From Glass Interfaces to 3D Flow Networks: Engineering Catalysts Across Scales

Water splitting is often described as a simple recipe: apply electricity to water, and hydrogen and oxygen emerge. In practice, building an electrode that can sustain this reaction efficiently is far more complicated. A working water-splitting electrode must accelerate chemical reactions, deliver electrolyte to active sites, remove hydrogen and oxygen bubbles, conduct electricity, tolerate mechanical stress and remain stable for hundreds or thousands of hours. Researchers at Songshan Lake Materials Laboratory have now addressed these competing demands by designing a catalyst as a coordinated system that operates across atomic, microscopic and macroscopic length scales.

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.

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

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

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