SO₂‑Induced Selectivity Change in\nCO₂ Electroreduction

Abstract

Electrochemical conversion\nof carbon dioxide (CO₂) to\nvalue-added chemicals has attracted much attention in recent years\nas a potential alternative to fossil resources. Although significant\nworks have studied the influence of impurities in the electrolyte\n(e.g., metal ions), few studies have been performed to understand\nthe influence of gaseous impurities in CO₂ electroreduction.\nHerein, we study the effects of sulfur dioxide (SO₂) on\nAg-, Sn-, and Cu-catalyzed CO₂ electrolysis in a flow-cell\nelectrolyzer in near-neutral electrolyte, representing a broad range\nof CO₂ reduction catalysts. We show that the presence of\nSO₂ impurity reduces the efficiency of converting CO₂ due to the preferential reduction of SO₂. In the\ncases of Ag and Sn, the effect of SO₂ impurity was reversible\nand the catalytic activities of both catalysts were recovered. On\nthe contrary, a shift in selectivity toward formate accompanied by\na suppression of multicarbon (C₂₊) products was observed\non Cu catalyst, demonstrating that Cu is highly sensitive to SO₂ impurity. Our results suggest that CO₂ obtained\nfrom direct air capture technologies or biorefineries could be more\nsuitable for Cu-catalyzed CO₂ electrolysis as these CO₂ sources would be relatively cleaner (SO₂-free)\nthan fossil-derived sources such as power plants and can be directly\ncoupled with distributed renewable energy sources such as wind and\nsolar.