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.