The catalysts were synthesized hydrothermally as roughly 20-nanometer nanoflowers dispersed on carbon, then annealed at 700 degrees Celsius to fuse them into larger, highly crystalline nanoparticles. Transmission electron microscopy and selected-area electron diffraction confirmed the phase transition from the as-made face-centered-cubic structure to the chemically ordered L10 phase, in which alternating platinum-rich and iron/cobalt-rich atomic columns stack in a regular superlattice. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy resolved those alternating bright and dim atomic columns directly, while X-ray diffraction showed the characteristic (001), (110), (111), (200), (220) and (311) reflections of L10-FePt, with the (111) peak shifting to higher angles as cobalt, the smallest of the three metal atoms, was incorporated. Five compositions spanning Fe-to-Co ratios from roughly 22:18 to 12:53 against a platinum fraction between 35 and 60 percent were prepared simply by varying the cobalt precursor.

X-ray photoelectron spectroscopy revealed that composition does far more than dilute the platinum: it reverses the direction of interatomic electron transfer. In the mid-cobalt sample FeCoPt-2, platinum and cobalt donate electron density to iron, pushing the Pt 4f peaks to the highest binding energies of the series. In the cobalt-rich FeCoPt-4, the trend flips, and platinum becomes the electron acceptor, sitting at the lowest Pt binding energy. That accumulated negative charge on platinum weakens the adsorption of carbonaceous intermediates, which the authors link directly to catalytic performance. Electrochemical testing in acidic methanol bore this out: FeCoPt-4 delivered 0.9 amperes per milligram of platinum, the highest of the series, with a specific activity 28 times that of commercial Pt/C. Accelerated durability testing cost it only 10.2 percent of its peak current after 1000 cycles and 14.3 percent after 2000, far better than the 40.2 percent loss suffered by FeCoPt-2, and post-test microscopy and diffraction confirmed the L10 structure remained intact with only about 3 percent iron and 5 percent cobalt loss.

The real surprise came when an 8000-oersted magnetic field was switched on. The magnetic-field response, defined as the fractional change in the forward oxidation peak current, followed a volcano shape against cobalt content in both acidic and alkaline media, but the volcano peaks at different compositions in each electrolyte. In acid, FeCoPt-2, with 25 percent cobalt, showed the largest response at 13.3 percent; in alkali, it was FeCoPt-4, at 14.7 percent. Crucially, the sample with the highest intrinsic activity was never the one with the strongest magnetic response, a decoupling the team explains through the balance of adsorbed intermediates. In the bifunctional mechanism, platinum sites dehydrogenate methanol to CO*, while iron and cobalt sites split water to supply OH*, and the rate-determining step is the coupling of the two to release carbon dioxide. Where OH* is scarce, the field helps most by promoting its formation; where it is already abundant, the field instead works by weakening the platinum-carbon monoxide bond.

Le Chatelier’s principle provides the unifying frame. In alkaline solution, hydroxide ions are freely available, so the demand for field-assisted OH* generation drops and the optimum shifts to a lower-cobalt composition, FeCoPt-3, for peak activity. Methanol concentration plays the same equilibrium-shifting role. In 0.5 molar sulfuric acid, FeCoPt-4 performed best at 3 molar methanol, where molecular dynamics simulations suggest methanol and water arrive at the surface in near-equal numbers, the ideal stoichiometric balance for the reaction. In 1 molar potassium hydroxide, the activity optimum moved to 4 molar methanol, but the magnetic-field response kept climbing, reaching 36.8 percent at 7 molar methanol, thirty-one times the response measured at 1 molar. With hydroxide plentiful, methanol becomes the limiting reactant, and the field’s ability to weaken the Pt-CO bond is exploited most fully when CO* coverage is high.

First-principles calculations traced these trends to the d-band center, the energy yardstick of the Newns-Anderson model that links adsorption strength to the position of metal d-states relative to the Fermi level. As cobalt content rose, the iron d-band center climbed to its highest point, minus 0.498 electron-volts, in FeCoPt-2, opening more empty d-orbitals for hybridization with hydroxyl adsorbates, while the cobalt d-band center dipped to its lowest there. The platinum 5d center shifted upward with cobalt content, and the calculated value for platinum single crystal, minus 2.35 electron-volts, fell between the FeCoPt-3 and FeCoPt-4 models, consistent with the observed reversal of electron-transfer direction. Formation-energy analysis confirmed the structures were sound, with FeCoPt-1 most stable at minus 0.045 electron-volts per atom and FeCoPt-5 unstable once platinum fell below the 45-to-55 percent window required for the L10 phase.

