Industrial-scale efficient alkaline water electrolysis achieved with sputtered NiFeV-oxide thin film electrodes for green hydrogen production

We propose a magnetron sputtering technique to enhance HER and OER performance with a bifunctional vanadium-substituted NiFe-based catalyst electrode formed into a NiFeV-oxide thin film. The sputtering approach generates oxygen vacancies by creating nonstoichiometric oxidation phases, i.e., Fe₃O_4−x and VO_2−y. Operando Raman spectroscopy reveals a synergistic effect between active metal sites and oxygen vacancies to promote the formation of a reconstructed active layer, i.e., NiFe(oxy)hydroxyl, during anodic oxidation. This phase transition optimizes the adsorption energy of water intermediates to accelerate the water splitting. Moreover, the leaching of vanadium also plays a vital role in the activation and surface restructuring processes of the NiFeV-oxide pre-catalyst during OER electrocatalysis. Feasibility studies for an NFV-0.7(−)‖NFV-0.7(+) stack-cell electrolyzer indicate that it delivers a high current density of 1000 mA cm⁻² at low cell potentials of 2.00 V (without cell heating) and 1.84 V (at 60 °C) and exhibits excellent stability at 1000 mA cm⁻² over 100 h. Our work offers a new paradigm for designing efficient bifunctional electrocatalysts, holding great promise for industrial-scale water splitting.