. Cobalt oxides, cobalt sulfides, and cobalt MOFs have all been shown to degrade dyes such as methylene blue, rhodamine B, methyl orange, crystal violet, and malachite green under ultraviolet or visible light. Strategies for improving performance include doping, for example tin-doped Co3O4 or neodymium-doped Co3O4 for enhanced visible-light activity, constructing heterojunctions such as Co3O4/Bi2O3 and CoO/ZnO that separate photogenerated electrons and holes more effectively, and building Z-scheme and S-scheme architectures that combine strong oxidation and reduction power without sacrificing light absorption. Cerium–cobalt bimetallic MOFs with mixed ligands, cobalt telluride nanosheets, and Co-MOF composites with bacterial cellulose or graphitic carbon nitride illustrate how far heterostructure design has progressed. The review links these gains to improved charge separation, broader light harvesting, and faster surface reaction kinetics.

None of this progress is without caveats, and the authors are candid about the obstacles standing between laboratory breakthroughs and real-world deployment. Long-term stability remains a concern for many cobalt catalysts and electrodes, which can degrade, dissolve, or restructure under operating conditions. Cobalt compounds carry known toxicity risks, and the element’s environmental and biological footprint, from mining impacts to potential leaching, demands careful management. Large-scale synthesis is another bottleneck: hydrothermal autoclaves and template methods that work beautifully at the gram scale are not trivially translated to the ton scale, and scaling considerations for water-splitting catalysts have been flagged as a broader challenge in the field. Cost and supply-chain concentration add further pressure, since cobalt is a strategically sensitive raw material.

The review closes with a forward-looking agenda that reads as a roadmap for the next decade of cobalt research. Interface engineering, deliberately designing the boundaries between cobalt phases and their supports to accelerate charge transfer, tops the list, followed by defect regulation, in which vacancies, dopants, and interstitial atoms are used as atomic-scale control knobs for electronic and catalytic properties. Sustainable synthesis routes, including plant-extract and biopolymer-assisted methods that replace harsh reagents, are gaining momentum, and advanced hybrid architectures that couple cobalt compounds with graphene, carbon nitride, conductive polymers, or biodegradable chitosan matrices promise multifunctional devices that simultaneously store energy, generate power from heat, and clean water. For a metal that already powers the batteries in electric vehicles, the review makes a persuasive case that cobalt’s scientific story is only beginning, and that rational design at the level of crystal phase, defect, and interface will determine how much of its potential the world ultimately captures.

Subject of Research: Cobalt-based functional materials for thermoelectric, electrochemical energy storage, and photocatalytic applications

Article Title: Recent advances in elemental cobalt and cobalt-based compounds for thermoelectric, electrochemical, and photocatalytic applications: a comprehensive review

Article References: Keerthana, M., Sahana, B. V., Swetha, R., Kruthika, S., & Kumari, L. (2026). Recent advances in elemental cobalt and cobalt-based compounds for thermoelectric, electrochemical, and photocatalytic applications: a comprehensive review. Ionics. https://doi.org/10.1007/s11581-026-07508-w

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07508-w

Keywords: cobalt, thermoelectric materials, supercapacitors, electrocatalysis, photocatalysis, cobalt oxides, cobalt chalcogenides, metal-organic frameworks, water splitting, energy storage, heterostructures, wastewater treatment

The work, published in Advanced Composites and Hybrid Materials, tackles a problem that has haunted fuel cell developers for decades. Conventional catalysts consist of platinum nanoparticles dispersed on carbon black, a material known in the trade as Pt/C. The bond between platinum and plain carbon is weak, so under the harsh, acidic, voltage-cycling conditions inside a working fuel cell, the tiny platinum particles gradually dissolve, migrate, and clump together. As the particles merge, the amount of exposed catalytic surface shrinks, and the fuel cell steadily loses power. The new study identifies this weak metal-support interaction as the root cause of the instability and sets out to fix it not by adding more platinum, but by rewiring the electrons at the interface.

