Oxygen vacancy mediated and enhanced metal-P bonds for stabilizing reconstruction for alkaline freshwater and seawater electrolysis†

The performance of electrochemical water splitting can be effectively enhanced by preventing irreversible structural distortion that leads to the leaching of active elements. In this study, a porous grass-shaped Fe₂P/Ni₅P₄-Ov catalyst was synthesized using oxygen vacancies (Ov), exhibiting robust M–P bonds. Both experimental and theoretical investigations show that these strong M–P bonds play a crucial role in stabilizing electrochemical transformation of the precursor catalyst to active Ni, Fe-(oxy)hydroxide species, thereby reducing Fe loss. Additionally, the enhanced orbital coupling weakens the OH–H bonds in the H₂O molecule. Remarkably, Fe₂P/Ni₅P₄-Ov demonstrates exceptional OER and HER activity and stability in both alkaline freshwater and seawater solutions by preventing the leaching of Fe elements. This research underscores the transition from metal–organic frameworks to the evolution of metal oxides into metal phosphides and offers insights into inhibiting the leaching of active elements.