Electrolyzers split water into hydrogen and oxygen using two complementary half-reactions: the hydrogen evolution reaction (HER) at the cathode, where protons or water molecules are reduced to hydrogen gas, and the oxygen evolution reaction (OER) at the anode, a slower, more energy-demanding four-electron process that liberates oxygen. The efficiency losses in a practical electrolyzer stem largely from the overpotentials—excess voltage beyond thermodynamic minimum—needed to push these reactions at useful rates. Platinum and iridium oxide are the standard benchmarks for HER and OER respectively, but their scarcity and cost make them poor candidates for gigawatt-scale hydrogen production. Bifunctional catalysts that can perform both reactions allow a single material to serve as both the cathode and the anode in a two-electrode cell, simplifying device design and cutting costs dramatically.

The new material, designated Ni₁Co₃@CN-sh, was synthesized through a straightforward pyrolysis route. The researchers, led by Muxi Wang, Wenwen Luo, Guang Li, and Qingfeng Yi of Hunan University of Science and Technology, together with Ruowei Yi of Xiangtan University, modulated two key variables: the nickel-to-cobalt ratio in the metallic nanoparticles and the choice of organic compound used as the carbon source. By carefully tuning these parameters, they produced a catalyst in which NiCo alloy nanoparticles are dispersed on flaky, nitrogen-containing carbon sheets that assemble into a three-dimensional hierarchical porous architecture. This porous structure is not merely cosmetic; it provides an abundance of electrochemically accessible active sites, channels for rapid electrolyte penetration, and interconnected pathways for the electrons that must shuttle between the metal particles and the external circuit during catalysis.

The performance numbers reported for the optimal composition are striking. For the oxygen evolution reaction—widely considered the bottleneck of water electrolysis—the Ni₁Co₃@CN-sh catalyst required an overpotential of just 191 millivolts to reach a current density of 100 milliamperes per square centimeter, a figure that places it on par with commercial iridium dioxide, the noble-metal reference catalyst for OER. On the hydrogen side, the same material needed only 194 millivolts of overpotential, comparable to what commercial platinum-on-carbon delivers. Achieving such balanced performance from a single non-noble-metal catalyst is rare, because the atomic-scale requirements for the two reactions differ: HER favors surfaces with optimal hydrogen adsorption energy, while OER depends on the energetics of oxygen-containing intermediates and often benefits from in-situ surface reconstruction into higher-valent oxyhydroxide species.

Nickel and cobalt, as neighboring transition metals, offer a productive synergy that the authors exploited through composition control. Cobalt-rich compositions appear to optimize the electronic structure of the alloy nanoparticles, modulating the d-band position and thereby tuning adsorption energies for reaction intermediates on both catalyst surfaces. The nitrogen-doped carbon support contributes in its own right: graphitic and pyridinic nitrogen sites can tune the electronic structure of adjacent metal atoms, enhance charge transfer, and themselves contribute catalytic activity, while the flaky morphology of the carbon provides mechanical robustness and good electrical connectivity to the metal nanoparticles. The team characterized the material using a comprehensive suite of techniques including X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller surface area analysis, building a structural picture consistent with well-dispersed alloy particles anchored within the conductive carbon framework.

The true test of any electrolysis catalyst comes when it is assembled into a working device, and here the results were particularly compelling. In a two-electrode alkaline electrolyzer with identical Ni₁Co₃@CN-sh electrodes serving as both cathode and anode, the cell required a voltage of only 1.796 volts to sustain a current density of 100 milliamperes per square centimeter. That figure outperformed a reference electrolyzer built from the noble-metal combination of platinum-on-carbon and iridium dioxide, a benchmark pairing that has defined the state of the art for decades. In the economics of water electrolysis, every hundredth of a volt saved at high current density translates directly into lower electricity consumption per kilogram of hydrogen, so an earth-abundant catalyst beating the noble-metal standard at this level is a meaningful milestone.