The spin-resolved calculations supplied the magnetic mechanism. Spin-up and spin-down densities of states are strongly split for iron and cobalt, and even platinum, normally treated as spin-agnostic, shows a small net spin aligned antiparallel to its 3d neighbors. The summed iron and cobalt net moments per unit cell rose from 0.34 to 0.58 Bohr magnetons across the series before falling in the unstable FeCoPt-5, and the largest iron moment appeared in FeCoPt-2, the acid-phase champion of magnetic response, while the largest cobalt moment appeared in FeCoPt-4, the alkaline champion. Under an applied field, the spin-down bands of all three elements shift toward the Fermi level while spin-up bands move away, and the splitting of the iron d-band centers reached 2.889 electron-volts in FeCoPt-2. Spin-down electrons, sitting closest to the Fermi level, act as the hot electrons of catalysis, and their upward shift opens vacant orbitals to couple with CO* and OH*. Adsorption-energy calculations showed the field strengthens OH* binding at iron sites while weakening it at cobalt sites, and flips the platinum-site OH* adsorption energy negative, together accelerating hydroxyl turnover.

Gibbs free-energy profiles put a number on the payoff. For FeCoPt-4, the barrier of the rate-determining CO-plus-OH step drops from 1.83 electron-volts in the antiferromagnetic, zero-field configuration to 1.22 electron-volts in the ferromagnetic state that mimics the magnetized catalyst, a 0.61 electron-volt reduction that makes methanol oxidation dramatically easier. Disorder simulations reinforced the importance of the ordered L10 lattice: atomic exchange, atomic displacement, and platinum point defects all destabilized the structure and shifted d-band centers in ways that either weakened hydroxyl adsorption or strengthened carbon monoxide binding, both detrimental. Grain size and lattice strain, the usual suspects in alloy catalysis, were systematically ruled out as drivers of the magnetic properties, leaving spin structure as the controlling variable.

The broader message is that electrocatalysis has an ignored quantum dial. Because iron, cobalt, and platinum are fully miscible, cobalt content tunes spin polarization continuously rather than in discrete jumps, something alloys built from manganese, bismuth, or chromium, which barely dissolve in platinum, cannot do. The study demonstrates that optimal performance emerges not from maximizing any single property but from balancing CO* and OH* coverages, a balance jointly set by composition, pH, methanol concentration, and now magnetic field. The authors point toward operando quantification of the two intermediates as the next step, but the concept already sketches a route to direct methanol fuel cells in which a modest electromagnet, rather than ever-more-precious platinum engineering, provides an externally switchable boost to one of electrochemistry’s most stubborn reactions.

Subject of Research: Magnetic-field-assisted methanol oxidation on spin-tunable L10-FeCoPt alloy electrocatalysts

Article Title: Magnetic‐Field‐Tuned Spin‐Dependent D‐Band and Bifunctionality in L10‐FeCoPt for Enhanced Methanol Oxidation

Article References: Mo, Q., Liu, K., Liu, R., Juan, Y., Wang, S., Liu, J., & Wang, W. (2026). Magnetic‐Field‐Tuned Spin‐Dependent D‐Band and Bifunctionality in L1 0 ‐FeCoPt for Enhanced Methanol Oxidation. Advanced Science, Article e78112. https://doi.org/10.1002/advs.78112

Image Credits: AI Generated

DOI: 10.1002/advs.78112

Keywords: methanol oxidation reaction, direct methanol fuel cells, FeCoPt alloy, L10 phase, d-band center, spin electrochemistry, magnetic field, bifunctional mechanism, CO poisoning, platinum catalysts, spin polarization, electrocatalysis

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

The starting materials belong to a family of cyanometallate coordination polymers with the general framework T[Fe(CN)₅NO], where T is a transition-metal ion. In the study, T was cobalt, nickel, or copper. Pyridine molecules bind to the outer metal centers and change the architecture from a three-dimensional bulk structure into layered two-dimensional sheets. This transformation is important because the parent nitroprussides have limited surface area and disperse poorly, whereas thin layers can be distributed across a conductive carbon support. Pyridine is therefore not introduced primarily as an oxygen-evolution promoter. Its principal role is structural: by selectively replacing axial metal–cyanide connections, it enables the layered morphology and helps stabilize neighboring sheets through pi–pi and dipole–dipole interactions. The resulting materials were combined with reduced graphene oxide in a one-to-one weight ratio. The graphene network provides pathways for electron transport and helps expose the coordination-polymer domains to the alkaline electrolyte.