The researchers’ strategy, which they call interfacial charge engineering, involves constructing heterostructures in which platinum is intimately coupled to molybdenum carbide, Mo2C, all supported on nitrogen-doped carbon. Molybdenum carbide is a fascinating material in its own right; sometimes nicknamed the ceramic that behaves like a metal, it conducts electrons well and forms strong chemical bonds with noble metals. By bringing platinum and molybdenum carbide into direct contact, the team created an interface where electrons are no longer content to stay put. Instead, charge redistributes directionally across the junction, and it is this deliberate electronic rearrangement that lies at the heart of the catalyst’s remarkable performance.

Manufacturing such precisely tuned nanoscale architectures is often the stumbling block that separates elegant laboratory concepts from practical technology. Here the team employed a scalable synthesis based on in-situ concurrent pyrolysis and reduction, a one-step thermal process in which the precursor materials transform simultaneously into the final composite. Rather than assembling platinum particles and carbide supports separately and hoping they bond, the method grows the heterostructure directly, ensuring that the electronic coupling between the two phases is established from the moment of formation. That scalability matters enormously for any catalyst hoping to leave the laboratory, since fuel cell deployment on the scale required for a hydrogen economy demands manufacturing routes that do not depend on painstaking, batch-by-batch nanofabrication.

Proving that the platinum and molybdenum carbide truly interact at the electronic level required sophisticated structural detective work. The team turned to X-ray absorption fine structure spectroscopy, a synchrotron-based technique that reveals the local atomic environment of specific elements. The measurements uncovered a distinct platinum-molybdenum bond measuring approximately 2.72 angstroms, with a platinum-molybdenum coordination number of about 1.81. In plain terms, each platinum atom at the interface is directly bonded to roughly one to two molybdenum neighbors, a signature of genuine chemical contact rather than mere physical proximity. This direct bonding is the structural foundation on which the entire charge-engineering concept rests, because electrons can only flow efficiently between phases that are chemically connected.

Theoretical calculations using density functional theory, performed on the Hefei Advanced Computing Center, illuminated what that charge flow actually does. The heterostructured interface, the computations showed, functions as an electronic reservoir, pulling and pushing charge in a directed manner across the platinum-molybdenum carbide boundary. The consequence is a downshift of the d-band center of the interfacial platinum atoms, a fundamental descriptor in catalysis theory that governs how strongly molecules stick to a metal surface. When the d-band center sits too high, oxygenated intermediates such as hydroxyl species bind too tightly and refuse to leave, poisoning the surface. By lowering the d-band center, the charge redistribution weakens those over-strong bonds just enough, optimizing the binding strength of oxygenated intermediates and allowing the reaction to proceed faster.

The electrochemical results were striking. The engineered Pt-Mo2C/NC catalyst delivered a mass activity of 0.65 amperes per milligram of platinum at 0.9 volts, the benchmark potential used to compare oxygen reduction catalysts worldwide. That figure represents a 4.8-fold improvement over commercial Pt/C, meaning the new catalyst extracts nearly five times more current from every precious gram of platinum. Since platinum can cost more than gold and fuel cell economics hinge on minimizing the platinum loading, multiplying its efficiency by nearly five is precisely the kind of leap that could reshape the cost calculations for hydrogen vehicles and stationary power systems alike.

Activity alone, however, has never been the fuel cell industry’s hardest problem; durability is. A catalyst that performs brilliantly on day one but fades within weeks is commercially useless, and this is where the interfacial design truly shines. The robust platinum-molybdenum carbide coupling anchors the platinum atoms in place and effectively suppresses both dissolution and agglomeration, the twin killers of conventional catalysts. After 20,000 potential cycles, an accelerated stress test that simulates years of start-stop driving, the catalyst retained approximately 90 percent of its initial mass activity. For comparison, conventional platinum-on-carbon catalysts typically lose far more of their activity under equivalent testing, which is exactly why the weak metal-support interaction was flagged as the central obstacle in the first place.

What makes this study resonate beyond a single material system is the generality of its design principle. Rather than discovering an accidental winner, the researchers demonstrated a rational recipe: choose a support that forms strong interfacial bonds with the catalytic metal, engineer directional charge transfer across that interface, and use the resulting electronic modulation to tune the binding energies of reaction intermediates. The same logic could, in principle, be applied to other catalytic metals and other carbide, nitride, or phosphide supports, opening a pathway toward a whole family of active, durable electrocatalysts designed from first principles rather than trial and error. The work also underscores how modern synchrotron spectroscopy and computational chemistry now work hand in hand, allowing scientists to see the bonds they are engineering and predict their consequences before a single electrochemical test is run.

