Electrochemical Study on Hydrogen Evolution and \rm C\rmO_\rm2 Reduction on Pt Electrode in Acid Solutions with Different pH

Hydrogen evolution reaction (HER) is the major cathodic reaction which competes \rm C\rmO_\rm2 reduction reaction (\rm C\rmO_\rm2 RR) on Pt electrode. Molecular level understanding on how these two reactions interact with each other and what the key factors are of \rm C\rmO_\rm2 RR kinetics and selectivity will be of great help in optimizing electrolysers for \rm C\rmO_\rm2 reduction. In this work, we report our results of hydrogen evolution and \rm C\rmO_\rm2 reduction on Pt(111) and Pt film electrodes in \rm C\rmO_\rm2 saturated acid solution by cyclic voltammetry and infrared spectroscopy. In solution with pH > 2, the major process is HER and the interfacial pH increases abruptly during HER; \rm C\rmO_\rmad is the only adsorbed intermediate detected in \rm C\rmO_\rm2 reduction by infrared spectroscopy; the rate for \rm C\rmO_\rmad formation increases with the coverage of UPD-H and reaches maximum at the onset potential for HER; the decrease of \rm C\rmO_\rmad formation under HER is attributed to the available limited sites and the limited residence time for the reduction intermediate (\rmH_\rmad), which is necessary for \rm C\rmO_\rm2 adsorption and reduction.