Improving Stability and Selectivity in Electrochemical Reduction of Carbon Dioxide in an Aqueous Solution

With the rising level of CO2 in the atmosphere, methods capable of converting CO2 into useful fuels are urgently needed. The electrochemical CO2 reduction has gained significant interest recently due to its ability to use renewable energies. However, the poor stability of catalysts in electrochemical CO2 reduction limit its application in industry. Here we have developed a light-involving method to remove the surface carbonaceous species which are believed to poison the catalysts. By taking advantage of plasmonic properties of the copper catalyst, the stability of the catalysts has apparently improved.

Another problem in electrochemical CO2 reduction is the poor selectivity. One of the main reasons is the existence of the side reaction, hydrogen evolution reaction. Here we have developed a catalyst by dispersing atomic nickel on nitrogen-doped winged carbon nanotubes with the ability to suppress hydrogen evolution during CO2 reduction. The Faradaic Efficiency of CO reached 90% at -1.6 V vs. AgCl/Ag reference electrode while the efficiency of HER had been suppressed to less than 10% in the optimal reaction condition. By comparing with Ni NPs, the suppression of HER can be directly observed in LSV curve. It is suggested that this suppression may result from the lack of adjacent active sites for the Tafel mechanism in HER.