The road from a published paper to a commercial fuel cell stack is long, involving membrane electrode assembly integration, real-world impurity tolerance, and mass production at scale, and the study, released as an open-access article with a permanent DOI, will now face the scrutiny of the wider electrocatalysis community. Yet the combination of a scalable synthesis, a mechanistic understanding grounded in atomic-scale evidence, and durability numbers that survive a punishing 20,000-cycle stress test gives this interfacial charge engineering strategy a credibility that many catalyst reports lack. If the approach transfers smoothly from the rotating disk electrodes of the laboratory to the membrane electrode assemblies of real fuel cells, the humble interface between a platinum atom and a molybdenum carbide support may come to be remembered as the place where the hydrogen economy finally found its footing, one carefully redistributed electron at a time.

Subject of Research: Interfacial charge engineering of platinum-molybdenum carbide heterostructures for the oxygen reduction reaction in fuel cells

Article Title: Interfacial charge engineering of Pt-Mo2C heterostructures for robust oxygen reduction reaction

Article References: Han, Y., Wang, Y., Wang, Q., Zheng, X., Lu, S., Zeng, Y., Hua, Q., Jia, C., Donkor, S., & Xu, B. B. (2026). Interfacial charge engineering of Pt-Mo2C heterostructures for robust oxygen reduction reaction. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02109-7

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02109-7

Keywords: oxygen reduction reaction, fuel cells, platinum catalyst, molybdenum carbide, interfacial charge engineering, electrocatalysis, heterostructures, metal-support interaction, d-band center, catalyst durability, X-ray absorption spectroscopy, density functional theory

MXenes earned their name from their layered MAX-phase parents, with M standing for transition metals such as titanium, vanadium, niobium, or molybdenum, X for carbon or nitrogen, and the suffix echoing graphene to signal a two-dimensional structure. First synthesized in 2011, when Ti3AlC2 particles were submerged in hydrofluoric acid to strip out the aluminum layers, these accordion-like multilayer sheets can be delaminated into thin, transparent nanosheets with enormous surface area. Unlike graphene or carbon nanotubes, which rely mainly on electrostatic charge storage and often require extra functionalization, MXenes combine intrinsic metallic conductivity with hydrophilic surfaces decorated with oxygen, hydroxyl, and fluorine terminations. That combination enables pseudocapacitive charge storage, rapid ion transport, and strong interfacial bonding with metals, sulfides, phosphides, and semiconductor partners.

The review devotes considerable attention to synthesis, because the production route largely dictates surface chemistry and electrochemical behavior. Hydrofluoric acid etching remains the classical method, but safer in situ etching using fluoride salts with hydrochloric acid, hydrothermal etching in sealed autoclaves, solvothermal processing, electrochemical etching, and fluorine-free molten salt routes have all expanded the toolkit. Lewis acidic molten salt etching with zinc chloride, for example, can produce chlorine-terminated MXenes with controlled surface chemistry, while microwave-assisted approaches can deliver MXenes in minutes. The authors stress that no single fabrication strategy satisfies every requirement for practical electrodes, so rational matching of synthesis technique to application remains essential.

On the energy-storage front, MXene-based supercapacitors have progressed dramatically since the first demonstration in 2013. A binder-free Ti3C2Tx paper electrode produced by vacuum filtration achieved a volumetric capacitance of 350 F cm-3 in potassium hydroxide electrolyte, matching advanced graphene systems, and later LiF/HCl-etched clay films pushed volumetric capacitance to roughly 900 F cm-3. Composite engineering has multiplied these gains. Manganese dioxide nanowhiskers grown directly on MXene surfaces delivered around 212 F g-1 with 87.7% retention after 10,000 cycles, while MXene/PANI hybrids fabricated through oxidant-free in situ polymerization reached approximately 503 F g-1 and 1682 F cm-3, retaining 98.3% of their capacitance after 10,000 cycles even at thick, high-mass-loading electrodes. Sandwich-like heterostructures combining bimetallic sulfides with Ti3C2Tx have reported specific capacitances as high as 2637 F g-1 and device-level energy densities near 80 Wh kg-1.

