Local-reconstruction enables cobalt phosphide array with bifunctional hydrogen evolution and hydrazine oxidation

Coupling hydrazine electrooxidation with hydrogen evolution reaction (HER) attracts ever-growing attention for energy-saving H2 production. However, the performance of hydrazine-assisted HER unit is restricted by the bifunctional catalysts with un-fully activated sites. Herein, a surface local-reconstruction strategy is proposed to integrate amorphous Co(OH)2 and P vacant CoP into the CoH-CoPV@CFP catalyst. The inherent electron-deficient Co sites in Co(OH)2 show strong N-Co interaction to accelerate the N2H4 dehydrogenation kinetics, while the as-formed P vacancies in CoP play a crucial role in moderating the H* adsorption energy, the excellent bifunctionality thus being obtained. Specifically, it achieves the low overpotentials of − 77 and − 61 mV at 10 mA cm−2 for HER and HzOR in alkaline media, respectively. A lab-scale electrolyzer can deliver the industrial-grade current density of 500 mA cm−2 under ultralow cell voltage of 0.23 V. This local-reconstruction strategy may pave new avenue to design efficient catalysts for hydrazine-assisted H2 generation.