Mass Transport-Dependent C–C Bond Formation for CO Electroreduction with Alkali Cations
Yan Wen, Tiantian Wu, Jia Liu, Zhe Zheng, Ming Ma
Abstract
Electrolyte cation identity has been reported to influence the multicarbon (C 2+ ) selectivity in CO 2 /CO electroreduction. However, most of the previous work for cation size effect is based on H-cell configurations, which may inadvertently distort the underlying mechanism of cation effect due to mass transport limitations, particularly for CO reduction. Here, using GDE-type flow electrolyzers, we report that the selectivity of total C 2+ products on Cu is independent of alkali cation identity (Li +, Na +, K +, and Cs + ) in the absence of the CO transport limitation. Notably, a high concentration of strongly hydrated cation (such as Li + ) inhibits the total C 2+ formation in CO reduction, whereas total C 2+ selectivity is retained upon increasing concentrations of weakly hydrated cation (such as K + ). Further investigations reveal that the CO coverage at a low cation concentration is almost independent of the cation identity, but the CO coverage at highly concentrated cations strongly relies on the alkali cation identity.