Revisiting Catalyst Restructuring in CO 2 Reduction: The Dominant Yet Overlooked Role of Hydrogen

reduction, a *H-activated mechanism is proposed, in which the ever-present but largely overlooked adsorbed *H acts as the dominant driving force. Rather than the *CO or the applied potential alone, *H induces pronounced Cu-Cu bond weakening and lattice expansion across the entire electrochemical potential window, creating a *H-activated lattice state. This preconditioned state enables intermediates such as *COOH or *CO to trigger structural restructuring with low leaching barriers even down to 0.29 eV. More importantly, this mechanism successfully predicts the restructuring tendency and electrochemical stability of other metals, including Au, Ag, Pt, Ni, and Ir, aligning well with experimental observations. Therefore, these findings unify previously fragmented mechanistic perspectives on the dynamic evolution of the catalyst structure, offering a robust foundation for designing catalysts with both high activity and stability.