Several complementary measurements confirmed that the metal identity altered both the structure and the electronic environment of the composites. X-ray diffraction showed layered materials with characteristic basal-plane reflections for the cobalt and nickel systems, while the copper composite displayed different stacking behavior. Electron microscopy revealed average particle sizes of approximately 133 nanometers for the cobalt material, 47 nanometers for the nickel material, and 214 nanometers for the copper material. Infrared and Raman spectroscopy detected the cyanide, nitrosyl, pyridine, and graphene-related signatures expected from the composite design. The cyanide stretching frequency shifted systematically as the metal changed from cobalt to copper, reflecting differences in the cations’ polarizing power. Raman measurements also indicated a defect-rich reduced graphene oxide support. The disorder can be useful in electrocatalysis because defects may create additional sites for oxygen-related reactions, although the measured surface area alone did not determine which composite performed best.

Electrochemical testing revealed a clear division of labor among the three materials. For OER in alkaline solution, the nickel composite showed the lowest onset potential and the strongest current response, reaching 10 milliamperes per square centimeter at an overpotential of about 398 millivolts. The cobalt and copper versions required approximately 437 and 518 millivolts, respectively, under the same benchmark. Nickel also exhibited the lowest charge-transfer resistance across the tested potential range. Cobalt, however, produced the lowest fitted OER Tafel slope, 61 millivolts per decade, compared with 74 for nickel and 156 for copper. The researchers caution that a lower Tafel slope by itself does not establish the fastest overall reaction; onset potential, overpotential, resistance, and operating conditions must be considered together. For ORR, the pattern reversed. The copper composite delivered the lowest onset potential and the highest limiting current, indicating the most favorable oxygen-reduction behavior among the tested materials.

Rotating-disk experiments provided further information about the oxygen-reduction pathway. Koutecky–Levich analysis indicated that all three composites predominantly followed a four-electron route, which is desirable in zinc-air batteries because it converts oxygen more directly and limits peroxide formation. The estimated electron-transfer numbers were approximately 3.95 for cobalt, 3.63 for nickel, and 3.97 for copper. The nickel value suggests that a mixture of four-electron and two-electron pathways may occur, potentially producing some hydrogen peroxide. The authors note that rotating-ring-disk measurements would be needed to investigate that possibility directly. Together, the half-cell results show why optimizing a rechargeable zinc-air battery is difficult: nickel favors the charging reaction, copper favors the discharging reaction, and neither is automatically the best complete-device material. The measurements instead point toward a compromise in which both reactions remain sufficiently active.

That compromise emerged when the composites were assembled into working zinc-air batteries. The cobalt-based cathode produced the highest peak power density, 54 milliwatts per square centimeter, narrowly exceeding the nickel system at 53 and clearly surpassing the copper system at 39. It also maintained higher discharge-voltage plateaus, particularly as the current density increased. During galvanostatic cycling at 10 milliamperes per square centimeter, the cobalt battery began with a voltage gap of 0.99 volts between charge and discharge and reached 1.18 volts after 24 hours. The corresponding gaps for copper were 1.05 and 1.29 volts, while nickel showed 1.43 and 1.36 volts. Initial round-trip energy efficiencies were 52 percent for cobalt, 50 percent for copper, and 34 percent for nickel. After the cycling period, they were 46, 42, and 33 percent, respectively. The cobalt device also retained a relatively stable impedance and delivered an average energy above 8.5 watt-hours per square meter per cycle.

The study’s central chemical finding is that the synthesized nitroprussides do not remain unchanged during battery operation. Post-cycling analysis of the best-performing cobalt electrode showed that the characteristic cyanide signal disappeared, while hydroxyl and metal–oxygen signatures emerged. X-ray diffraction and Raman spectroscopy likewise indicated conversion into a cobalt hydroxide or oxyhydroxide phase. The original material is therefore a precursor rather than the final catalyst. Importantly, X-ray photoelectron spectroscopy detected a pyridinic nitrogen signal after cycling, suggesting that the pyridine ligand remained associated with the reconstructed active phase instead of being completely lost. The researchers propose that the retained molecules act as structural pillars and electronic modifiers, helping prevent the newly formed oxyhydroxide sheets from agglomerating. The same alkaline environment that drives the battery reactions promotes this reconstruction. Similar hydroxide or oxyhydroxide phases are considered likely for the nickel and copper composites, although direct post-cycling structural confirmation was performed most extensively for cobalt.

