CrO_x Modified Nickel Phosphides Electrocatalyst for Stable Hydrogen Evolution Reaction in Neutral Media

Abstract The development of efficient and long‐term stable electrodes for hydrogen evolution reaction (HER) in seawater is highly desirable for hydrogen generation but remains challenging. In this work, a highly active CrO_x@Ni₂P‐Ni₅P₄/NF electrode is developed and investigated its dynamic reconstruction for HER in neutral electrolytes. The combination of in situ Raman spectra and electrochemical measurements revealed the dynamic surface reconstruction of the catalyst during HER. The CrO_x modification not only effectively facilitates water dissociation but also stabilizes the structure post‐reconstruction, enabling rapid and stable hydrogen generation in neutral media. Remarkably, CrO_x@Ni₂P‐Ni₅P₄/NF exhibits overpotentials of 109 and 263 mV at current densities of 10 and 100 mA cm⁻² in 1 m PBS, respectively. Concurrently, it exhibits stable operation for 500 h in 1 m PBS and 140 h in natural seawater at current densities of 50 and 100 mA cm⁻², respectively. The proposed catalytic electrode and the mechanistic insights present a significant stride toward the realization of metal phosphides for direct seawater splitting.