Perhaps the most industrially relevant finding concerns durability. Alkaline water electrolysis (AWE) is the most mature electrolysis technology, but pushing it toward industrial relevance requires operation at elevated temperatures and very high current densities—conditions that corrode, dissolve, or delaminate most laboratory catalysts within hours. The Hunan team subjected their electrolyzer to 80 degrees Celsius and a current density of 500 milliamperes per square centimeter, a regime approaching that of commercial alkaline electrolyzers. The cell held a voltage of approximately 1.84 volts for more than 200 hours of continuous operation without significant degradation. Sustained stability at 500 milliamperes per square centimeter is a demanding criterion that many highly active catalysts fail, as high current densities accelerate gas bubble formation, catalyst dissolution, and mechanical stress. Surviving this treatment suggests the carbon-supported architecture provides genuine structural resilience rather than just transient high activity.

The design strategy behind the material may prove as important as the catalyst itself. Rather than relying on complex multi-step syntheses or exotic compositions, the researchers demonstrated that systematically varying the bimetallic ratio and carbon precursor in a single pyrolysis step can systematically optimize the three-dimensional pore structure and, with it, catalytic performance. This gives the approach a clear route toward scale-up: pyrolysis of organic-metal precursors is among the simplest and most manufacturable methods for producing carbon-supported nanoparticle catalysts, and the use of nickel and cobalt—both produced in enormous quantities for batteries and steels—avoids the supply-chain fragility associated with platinum-group metals. The study also aligns with a broader trend in electrocatalysis research, where single materials must serve multiple functions, whether HER and OER in electrolyzers or the oxygen reduction and oxygen evolution reactions in rechargeable metal-air batteries.

There remain, of course, gaps between a laboratory electrode and a commercial electrolyzer stack. The researchers evaluated the catalyst on laboratory-scale electrodes in alkaline solution; industrial devices must maintain such performance over months and years, across thousands of start-stop cycles, and at even higher current densities with efficient gas separation. Faradaic efficiency, turnover frequency, and the precise identity of the active sites under operating conditions—particularly the surface species formed during OER—will require further study. The authors also note that no datasets beyond those in the paper were generated, meaning the conclusions rest on the experimental characterization presented. Still, the combination of noble-metal-matching activity, single-material bifunctionality, and demonstrated stability under elevated-temperature, high-current operation places this catalyst among the more practically oriented non-precious systems reported to date.

The work was supported by the National Natural Science Foundation of China under grant number 22379042, and the authors declare no competing interests. As governments worldwide commit to green hydrogen targets and electrolyzer manufacturing ramps up, the search for catalysts that are cheap, active, and durable intensifies. This study offers a promising answer on all three fronts: a nickel-cobalt alloy on flaky nitrogen-doped carbon that splits water as efficiently as precious metals and keeps doing so where it matters—at high current density, high temperature, and for hundreds of hours on end. If the design strategy transfers from alkaline laboratory cells to industrial electrolyzer hardware, earth-abundant catalysts of this kind could play a significant role in making hydrogen a genuinely affordable clean energy carrier.

The material, reported in National Science Review, combines a three-dimensional metallic-glass scaffold with a nickel–molybdenum nanoglass coating. Rather than treating the catalyst as a flat chemical surface, the researchers engineered its entire architecture, from the electronic environment around individual atoms to the millimeter-scale pathways through which liquids and gases move. The result is a catalytic metamaterial in which different structural levels perform different jobs, working together to improve reaction kinetics, mass transport and mechanical durability.

The foundation is a zirconium-based metallic-glass framework produced using micro-laser powder bed fusion, an additive-manufacturing technique that builds complex structures layer by layer from metallic powder. Metallic glasses lack the long-range atomic order found in conventional crystalline metals, giving them unusual combinations of strength, corrosion resistance and structural uniformity. For the scaffold, the team used triply periodic minimal surface, or TPMS, architectures. These geometries form smooth, continuously curved networks with interconnected channels, avoiding the sharp corners and dead ends that can hinder fluid movement in ordinary porous materials.

Several structures were investigated, but the Gyroid geometry offered the strongest overall balance of properties. Its continuously winding channels create a three-dimensional highway for electrolyte, while also providing escape routes for hydrogen and oxygen generated during electrolysis. The architecture can improve contact between the liquid and the catalyst without relying on narrow pores that may become blocked by gas. At the same time, the printed metallic-glass framework provides a load-bearing backbone, retaining a compressive strength above 300 megapascals according to the researchers’ measurements.

