Ampere-Level Acetylene-to-Ethylene Electrosynthesis by a Spillover-Storage-Relaxation Hydrogenation Mechanism to Overcome the Activity-Selectivity Constraint

The scaling relationship between the activity and selectivity of electrocatalytic hydrogenation reactions (EHRs) is caused by severe hydrogen evolution reactions and overhydrogenation because of the inevitable blocking of active sites through excessive adsorbed hydrogen (*H) at high current density. Herein, a spillover–storage–relaxation hydrogenation mechanism is proposed to overcome the scaling relationship. By employing acetylene (C 2 H 2 ) to ethylene (C 2 H 4 ) conversion as an example, Cu-supported atomically dispersed WO x (WO x /Cu), with abundant interfacial *H-formation Cu and *H-reservoir WO x sites, is theoretically predicted and experimentally proven to be a promising catalyst. Consequently, WO x /Cu is synthesized and demonstrates a C 2 H 4 partial current density of ∼1.43 A cm –2, with a C 2 H 4 Faradaic efficiency higher than 95%. The *H transfer from Cu to WO x not only frees sites for C 2 H 2 adsorption but also reserves a hydrogen source for subsequent hydrogenation. Additionally, such a mechanism is suitable for Mo(W)O x /Cu(Ag) in other EHRs.