These performance leaps rest on a charge-storage mechanism that uniquely blends electric double-layer capacitance with fast, reversible surface redox reactions. Electrolyte ions adsorb onto the conductive MXene sheets while the terminal groups mediate Faradic processes involving protons or alkali-metal cations. In acidic media, proton-coupled surface redox dominates; in neutral and alkaline electrolytes, hydrated cation intercalation between expanded interlayers becomes the key factor. Strategies such as interlayer pillaring, which can widen the spacing to 3.2 nanometers, heteroatom doping, defect engineering via plasma-assisted mechanochemistry, and deliberate vacancy creation in vanadium-based MXenes all enhance ion accessibility and active-site density, though excessive defects can compromise structural stability.

The second half of the review turns to electrocatalytic water splitting, where water is decomposed into hydrogen and oxygen through the hydrogen evolution reaction at the cathode and the more sluggish four-electron oxygen evolution reaction at the anode. Theoretical work indicates that oxygen-terminated MXenes approach the ideal near-zero hydrogen adsorption free energy required for efficient HER. Experimental systems have validated this promise: a platinum-anchored vanadium carbide MXene achieved a 27 mV overpotential at 10 mA cm-2 with a Tafel slope of 36.5 mV dec-1, while ruthenium-incorporated cobalt phosphide on MXene delivered overpotentials of just 9 mV in alkaline media and about 97% voltage retention over 200 hours. Molybdenum disulfide quantum dots on Ti3C2Tx, Ru single atoms and clusters on molybdenum carbide MXene, and nitrogen-doped Ti2CO2 designed through density functional theory all illustrate how MXene supports accelerate charge transfer and water dissociation.

For oxygen evolution, MXenes excel primarily as conductive, stabilizing supports for catalytically active species. High-entropy oxides grown on MXene nanosheets by rapid microwave heating produced a Tafel slope of 71 mV dec-1 and strong photoelectrochemical activity, whereas bimetallic NiFe-Ti3C2Clx MXene hybrids formed through molten salt synthesis reached 310 mV overpotential with Ni centers identified as the dominant active sites. Metal-organic-framework-derived nickel-cobalt sulfide on ultrathin MXene sheets and oxygen-vacancy-engineered FeOOH arrays on Ti3C2Tx, the latter outperforming commercial iridium oxide in stability tests exceeding 100 hours, underscore how heterostructure and doping strategies convert MXene limitations into synergistic advantages.

Perhaps the most commercially consequential advance involves bifunctional electrocatalysts that perform both HER and OER in a simplified two-electrode electrolyzer. Triple-interface Ni3Se4-NiSe2-Co3O4 heterostructures on MXene reached 100 mA cm-2 at a cell voltage of only 1.64 V with 100 hours of stable operation, while L-tryptophan-anchored CoNi-Ti3C2Tx split water at 1.58 V and sustained an industrially relevant 500 mA cm-2 at 1.87 V in an anion-exchange membrane electrolyzer. Ultrafine ruthenium-cobalt nanoparticles on MXene required just 1.52 V with near-100% Faradaic efficiency, and a low-cost multi-hybrid MXene/Mn3O4/CuO composite maintained stability for twelve days. The authors argue these systems bridge the gap between laboratory metrics and real-world hydrogen production.

Significant hurdles remain before MXene technologies reach the market. Oxidation instability remains the foremost concern, as pristine nanosheets degrade in air, water, and light, converting conductive carbides into insulating titanium dioxide and eroding capacitance. Nanosheet restacking suppresses ion transport, hydrofluoric acid etching raises environmental and scalability questions, surface terminations are difficult to control reproducibly, and precursor costs complicate mass production. Countermeasures are maturing rapidly, including edge capping with polyanionic salts, cold storage under inert conditions, polymer encapsulation, and three-dimensional aerogel architectures. Looking ahead, the review calls for green etching chemistry, defect and interface engineering, machine-learning-guided materials discovery, solid-state and wearable supercapacitor designs, and stronger academia-industry collaboration to carry MXenes from the laboratory bench toward sustainable energy storage and industrial-scale clean hydrogen generation.

