Hydrolysis of Electrolyte Cations Enhances the Electrochemical Reduction of CO2 over Ag and Cu
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Date
2016-10-05Author
Singh, Meenesh R.
Kwon, Youngkook
Lum, Yanwei
Ager III, Joel W.
Bell, Alexis T.
Publisher
American Chemical SocietyMetadata
Show full item recordAbstract
Electrolyte cation size is known to influence the electrochemical reduction of CO2 over
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 vicinity of the cathode. With increasing cation size, the pKa for
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 H2 and CH4 and an increase in Faradaic
efficiencies for CO, C2H4, and C2H5OH in full agreement with experimental observations for CO2 reduction over Ag and Cu.
Subject
Electrochemical CO2 ReductionCation hydrolysis
Polarization loss