Anomalous pH‐Dependence of Ru for Hydrogen Electrochemistry

Abstract The essence of the classic pH‐dependent catalytic behavior of Pt toward hydrogen electrochemistry has been debated for decades. In stark contrast, Ru represents a unique exception by exhibiting intrinsically anomalous pH dependence among Pt‐group metals, significantly challenging the universal validity of the existing mechanistic system derived from classic pH effects. To decode the chemical essence beneath the unique anomalous pH dependence, refined multidimensional structural characterizations and electrical transport spectroscopic studies reveal that the electron delocalization on Ru surface enables strong oxophilicity and unique pH‐dependent coverage of OH*, essentially different from the H*‐dominated Pt surface. The enriched OH* breaks the classic pH‐dependent rule by forming hydrogen bond‐regulated interfacial water structures, thus creating a unique chemical environment for alkaline hydrogen catalysis. By clearly decoding the anomalous pH‐dependent behavior of Ru, our work provides new chances to improve the physicochemical model for re‐understanding hydrogen electrochemistry.