Active site concentration steers the reaction pathway of CO2 electroreduction

Abstract

Critical influence of local active-site concentration and configuration on CO₂ reduction selectivity remains rarely explored, due to the challenge in constructing well-defined structures. In this study, we employ a molten salt-assisted strategy to synthesize Ce-O_V-Cu cascade catalyst with tunable configurations and relative concentrations of Cu and Ce-O_V sites. Two distinct geometries were constructed: one featuring dense Cu sites surrounding Ce-O_V, and another with isolated Cu centers encapsulated by Ce-O_V. These configurations effectively direct the key *CHO or *COH intermediates toward either coupling with *CO or hydrogenation with *H, thereby switching product selectivity. The CuCe₁₀O_x catalyst with isolated copper centers achieves a high CH₄ Faradaic efficiency (FE) of 61.7% at −1.6 V vs. reversible hydrogen electrode (RHE), whereas the local Cu-rich Cu₁₀CeO_x variant favors C₂ production with a maximum FE of 61.5% at −1.4 V vs. RHE. Mechanistic studies reveal that locally concentrated Cu sites exhibit strong *CO₂ binding affinity, enhancing *CO surface coverage and facilitating *CO–*COH coupling; while Ce-O_V-rich regions with isolated copper center supply abundant availability *H, promoting deep protonation of *CHO intermediate toward CH₄. This work offers valuable insights into catalyst design, where manipulating structural chemistry guides catalytic processes toward targeted CO₂RR products.