Nanoporous Bimetallic Ag–Cu Tandem Electrocatalysts for Electrochemical CO₂ Reduction to Multicarbon Products via Asymmetric C–C Coupling

Tandem catalysis represents a promising strategy to improve the selectivity toward multicarbon products in electrochemical reduction of CO2 by decoupling chemically complicated pathways into individual steps. However, it remains challenging to acquire C2+ products with high efficiency, primarily due to the sluggish kinetics of C–C coupling and the intense competition of hydrogen and C1 products. Herein, a nanoporous bimetallic Ag–Cu tandem catalyst is designed and fabricated through the electrodeposition of Cu atoms on a nanoporous Ag substrate. Via the tandem catalysis and nanostructure porous design, an efficient spillover of key intermediates (*CO) from Ag to Cu is achieved, resulting in a high Faradaic efficiency of approximately 73% for the production of C2+ products. More importantly, operando Raman and density functional theory (DFT) calculations are employed to elucidate the origins of enhanced selectivity toward ethanol, revealing the asymmetric *CHx–CO coupling mechanism due to the spillover of *CO from the Ag substrate and the selective generation of *CHx species on Cu atoms. A “dissolution–redeposition–coarsening” mechanism was proposed to govern the degradation of nanoporous Ag–Cu tandem catalysts.