Electrochemical study on hydrogen evolution and CO2 reduction on Pt electrode in acid solutions with different pH

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