Promoting Water Dissociation and Weakening Active Hydrogen Adsorption to Boost the Hydrogen Transfer Reaction over a Cu−Ag Superlattice Electrocatalyst

Abstract The prerequisite for electrocatalytic hydrogenation reactions (EHRs) is H 2 O splitting to form surface hydrogen species (*H), which occupy catalytic sites and lead to mismatched coverage of *H and reactants, resulting in unsatisfactory activity and selectivity. Thus, modulating the splitting pathway of H 2 O is significant for optimizing the EHR process. Herein, a Cu−Ag alloy with a superlattice structure of staggered‐ordered Cu and Ag is theoretically predicted and experimentally proven to undergo a pathway for H 2 O splitting called the hydrogen transfer reaction (HTR) in the water layer, which involves the formation of *H, the capture of *H by a water cluster to form H*(H 2 O) x and subsequent hydrogenation reactions by H*(H 2 O) x . Taking acetylene hydrogenation as a model case, the as‐proposed HTR pathway could lead to a relaxation hydrogenation process to modulate the matching degree of C 2 H 2 and *H, thus enabling a 91.2 % C 2 H 4 Faradaic efficiency at a partial current density of 0.38 A cm −2 , greatly outperforming its counterpart without a superlattice structure.