Magnetic measurements offered an unusual window into the reconstructed electrodes, indicating that the active hydroxides are locally disordered rather than simple, perfectly ordered crystals. Measurements of magnetic susceptibility showed metal-dependent interactions, including antiferromagnetic correlations, weak ferromagnetic-like behavior, metamagnetic transitions, and magnetic relaxation. The cobalt and nickel hydroxide phases displayed low-temperature features associated with competing or complex interactions, while the copper material showed behavior consistent with antiferromagnetic correlations and a distorted local environment. These observations matter because local disorder can change the electronic states available for binding oxygen intermediates. Valence-band X-ray photoelectron spectra placed the approximate d-band centers in the order nickel below cobalt below copper. Within the commonly used d-band framework, a higher d-band center can strengthen adsorption of oxygen intermediates, helping ORR but potentially making OER less favorable. The results fit that qualitative picture: copper was strongest for ORR, nickel for OER, and cobalt, with an intermediate electronic position, offered the best balance. The authors emphasize that the d-band values are approximate descriptors, not proof of a single causal mechanism.

The work presents coordination polymers as tunable molecular precursors for practical oxygen electrocatalysis, while also highlighting the limits of laboratory battery demonstrations. The cobalt composite approached a zinc-specific capacity of 809.2 milliampere-hours per gram at 5 milliamperes per square centimeter, close to the theoretical value of 820, but the researchers caution that this result reflects a relatively low current density, a high-purity zinc anode, and a particular concentrated alkaline electrolyte. Further studies will be needed to assess operation at higher rates, longer lifetimes, different electrolyte compositions, and larger electrode areas. In situ spectroscopy and density-functional calculations could also test how the retained pyridine, disordered hydroxide structure, and d-band position cooperate during cycling. Even with those questions unresolved, the comparison demonstrates a useful design principle: the best bifunctional catalyst is not necessarily the material that wins either half-reaction independently. In this series, deliberately balancing electronic structure, conductive architecture, and electrochemical reconstruction allowed the cobalt-based pre-electrocatalyst to deliver the most practical zinc-air battery performance.

The precursor strategy also addresses a practical materials challenge beyond catalytic activity. Conventional oxygen electrocatalysts often rely on platinum for reduction or iridium- and ruthenium-based oxides for evolution, but the scarcity and cost of these elements complicate deployment at scale. Nitroprusside coordination polymers offer a different platform because their metal sites, cyanometallate framework, and organic coordination environment can be varied systematically. The cobalt, nickel, and copper comparison therefore functions as a controlled probe of how first-row transition-metal chemistry affects a common molecular architecture, rather than as a simple search for a single universally optimal composition.

That architecture may be especially valuable for studying catalyst reconstruction under realistic operation. Because the electrochemically generated hydroxide is the working phase, evaluating only the pristine powder could obscure the properties that govern a battery’s behavior. The reported combination of spectroscopy, diffraction, microscopy, and magnetic susceptibility illustrates why identifying active materials requires measurements before and after polarization. It also suggests a broader design opportunity: coordination ligands can serve as temporary structure-directing components while influencing the local environment retained after conversion. Determining how much pyridine survives, where it is located, and whether its effect persists over extended cycling will be important for distinguishing a genuine electronic contribution from a short-lived synthesis advantage. Such questions are relevant to translating these composites from proof-of-concept electrodes into durable, scalable air-cathode materials.

Subject of Research: Transition-metal nitroprusside and reduced graphene oxide pre-electrocatalysts for rechargeable zinc-air batteries

Article Title: Pyridine-based nitroprussides coupled to reduced graphene oxide as bifunctional pre-electrocatalysts for zinc-air batteries

Article References: Quintanilla-Serrano, E. A., Acevedo-Peña, P., Ávila, Y., González, M., & Reguera, E. (2026). Pyridine-based nitroprussides coupled to reduced graphene oxide as bifunctional pre-electrocatalysts for zinc-air batteries. Discover Electrochemistry, 3(1), Article 77. https://doi.org/10.1007/s44373-026-00164-9

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00164-9

Keywords: zinc-air batteries, electrocatalysis, reduced graphene oxide, nitroprussides, oxygen reduction, oxygen evolution, cobalt hydroxide, d-band center, Pyridine-based, coupled, reduced, graphene