Subject of Research: MXene nanomaterials for next-generation supercapacitors and electrochemical water splitting

Article Title: Recent advances of MXene as a frontier nanoarchitecture in energy science for shaping the future of next-generation supercapacitor and water splitting technology

Article References: Sau, A., Hassan, T., Mitra, S., Ghosh, S., Basu, R., & Das, S. (2026). Recent advances of MXene as a frontier nanoarchitecture in energy science for shaping the future of next-generation supercapacitor and water splitting technology. Discover Electrochemistry, 3(1), Article 70. https://doi.org/10.1007/s44373-026-00156-9

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00156-9

Keywords: MXene, supercapacitors, water splitting, hydrogen evolution reaction, oxygen evolution reaction, two-dimensional materials, energy storage, electrocatalysis, pseudocapacitance, heterostructures, surface functionalization, green hydrogen

The appeal of TMDs begins with their unusual structure. With the general formula MX2, where M is a transition metal such as molybdenum, tungsten, niobium, or tantalum and X is sulfur, selenium, or tellurium, each monolayer consists of a sheet of metal atoms sandwiched between two sheets of chalcogen atoms. Adjacent layers are held together only by weak van der Waals forces, which means bulk crystals can be peeled into single-atom-thick sheets. This architecture yields enormous surface-area-to-volume ratios, coordinatively unsaturated edge atoms with dangling bonds that serve as natural binding sites for reactive intermediates, and interlayer galleries that can host rapid ion transport. These are precisely the features that electrochemical energy devices demand.

Yet pristine TMDs carry intrinsic handicaps. The thermodynamically stable 2H phase is semiconducting, which limits charge transport; the basal plane is chemically inert and contributes little to catalysis; and narrow interlayer spacing slows ion intercalation. Exfoliated nanosheets also tend to restack during device fabrication, degrading stability and cycling performance. The review’s central message is that these limitations are not dealbreakers but design opportunities, addressable through a toolkit that includes defect engineering, heteroatom doping and alloying, strain engineering, atomic-scale modulation, nanostructure design, interlayer and phase control, and heterostructure fabrication.

Defect engineering has proven especially powerful. Sulfur vacancies in molybdenum disulfide create donor states within the band gap and expose undercoordinated metal atoms that bind hydrogen favorably. One highlighted study used high-throughput density functional theory calculations to identify the optimal vacancy configuration, then developed a hydrogen peroxide chemical etching method to distribute single sulfur vacancies uniformly across MoS2 nanosheets. The resulting catalyst achieved a hydrogen evolution overpotential of just 131 millivolts at 10 milliamperes per square centimeter, with a Tafel slope near 48 millivolts per decade and excellent stability. The authors caution, however, that defects cut both ways: they can also act as scattering centers and trap states that degrade carrier mobility, so passivation of harmful defects must accompany the deliberate introduction of useful ones.

Doping and alloying offer complementary control over electronic structure. When researchers doped MoS2 with zinc using a fusion heat method, X-ray photoelectron spectroscopy revealed binding energy shifts of roughly 0.47 and 0.40 electron volts for the Mo 3d and S 2p levels, indicating increased electron density that accelerates the hydrogen discharge step. Bimetallic strategies push further: cobalt-doped MoS2 works bifunctionally in both acidic and alkaline water splitting, while ruthenium doping wrapped in carbon nanotubes activates the otherwise inert 2H basal plane. Alloying enables continuous band gap tuning, with CVD-grown MoS2(1-x)Se2x films showing more than ten percent band gap modulation and quaternary alloys spanning 1.60 to 2.03 electron volts. Remarkably, doping can even trigger phase transitions, as rhenium concentrations above 40 percent stabilize the metallic 1T-prime phase of MoSe2.

