Dynamic Phase‐Evolution‐Triggered Strong Metal‐Support Interaction Configures Atomic Ru Sites for Superior Alkaline Hydrogen Evolution

ABSTRACT Phase engineering effectively modulates the strong metal‐support interaction (MSI) in heterogeneous catalysts. However, the dynamic manipulation of MSI through in situ phase transition remains underexplored. Herein, an acid‐mediated strategy for in situ 1T→2H phase transformed MoSe 2 has been reported to construct Ru sites (Ru‐2H(PT)‐MoSe 2 /CC) toward alkaline hydrogen evolution reaction, in contrast to direct Ru sites construction on the static 2H‐phase MoSe 2 (Ru‐2H‐MoSe 2 /CC). X‐ray photoelectron spectroscopy demonstrates that, despite both catalysts sharing the same 2H‐phase structure, the phase‐evolved Ru‐2H(PT)‐MoSe 2 /CC exhibits significant electron accumulation at Mo and Se sites, enabling strong electrostatic interaction with the Ru 3+ precursor, which dictates the final atomic configuration of Ru. Combined theoretical and experimental studies demonstrate that this strong MSI preferentially stabilizes Ru as single atoms at Mo sites concurrently with the formation of smaller Ru clusters. In stark contrast, the weak MSI in Ru‐2H‐MoSe 2 /CC leads to the predominant formation of larger Ru clusters. The resultant Ru‐2H(PT)‐MoSe 2 /CC yields a low overpotential of 26 mV at 10 mA cm −2 and long‐term durability for 500 h at 100 mA cm −2 . In situ Raman spectroscopy and theoretical calculations further corroborate that the unique Ru configuration optimizes interfacial water behavior and accelerates water dissociation kinetics.