Insight into the electronic modulation on nickel-cobalt bimetallic phosphates towards high-efficiency electrocatalytic hydrogen evolution

The excessive laborious water dissociation and proton deficiency on the active sites are the major obstruction towards the industrial application of alkaline hydrogen evolution reaction (HER) electrocatalysts. Reasonably design of the catalytic configuration can flexibly adjust the electronic structure and thus enhancing their intrinsic activity. In this work, we report that the composite film NiCo(PO₄)_x coated on the nickel foam substrate (NiCo(PO₄)_x/NF) exhibits considerable activity and stability towards HER in harsh alkaline media, with an overpotential of only 68 mV to deliver 10 mA cm⁻². Also thanks to the excellent urea oxidation reaction catalytic performance, the as-constructed NiCo(PO₄)_x/NFǀǀNiCo(PO₄)_x/NF electrolyzer and an anion exchange membrane microflow electrolysis cell enable sustainable alkaline urea electrolysis for energy-saving hydrogen production. In-depth characterizations and theoretic calculations demonstrate that the coupling bimetalic sites with phosphate unit creats appropriate metal-oxygen 3d-2p orbital hybridization state, thereby enhancing the HER kinetics comprehensively, including water dissociation and proton adsorption/desorption. This work brought forth a cost-effective and self-supporting metallic-phosphate electrocatalyst for efficient hydrogen evolution.