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

Electrocatalytic CO 2 reduction for the synthesis of high value-added multi-carbon (C 2+ ) products is a promising strategy to achieve energy storage and carbon neutrality, However, to acquire high selectivity of C 2+ products remains a challenge. Herein, Ag NCs@Ag-MOF with highly dispersed Ag nanoclusters (NCs) and Cu-O 2 N 2 -COF with Cu-O 2 N 2 active sites were designed, synthesized and then coupled for the conversion of CO 2 to liquid C 2 products (ethanol and acetate). Faradaic efficiency (FE) of the liquid C 2 products was 90.9% at -0.98 V (vs. RHE), which is 1.9 times that of Cu-O 2 N 2 -COF in direct CO 2 electroreduction and the highest liquid C 2 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 C 2 products. Ag NCs@Ag-MOF and Cu-O 2 N 2 -COF were synthesized and utilized in a tandem electrocatalytic CO 2 reduction system to significantly improve the Faradaic efficiency of liquid C 2 products (ethanol and acetate) to 90.9% with the partial current density of 120 mA cm -2 by enhanced *CO accumulation on the Cu catalyst. • Ag NCs@Ag MOF and Cu-O 2 N 2 -COF were coupled to constitute a tandem system for electrocatalytic CO 2 reduction. • Faradaic efficiency of liquid C 2 products was as high as 90.9% with the partial current density of 120 mA cm -2 . • The enhanced accumulation of *CO on the Cu catalyst significantly promoted C-C coupling and C 2 products production.