An experimental study of electroreduction of CO2 to HCOOH on SnO2/C in presence of alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) and anions (HCO3−, Cl−, Br− and I−)

It is well-known that the electrolytes can influence the electrochemical reduction of carbon dioxide (ERCO2) in aqueous media. In this work, we explore the effects of alkali metal cations and anions (Li+, Na+, K+, Rb+, Cs+, HCO3−, Cl−, Br−, I−) on the current density and product selectivity for the ERCO2 into formic acid (HCOOH) on the SnO2/carbon paper (SnO2/C) electrode. Results of the ERCO2 experiments show that for the cations, the promotion effects on current density and faradaic efficiencies (FEs) are in the order of Li+ < Na+ < K+ < Cs+ < Rb+. For the anions, the current density values are in the order of NaHCO3 < NaCl < NaBr < NaI and KHCO3 < KCl ≈ KI < KBr, respectively, and that on the FEs for the formation of the HCOOH (FEHCOOH) is HCO3− < Cl− < Br− < I−. Based on this result, the effects of alkali metal cations and anions on ERCO2 are discussed.