The Central Role of Bicarbonate in the Electrochemical Reduction of Carbon Dioxide on Gold

摘要

Much effort has been devoted in the development of efficient catalysts for electrochemical reduction of CO_2. Molecular level understanding of electrode-mediated process, particularly the role of bicarbonate in increasing CO_2 reduction rates, is still lacking due to the difficulty of directly probing the electrochemical interface. We developed a protocol to observe normally invisible reaction intermediates with a surface enhanced spectroscopy by applying square-wave potential profiles. Further, we demonstrate that bicarbonate, through equilibrium exchange with dissolved CO_2, rather than the supplied CO_2, is the primary source of carbon in the CO formed at the Au electrode by a combination of in situ spectroscopic, isotopic labeling, and mass spectroscopic investigations. We propose that bicarbonate enhances the rate of CO production on Au by increasing the effective concentration of dissolved CO_2 near the electrode surface through rapid equilibrium between bicarbonate and dissolved CO_2.