Effect of sulfur dioxide impurities on the electrochemical reduction of carbon dioxide over Cu-based bimetal catalysts

Electrocatalytic reduction of CO2 (CO2RR) using renewable electricity to produce value-added chemicals offers a promising way of reducing carbon emissions. Cu-based bimetals are good catalysts for the CO2RR. Industrial CO2 sources usually contain SO2 impurity gas. Understanding the effect of SO2 on the CO2 reduction performance of Cu-based bimetallic electrocatalysts is very important for developing catalysts with practical application value. Herein, the effect of SO2 on the CO2RR of Cu-based bimetallic catalysts was investigated by density functional theory (DFT). Three possible factors affecting the CO2 reduction performance of the M@Cu catalysts were studied. The results show that SO2 is easily adsorbed on the catalyst surface and reduced to S elemental substance. S adsorbed on the surface increases the overpotential of CO2 catalytic conversion. Among the ten kinds of catalysts considered, Pd@Cu shows better catalytic activity than other M@Cu catalysts. The Delta GPLS of CO2RR-to-CO increases with the rise of coverage (Theta) for the Pd@Cu catalysts after SO2 adsorption, because SO2 molecules adsorbed on the catalyst surface occupy the active sites, and increased coverage causes more active sites to be occupied. Moreover, the adsorption of intermediate species (SO4*, SO3*, and S*) on the catalyst surface increases the overpotential of the CO2RR. The formation of Cu2S affects the CO2 reduction process because the overpotential of the CO2RR on Cu2S(111) is smaller than that on Pd@Cu catalysts. These mechanistic insights can guide the rational design of SO2-resistant catalysts in the CO2 electrocatalysis field. SO2 has a significant effect on the generation of CO by CO2 electrocatalytic reaction.