A 17.73% Solar‐to‐hydrogen Efficiency with Durably Active Catalyst in Stable Photovoltaic‐electrolysis Seawater System

Developing durably active catalysts to tackle harsh voltage polarization and seawater corrosion is pivotal for efficient solar‐to‐hydrogen (STH) conversion, yet remains a challenge. We report a durably active catalyst of NiCr‐layered double hydroxide (RuldsNiCr‐LDH) with highly exposed Ni‐O‐Ru units, in which low‐loading Ru (0.32 wt%) is locked precisely at defect lattice site (Rulds) by Ni and Cr. The Cr site electron equilibrium reservoir and Cl‐ repulsion by intercalated CO32‐ ensure the highly durable activity of Ni‐O‐Ru units. The RuldsNiCr‐LDH‖RuldsNiCr‐LDH electrolyzer based on anion exchange membrane water electrolysis (AEM‐WE) shows ultrastable seawater electrolysis at 1000 mA cm‐2. Employing RuldsNiCr‐LDH both as anode and cathode, a photovoltaic‐electrolysis seawater system achieves a 17.73% STH efficiency, corresponding photoelectricity‐to‐hydrogen (PVTH) efficiency is 72.37%. Further, we elucidate the dynamic evolutionary mechanism involving the interfacial water dissociation‐oxidation, establishing the correlation between the dynamic behavior of interfacial water with the kinetics, activity of RuldsNiCr‐LDH catalytic water electrolysis. Our work is a breakthrough step for achieving economically scalable production of green hydrogen.