Electron Back-Donation at the Pt Cluster/Fe–N4 Interface as an Adaptive Dynamic Electronic Switch for Hydrogen Evolution Kinetics

Abstract Support substrates are conventionally designed to spatially confine Pt clusters in terms of size and mobility, while the dynamic evolution of interfacial chemical bonds during catalysis has often been selectively overlooked owing to its complexity. However, interfacial electron flow fundamentally determines the overall catalytic activity. Herein, employing constant-potential ab-initio molecular dynamics simulations (CP-AIMD), we systematically explore the hydrogen evolution reaction (HER) kinetics of Pt clusters anchored on a Fe–N4 substrate. Our analysis reveals that the interfacial Pt–Fe bond functions as a dynamic electronic switch, adapting to the catalytic environment and governing HER activity. Specifically, upon electron depletion at the Pt site, the Pt–Fe bond spontaneously breaks, triggering electron back-donation to Pt d orbitals. This continuously optimizes the electronic configuration to dynamically meet the adsorption demands of reactive species. Crucially, Pt–Fe bond breaking and restoring open a low-barrier HER pathway, which progressively dominates competing pathways under loading potential. Screening various single-atom substrates identifies the electronegativity difference between Pt and the metal single-atom as a key descriptor dictating the electron back‑donation behavior. Our findings unveil a functional shift of interfacial chemical bonds from passive structural anchors to active electronic regulators, establishing a strategy for the rational design of supported metal cluster catalysts.