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Hydrolysis of Electrolyte Cations Enhances the Electrochemical Reduction of CO2over Ag and Cu

  • Author(s): Singh, MR
  • Kwon, Y
  • Lum, Y
  • Ager, JW
  • Bell, AT
  • et al.
Abstract

© 2016 American Chemical Society. 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.

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