Bimodal Nanoporous Cu–Pd Alloys Decorated with Ag Nanoparticle for Selective Electrochemical CO2 Reduction to Methane

Abstract Copper-based catalysts uniquely drive the electrochemical CO2 reduction reaction (CO2RR) to value-added hydrocarbons, but poor product selectivity, inadequate stability, and mass-transfer limitations at high current densities restrict their practical application. Herein, a structure–composition synergistic regulation strategy was proposed to fabricate a bimodal nanoporous CuPd–Ag tandem catalyst via nanoporous engineering and bimetallic alloying. By tailoring the bimodal nanoporous morphology and tandem heterointerfaces, the optimized catalyst exhibits remarkable CO2-to-CH4 conversion performance, achieving a CH4 Faradaic efficiency of 58.3% and a total current density of 230 mA cm–2. Operando Raman spectroscopy and DFT-calculated free energy profiles reveal a dual-promotion tandem mechanism: *CO intermediates from CO2 activation on Ag sites rapidly spill over to adjacent Cu–Pd sites to build a high-concentration *CO microenvironment, while adsorbed *H on Pd atoms in the Cu–Pd alloy lattice facilitates the rate-determining *CO hydrogenation to *CHO, thus accelerating selective CH4 evolution. The deactivation during long-term operation was also elucidated. Under cathodic polarization, the catalyst underwent surface structural reconstruction, Cu and Ag dissolution, and subsequent collapse of the porous framework, collectively leading to deactivation. This work establishes the structure–activity relationship of tandem configurations, providing theoretical insights for designing highly selective and stable CO2RR electrocatalysts toward practical CO2 utilization.