Origin and effect of surface oxygen-containing species on electrochemical CO or CO_(2) reduction reactions

Renewable-energy-powered electrochemical CO or CO_(2)reduction reactions(CO_(2)RR)provide one of the most promising strategies to upgrade CO_(2)to valuable products.In the past decade,the existence and the mechanistic role of oxygen-containing species,such as(sub)surface oxide,hydroxide and oxyhydroxide species,at the electrode–electrolyte interface under reductive conditions have emerged as a topic of acute discussion within the CO_(2)RR field.Oxide-derived Cu attracted the most attention,while other surfaces,including Au,Ag and Sn,were also widely investigated.This review identifies likely causes for contrasting results and views in the literature,summarizes possible oxygen sources for the interfacial oxygen-containing species at the CO_(2)RR conditions,and discusses potential roles these species could play in affecting the rate and product distribution.Finally,perspectives on future efforts to reveal the identity and role of oxygen-containing species in the CO_(2)RR are presented.