Electrocatalytic CO2 Reduction over Sn-Cu Bimetallic Catalysts Synthesized via an Amalgamated Lithium Metal Method.

Electrochemical carbon dioxide reduction reaction (eCO2RR) provides a pathway to convert CO2 into value-added chemicals. Here, we report a family of carbon-supported tin-copper (Sn-Cu) bimetallic catalysts synthesized via an amalgamated lithium metal (ALM) method with controlled tuning of metal dispersion from isolated atoms to nanocrystallites. As metal loadings increase, the catalyst structure evolves from atomically dispersed Sn-Cu dual sites (Sn1.5Cu/C-0.75) to Sn-rich nanodomains (Sn3Cu/C-13) and Cu/Sn crystallites (Sn3Cu/C-24), leading to a systematic shift in CO2RR selectivity from acetaldehyde to formate at low overpotentials. Notably, Sn1.5Cu/C-0.75 achieves a Faradaic efficiency of 49.7% for acetaldehyde at -0.5 V versus the reversible hydrogen electrode. The CO2 conversion pathways behind these selective, size-modulated catalysts are elucidated by structural characterization, together with electrochemical analysis of structure-selectivity correlations, establishing a clear structure-property relationship for tuning CO2RR pathways.