Polymorphism‐Interface‐Induced Work Function Regulating on Ru Nanocatalyst for Enhanced Alkaline Hydrogen Oxidation Reaction

Abstract Exploring high‐performance Pt‐free electrocatalysts for hydrogen oxidation reaction (HOR) in alkaline media is highly imperative for the development of alkaline polymer electrolyte fuel cells. Phase engineering is an effective strategy for boosting the catalytic performance of electrocatalysts; however, the fabrication of unconventional polymorphism‐interfaced metal catalysts remains a significant challenge. In this study, a polymorphism‐interfaced Ru nanocatalyst with a stable hexagonal close‐packed (hcp) phase and a metastableface‐centered‐cubic (fcc) phase is successfully prepared. Owing to the built‐in electric field and stacking fault on the unique polymorphic interface, the fcc‐hcp‐Ru catalyst exhibits outstanding alkaline HOR performance with a mass activity of 1016 A g_PGM^‐1, which is six and three times higher than that of conventional hcp‐Ru andcommercial Pt/C, respectively. The regulated electron distribution at the polymorphic interface is attributed to the discrepant work functions, which not only optimize the adsorption energy of hydrogen but also facilitate the water formation step to promote the alkaline HOR process. This study demonstrates that unconventional polymorphism‐interfaced engineering is an efficient strategy to regulate the electronic structure of metal catalysts and identifies the prominent role of the work function in alkaline HORs, providing a new avenue for the rational design of highly efficient materials for electrocatalysis.