The Role of Phosphorus on Alkaline Hydrogen Oxidation Electrocatalysis for Ruthenium Phosphides

Abstract Transition metal/p‐block compounds are regarded as the most essential materials for electrochemical energy converting systems involving various electrocatalysis. Understanding the role of p‐block element on the interaction of key intermediates and interfacial water molecule orientation at the polarized catalyst‐electrolyte interface during the electrocatalysis is important for rational designing advanced p‐block modified metal electrocatalysts. Herein, taking a sequence of ruthenium phosphides (including Ru 2 P, RuP and RuP 2 ) as model catalysts, we establish a volcanic‐relation between P‐proportion and alkaline hydrogen oxidation reaction (HOR) activity. The dominant role of P for regulating hydroxyl binding energy is validated by active sites poisoning experiments, pH‐dependent infection‐point behavior, in situ surface enhanced infrared absorption spectroscopy, and density functional theory calculations, in which P could tailor the d‐band structure of Ru, optimize the hydroxyl adsorption sites across the Ru−P moieties, thereby leading to improved proportion of strongly hydrogen‐bonded water and facilitated proton‐coupled electron transfer process, which are responsible for the enhanced alkaline HOR performance.