Diluting the Resistance of Built‐in Electric Fields in Oxygen Vacancy‐enriched Ru/NiMoO4‐x for Enhanced Hydrogen Spillover in Alkaline Seawater Splitting

Abstract Recently, hydrogen spillover based binary (HSBB) catalysts have received widespread attention due to the sufficiently utilized reaction sites. However, the specific regulation mechanism of spillover intensity is still unclear. Herein, we have fabricated oxygen vacancies enriched Ru/NiMoO 4‐x to investigate the internal relationship between electron supply and mechanism of hydrogen spillover enhancement. The DFT calculations cooperate with in situ Raman spectrum to uncover that the H* spillover from NiMoO 4‐x to Ru. Meanwhile, oxygen vacancies weakened the electron supply from Ru to NiMoO 4‐x , which contributes to dilute the resistance of built‐in electric field (BEF) for hydrogen spillover. In addition, the higher ion concentration in electrolyte will promote the H* adsorption step obviously, which is demonstrated by in situ EIS tests. As a result, the Ru/NiMoO 4‐x exhibits a low overpotential of 206 mV at 3.0 A cm −2 , a small Tafel slope of 28.8 mV dec −1 , and an excellent durability of 550 h at the current density of 0.5 A cm −2 for HER in 1.0 M KOH seawater.