Strain engineering adds another dimension. Because TMD monolayers can withstand more than 20 percent elastic distortion, mechanical deformation directly reshapes their band structure. Computational work predicted that only 0.3 to 3 percent uniaxial tensile strain converts 1H-MoTe2 into the quasi-metallic 1T-prime phase at room temperature, and experiments confirmed strain-induced band gap tuning in MoS2. The most striking results come from combining strain with vacancies: when sulfur vacancies in monolayer 2H-MoS2 were simultaneously strained, gap states shifted toward the Fermi level, yielding near-optimal hydrogen adsorption free energy. The combined system showed a Tafel slope of 60 millivolts per decade versus 98 for pristine MoS2, and the turnover frequency of its molybdenum atoms exceeded even that of conventional edge sites.

Phase engineering targets the most consequential lever of all. The metallic 1T phase of MoS2 conducts electricity roughly ten million times better than the semiconducting 2H phase and is hydrophilic, both critical for electrochemistry. Chemically exfoliated 1T-MoS2 reaches benchmark hydrogen evolution current densities at around 187 to 195 millivolts versus RHE, compared with more than 300 millivolts for the 2H phase, with Tafel slopes dropping from about 110 to the mid-40s. Because 1T is metastable and reverts to 2H near 92 degrees Celsius, researchers have developed stabilization tricks including sulfur intercalation, metal cation insertion, and palladium doping that partially converts the phase and slashes Tafel slopes from 157 to as low as 62 millivolts per decade.

Heterostructures and single-atom catalysts round out the toolkit. Coupling MoS2 with WTe2 creates a low Schottky barrier at the interface that shortens electron transport paths from micrometers to roughly 700 picometers, dramatically improving charge injection. Covalent 0D-2D hybrids of Co9S8 nanoparticles bonded to MoS2 through Co-S-Mo links render molybdenum sites electron-rich and activate the basal plane across all pH values. Meanwhile, isolated nickel atoms anchored on MoS2 nanofibers cut hydrogen evolution overpotentials from 263 to 161 millivolts, and nickel-oxygen sites engineered onto 1T-MoS2 achieved an onset potential near 0 volts with an overpotential of only 46 millivolts in alkaline media. In photocatalysis, single-layer 1T-MoS2 paired with nitrogen-doped graphene produced hydrogen roughly 600 times faster than comparable 2H systems under visible light.

Energy storage results are equally compelling. Vertically aligned metallic MoS2 on graphene delivered initial lithium-ion capacities near 1700 milliampere-hours per gram, while carbon-free metallic nanotube anodes retained the 1T phase for at least 120 days in air. For sodium-ion batteries, freestanding 1T-MoS2 grown on hollow graphene foam sustained stable capacities around 313 milliampere-hours per gram over 200 cycles. Supercapacitors built from restacked 1T-MoS2 films achieved volumetric capacitances of 400 to 650 farads per cubic centimeter, retaining over 93 percent of initial capacitance after 5000 cycles, and water-coupled metallic MoS2 with nanochannels reached 150 farads per gram even without conductive additives. The review concludes that scalable synthesis, long-term phase stability, and clear structure-property correlations remain the key hurdles, and it points to artificial intelligence-assisted materials discovery as the accelerant that could carry these engineered atomically thin catalysts from laboratory demonstrations to industrial deployment.

Subject of Research: Materials engineering strategies for tuning metallic two-dimensional transition metal dichalcogenides for energy conversion and storage

Article Title: Recent advances in tuning the properties of metallic 2D transition-metal dichalcogenides for energy conversion and storage

Article References: Ha, J., Park, G., Kang, G., Kang, J., Bak, H., Lee, D., Lee, H., Cho, K., & Kim, Y. (2026). Recent advances in tuning the properties of metallic 2D transition-metal dichalcogenides for energy conversion and storage. Advances in Industrial and Engineering Chemistry, 2(1), Article 5. https://doi.org/10.1007/s44405-026-00045-0

Image Credits: AI Generated

DOI: 10.1007/s44405-026-00045-0

Keywords: transition metal dichalcogenides, two-dimensional materials, hydrogen evolution reaction, phase engineering, defect engineering, heteroatom doping, strain engineering, heterostructures, lithium-ion batteries, supercapacitors, electrocatalysis, energy storage