Dynamic Structural Evolution of Single-Atom Catalysts at the Catalyst–Electrolyte Interface: Insights from Electrochemical Coupled Field

Dynamic catalytic structures at the catalyst-electrolyte interface pose significant challenges in accurately identifying active sites and establishing precise structure-activity relationships essential for catalyst design and performance optimization. Herein, we unveil the dynamic structural evolution of Cu-N-C single-atom catalysts (SACs) under electrochemical conditions, elucidating the critical role of the electrochemical coupled field. Using hybrid-solvation constant potential simulations, we identify that the unique <i>d</i>_{<i>x</i>2-<i>y</i>2} orbital occupancy at the Fermi level, stemming from copper's <i>d</i>⁹ electronic configuration, renders Cu-N bonds highly sensitive to external voltage. Proton transfer (PT) triggers electronic reordering that converts discrete energy levels into continuous states near the Fermi level, enhancing charge accumulation in the Cu-N antibonding state. Consequently, the Cu-N bonds are weakened, ultimately leading to copper atom leaching. Our work provides a fundamental understanding of SACs' dynamics under realistic electrochemical environments, offering new insights for the rational design of robust electrocatalysts.