Gaseous oxidation-reduction derived vacancy-rich nanoporous nickel: Boosting phosphidation for high-performance bifunctional water-splitting electrodes

Developing a low-cost, robust bifunctional electrode is critical for alkaline water electrolysis. Herein, a vacancy-rich nanoporous Ni (PNF) is fabricated via a gaseous oxidation-reduction strategy, acting as a highly reactive precursor for the phosphidation to form a nanorod-structured Ni₂P/PNF electrode. This well-designed hierarchical architecture not only maximizes the exposure of electrocatalytic active sites but also significantly accelerates the surface reconstruction of oxygen evolution reaction (OER) toward the formation of highly active NiOOH species. As a result, it delivers an ultralow overpotential of 270 mV at 10 mA cm−2 for OER, which is merely one-third of the electrode adopting bare Ni foam as the precursor, and outperforms the majority of reported state-of-the-art Ni₂P-based electrodes. Moreover, benefiting from the optimized hydrogen adsorption free energy induced by Ni vacancies and phosphorus doping, the as-prepared electrode also exhibits enhanced hydrogen evolution reaction (HER) activity, demonstrating its outstanding bifunctional performance for overall water splitting.