Effect of Halide Anions on Electrochemical CO Reduction in Non-Aqueous Choline Solutions using Ag and Au Electrodes.

In this study, the effect of halide anions on the selectivity of the CO reduction reaction to CO was investigated in choline-based ethylene glycol solutions containing different halides (ChCl : EG, ChBr : EG, ChI : EG). The CORR was studied using silver (Ag) and gold (Au) electrodes in a compact H-cell. Our findings reveal that chloride effectively suppresses the hydrogen evolution reaction and enhances the selectivity of carbon monoxide production on both Ag and Au electrodes, with relatively high selectivity values of 84 % and 62 %, respectively. Additionally, the effect of varying ethylene glycol content in the choline chloride-containing electrolyte (ChCl : EG 1 : X, X=2, 3, 4) was investigated to improve the current density during CORR on the Ag electrode. We observed that a mole ratio of 1 : 4 exhibited the highest current density with a comparable faradaic efficiency toward CO. Notably, an evident surface reconstruction process took place on the Ag surface in the presence of Cl ions, whereas on Au, this phenomenon was less pronounced. Overall, this study provides new insights into anion-induced surface restructuring of Ag and Au electrodes during CORR, and its consequences on the reduction performance on such surfaces in non-aqueous electrolytes.