In-situ Analysis of CO2 Electroreduction on Pt and Pt Oxide Cathodes

The issue of excessive amounts of CO2 in the atmosphere has promoted the study of methods of removing it from the atmosphere. In the field of electrochemistry, electroreduction of CO2 has become an area of significant scientific interest. Our previous work has shown Pt oxide exhibits a higher CO2 electroreduction activity than Pt. In this study, the surface adsorption species on Pt and Pt oxide during electroreduction were investigated with SEIRAS to clarify the mechanisms of the superior electroreduction activity of Pt oxide. The main adsorption species during CO2 electroreduction were methanol and HCOO− on the Pt oxide, and methanol and linear-CO on the Pt. We confirmed that the CO2 electroreduction reaction proceeds via HCOO− on Pt oxide, and through CO on Pt. The CO2 electroreduction activity is significantly affected by the adsorption species because CO strongly adsorbs on the active site and inhibits subsequent reactions. The residual oxygen in the reduced Pt oxide electrode may cause the difference in adsorption species, controlling the reaction pathway. We conclude that the superior CO2 electroreduction activity of Pt oxide is due to the difference in the reaction pathway, possibly caused by residual oxygen and oxygen vacancies in the Pt oxide electrode.