Oxyhydroxide Species Enhances CO2 Electroreduction to CO on Ag via Coelectrolysis with O2

Ag and Au are efficient monometallic electrocatalysts for the CO2 reduction reaction (CO2RR) to CO. Recent preoxidation treatments on Ag and Au have been shown to effectively improve their reactivity in CO production. However, the mechanism underlying the improvements remains controversial. The challenges in probing the surface speciation under reaction conditions hinder the efforts to be made for correlating the catalyst surface speciation with its performance. Herein, we combine in situ surface-enhanced Raman spectroscopy and reactivity measurements to investigate the coelectrolysis of CO2 and O2 demonstrating that the in-situ-formed surface oxyhydroxyl species on Ag can significantly enhance the CO production rate (>80 fold). In contrast, no surface oxyhydroxyl species was observed on Au in coelectrolysis with O2, which was accompanied by much less significant enhancement in the CO activity (<3-fold). Our work highlights the impact of catalyst surface speciation on the CO2RR performance and opens up a promising route for designing efficient CO2RR catalysts. We believe the findings presented in our work point out a fruitful strategy to design an advanced catalyst and reaction scheme to achieve efficient CO2RR.