Enhanced Electrochemical Reduction of CO2 to CO on Ag/SnO2 by a Synergistic Effect of Morphology and Structural Defects.

Silver (Ag)-based materials are considered to be promising materials for electrochemical reduction of CO2 to produce CO, but the selectivity and efficiency of traditional polycrystalline Ag materials are insufficient; there still exists a great challenge to explore novel modified Ag based materials. Herein, a nanocomposite of Ag and SnO2 (Ag/SnO2 ) for efficient reduction of CO2 to CO is reported. HRTEM and XRD patterns clearly demonstrated the lattice destruction of Ag and the amorphous SnO2 in the Ag/SnO2 nanocomposite. Electrochemical tests indicated the nanocomposite containing 15% SnO2 possesses highest catalytic selectivity featured by a CO faradaic efficiency (FE) of 99.2% at -0.9 V versus reversible hydrogen electrode (vs RHE) and FE>90% for the CO product at a wide potential range from -0.8 V to -1.4 V vs RHE. Experimental characterization and analysis showed that the high catalytic performance is attributed to not only the branched morphology of Ag/SnO2 nanocomposites (NCs), which endows the maximum exposure of active sites, but also the special adsorption capacity of abundant defect sites in the crystal for *COOH (the key intermediate of CO formation), which improves the intrinsic activity of the catalyst. But equally important, the existed SnO2 also plays an important role in inhibiting hydrogen evolution reaction (HER) and anchoring defect sites. This work demonstrates the use of crystal defect engineering and synergy in composite to improve the efficiency of electrocatalytic CO2 reduction reaction (CO2 RR).