Partial Amorphization of Proton‐Conducting Perovskites Triggers Interfacial Water Optimization to Boost Proton Transfer Kinetics for PEM Electrolysis

ABSTRACT Modulating the interfacial water structure at the catalyst‐electrolyte interface and optimizing the hydrogen adsorption/desorption kinetics of ruthenium‐based electrocatalysts are essential for hydrogen evolution reaction (HER), yet these remain significant challenges. Herein, we propose a hybrid catalyst ac‐Ru/BaZr _0.1 Ce _0.7 Y _0.1 Yb _0.1 O _3‐δ ‐C (ac‐Ru/BZCYYb‐C), featuring an amorphous/crystalline substrate fabricated via an in situ electrochemical reconstruction strategy. Comprehensive in situ Raman and electrochemical investigations reveal that partial amorphization of the proton‐conducting perovskite BZCYYb optimizes the interfacial water structure. This reconstruction promotes the conversion of 4‐coordinated hydrogen‐bonded water (4‐HB‐H ₂ O) into free‐H ₂ O and 2‐HB‐H ₂ O. Such optimized interfacial water structure improves the hydrogen adsorption/desorption kinetics on Ru sites, thus promoting HER kinetics. Consequently, the ac‐Ru/BZCYYb‐C catalyst demonstrates excellent acidic HER activity, requiring an overpotential of only 17 mV to deliver −10 mA cm ⁻² and showing remarkable long‐term durability for 200 h with negligible degradation. Moreover, PEMWE cell employing ac‐Ru/BZCYYb‐C as the cathode catalyst achieves 2 A cm ⁻² at only 1.84 V and maintains outstanding stability over 150 h in pure water at 2 A cm ⁻² .