Highly selective electrocatalytic CO₂ reduction to liquid C₂ products by means of a tandem catalytic system

Electrocatalytic CO₂ reduction for the synthesis of high value-added multi-carbon (C₂₊) products is a promising strategy to achieve energy storage and carbon neutrality, However, to acquire high selectivity of C₂₊ products remains a challenge. Herein, Ag NCs@Ag-MOF with highly dispersed Ag nanoclusters (NCs) and Cu-O₂N₂-COF with Cu-O₂N₂ active sites were designed, synthesized and then coupled for the conversion of CO₂ to liquid C₂ products (ethanol and acetate). Faradaic efficiency (FE) of the liquid C₂ products was 90.9% at -0.98 V (vs. RHE), which is 1.9 times that of Cu-O₂N₂-COF in direct CO₂ electroreduction and the highest liquid C₂ products selectivity reported so far. The current density reached 324.8 mA cm^-2 at -1.2 V (vs. RHE). In situ infrared spectroscopy and density functional theory calculations showed that the tandem catalytic system significantly enhanced the accumulation of ^*CO on the catalyst and promoted ^*CO-^*CO coupling, thus significantly improving the selectivity of liquid C₂ products.