Urea-Functionalized Silver Catalyst toward Efficient and Robust CO2 Electrolysis with Relieved Reliance on Alkali Cations

We report a new strategy to improve the reactivity and durability of a membrane electrode assembly (MEA)-type electrolyzer for CO2 electrolysis to CO by modifying the silver catalyst layer with urea. Our experimental and theoretical results show that mixing urea with the silver catalyst can promote electrochemical CO2 reduction (CO2R), relieve limitations of alkali cation transport from the anolyte, and mitigate salt precipitation in the gas diffusion electrode in long-term stability tests. In a 10 mM KHCO3 anolyte, the urea-modified Ag catalyst achieved CO selectivity 1.3 times better with energy efficiency 2.8-fold better than an untreated Ag catalyst, and operated stably at 100 mA cm(-2) with a faradaic efficiency for CO above 85% for 200 h. Our work provides an alternative approach to fabricating catalyst interfaces in MEAs by modifying the catalyst structure and the local reaction environment for critical electrochemical applications such as CO2 electrolysis and fuel cells.

Automated summary

We have developed a new strategy to improve the reactivity and durability of a membrane electrode assembly (MEA)-type electrolyzer for CO2 electrolysis to CO. By modifying the silver catalyst layer with urea, we have successfully promoted electrochemical CO2 reduction (CO2R), relieved limitations of alkali cation transport, and mitigated salt precipitation in the gas diffusion electrode. The urea-modified Ag catalyst exhibited significantly better CO selectivity and energy efficiency than the untreated Ag catalyst, and maintained stable performance over 200 hours. Our work provides an alternative approach to fabricating catalyst interfaces in MEAs, with important implications for CO2 electrolysis and fuel cells.