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

Abstract

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 ΔG_PLS of CO₂RR-to-CO increases with the rise of coverage (Θ) 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.