Facile fabrication of Sn/SnOx electrode as an efficient electrocatalyst for CO2 reduction to formate

Abstract

Producing valuable hydrocarbons via electrochemical reduction of CO2 has been a promising active research area. In this study, it was aimed to develop a low-cost and efficient Sn-based electrode reducing CO2 to formate with high selectivity. SnOx thin-film electrode was prepared via potentiostatic electrodeposition at the potentials of -0.5 V, -0.6 V, -0.7 V, and -0.8 V vs. Ag/AgCl on a pure Sn plate for 300 s in an acidic media. The Sn/SnOx electrode which was prepared at -0.6 V was found to have the highest Faradaic efficiency. Electrochemical reduction of CO2 was carried out on this Sn/SnOx electrode in aqueous CO2-saturated 0.1 M KHCO3 solution. The optimum values for the parameters which have significant impacts on Faradaic efficiency for producing formate namely, electrolysis potential and electrolysis time were determined. The maximum Faradaic efficiency of formate on the Sn/SnOx electrode was obtained as 74.7 % at the applied potential of -1.8 V in an H-type cell. The maximum Faradaic efficiency of formate obtained on the Sn/SnOx electrode reached about twice the value obtained on the Sn plate (39.7 %). The results also indicated that the Sn/SnOx electrode has higher catalytic stability and electrochemically active surface area (2.08 cm2) than the bare Sn plate (0.82 cm2). This study showed that an efficient Sn/SnOx electrode can be developed with a simple method that involves only a SnSO4/ H2SO4 solution and as short as 300 s plating duration via electrodeposition at a lower overpotential of -0.6 V. The novelty of this study can be attributed to the combination of simple and unique electrocatalyst preparation procedure with less energy consumption and chemical/additive use, short deposition time, and relatively low overpotential for developing an efficient Sn/SnOx electrocatalyst ensuring a high Faradaic efficiency for formate production. Thus, producing formate from the conversion of CO2 which is a waste carbon source, was achieved by a quite simple and economic method.