Hydrogen Generation from Seawater Electrolysis over a Sandwich-like NiCoN|Ni_xP|NiCoN Microsheet Array Catalyst

Seawater electrolysis presents a transformative technology for sustainable hydrogen production and environmental remediation. However, the lack of active and robust hydrogen evolution reaction (HER) catalysts severely impedes the development of this technology. Here, we report a sandwich-like nanostructured HER catalyst constructed by decorating both sides of nickel phosphide (NixP) microsheet arrays with nickel cobalt nitride (NiCoN) nanoparticles. The resulting integrated hierarchical sandwich-like catalyst (NiCoN|NixP|NiCoN) simultaneously provides a large surface area with abundant active sites, improved intrinsic activity of every active site, and high electrical conductivity for efficient charge transfer. Consequently, the NiCoN|NixP|NiCoN electrode exhibits very good HER activity, requiring a small overpotential of 165 mV to achieve a current density of 10 mA cm–2 in natural seawater electrolyte, along with very impressive stability benefiting from the good chlorine-corrosion resistance of the inner NixP microsheet arrays. Our work paves a new route toward the design of hierarchical nonprecious catalysts for hydrogen generation from seawater electrolysis.