The scaffold was then covered with nickel–molybdenum amorphous particles through pulsed electrodeposition. This process produced a highly folded, flower-like coating rather than a smooth metallic film. The unusual surface morphology helps resolve one of electrolysis’s most persistent problems: the conflict between keeping the electrode wet and preventing it from becoming covered by gas. The NiMo coating is readily wetted by the alkaline electrolyte, allowing liquid to spread across the catalytic surface, but it has comparatively low affinity for gas bubbles. Bubbles can therefore detach more readily before growing large enough to mask active sites or block transport channels.

The most important chemistry, however, appears at boundaries hidden inside the nanoglass. Electron microscopy showed that the coating contains compositionally different nickel-rich and molybdenum-rich amorphous regions. These domains are joined by numerous glass–glass interfaces. Unlike grain boundaries in crystalline metals, these interfaces do not separate ordered crystal grains. Instead, they are disordered transition zones connecting two glassy regions with different compositions and local atomic arrangements. Their abundance gives the material a dense network of chemically and electronically distinct sites.

According to density-functional-theory calculations, the glass–glass interfaces modify the local electronic structure of the catalyst. The calculations indicate that these regions create more favorable conditions for hydrogen adsorption and lower the energy required for an important step in the oxygen evolution reaction. In other words, the interfaces do not merely hold the amorphous domains together; they actively influence how reactants and intermediates bind to the surface. This is significant because water electrolysis is governed not only by the number of exposed sites, but also by the precise strength with which those sites interact with hydrogen-, oxygen- and hydroxyl-containing species.

When the atomic, surface and architectural features were combined, the Gyroid-based NiMo@G electrode delivered a current density of 100 milliamperes per square centimeter at a full-cell voltage of 1.438 volts in 1-molar potassium hydroxide. Current density is a practical measure of how much electrical reaction the electrode can sustain over a given area, while the cell voltage reflects the energy required to drive the complete water-splitting process. The researchers also reported stable operation for more than 200 hours, suggesting that the mechanically reinforced scaffold and strongly integrated coating can withstand prolonged electrochemical use.

The study’s broader message is that high-performance catalysts may need to be designed less like powders and more like engineered machines. At the atomic scale, glass–glass interfaces tune reaction energetics. At the microscale, the folded NiMo surface controls wetting and bubble release. At larger scales, the Gyroid network manages electrolyte circulation, gas removal and structural loading. These functions are interdependent: faster chemistry is useful only if reactants can reach the surface, products can leave it and the electrode remains intact. By coordinating all three levels, the researchers created a catalyst that addresses reaction kinetics, mass transport and mechanical stability within one integrated platform.

The approach could be adapted beyond the specific zirconium scaffold and NiMo coating demonstrated in this study. Other metallic glasses, amorphous alloys and topology-engineered architectures may offer additional combinations of strength, conductivity, corrosion resistance and catalytic activity. The remaining challenge is to determine whether such complex structures can be manufactured economically at the scale required for industrial electrolyzers, and whether their performance will persist under higher current densities and demanding operating conditions. Even so, the work presents a striking blueprint for catalytic metamaterials: materials in which atomic interfaces, nanoscale surfaces and macroscopic flow networks are designed together to turn an electrode into a fully coordinated reaction system.

Subject of Research: Multiscale topology-engineered metallic-glass metamaterial catalysts for efficient and durable water electrolysis.

Article Title: Topology-engineered metallic-glass metamaterial catalysts with glass–glass interfaces for water splitting.

Web References: https://doi.org/10.1093/nsr/nwag442

References: National Science Review, DOI: 10.1093/nsr/nwag442.

Image Credits: © National Science Review, Congrui Yang et al.

Keywords

Water splitting, hydrogen production, electrolysis, metallic glass, nanoglass, nickel–molybdenum catalyst, Gyroid structure, metamaterial catalyst, glass–glass interfaces, additive manufacturing, bubble management, renewable energy