Engineering Low-Cost NiFeMo Bifunctional Catalyst into High-Performance Superaerophobic Nanoarray Electrode for Water and Seawater Electrolysis at Industrial-Scale Current Density

Abstract

Hydrogen is produced cleanly through water electrolysis, comprising hydrogen and oxygen evolution reactions (HER and OER). However, expensive catalysts and their complex fabrication processes are significant barriers to the commercialization of the technology. In this study, we report a cost-effective, industrially scalable two-step method of engineering a high-performance bifunctional catalytic electrode based on earth-abundant transition metals for both HER and OER. NiMoO_x was first prepared via electrodeposition of Ni and Mo on a Ni foam or fiber paper; subsequently, a porous NiFeOOH thin layer was synthesized via in situ growth on top. Benefiting from having multiple active sites, low charge transfer resistance, and a hydrophilic and superareophobic nanoarray surface that facilitates electrolyte diffusion and rapid gas bubble release, the as-prepared NiFeOOH/NiMoO_x electrode demonstrated outstanding bifunctional HER and OER activities and good durability, tested in both half-cells and flow-type alkaline water/seawater electrolyzers, which achieved an industrial scale current density of 2 A cm⁻² with a low voltage of 2.19 V/2.37 V.