Hydrolysis of Electrolyte Cations Enhances the Electrochemical Reduction of CO2over Ag and Cu.
Electrolyte cation size is known to influence the electrochemical reduction of CO2over metals; however, a satisfactory explanation for this phenomenon has not been developed. We report here that these effects can be attributed to a previously unrecognized consequence of cation hydrolysis occurring in the vicinity of the cathode. With increasing cation size, the pKafor cation hydrolysis decreases and is sufficiently low for hydrated K+, Rb+, and Cs+to serve as buffering agents. Buffering lowers the pH near the cathode, leading to an increase in the local concentration of dissolved CO2. The consequences of these changes are an increase in cathode activity, a decrease in Faradaic efficiencies for H2and CH4, and an increase in Faradaic efficiencies for CO, C2H4, and C2H5OH, in full agreement with experimental observations for CO2reduction over Ag and Cu.
Joint Center for Artificial Photosynthesis, Material Science Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Department of Chemical Engineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
Meenesh R
MR
Singh
Carbon Resources Institute, Korea Research Institute of Chemical Technology , Daejeon 34114, Republic of Korea.|Joint Center for Artificial Photosynthesis, Material Science Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Youngkook
Y
Kwon
Joint Center for Artificial Photosynthesis, Material Science Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Yanwei
Y
Lum
Joint Center for Artificial Photosynthesis, Material Science Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Joel W
JW
Ager
Joint Center for Artificial Photosynthesis, Material Science Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Alexis T
AT
Bell