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Title: Effects of Anion Identity and Concentration on Electrochemical Reduction of CO2

Journal Article · · ChemElectroChem
 [1];  [2];  [1];  [1];  [1]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
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The electrochemical reduction of CO2 is known to be influenced by the concentration and identity of the anionic species in the electrolyte; however, a full understanding of this phenomenon has not been developed. Here, we present the results of experimental and computational studies aimed at understanding the role of electrolyte anions on the reduction of CO2 over Cu surfaces. Experimental studies were performed to show the effects of bicarbonate buffer concentration and the composition of other buffering anions on the partial currents of the major products formed by reduction of CO2 over Cu. It was demonstrated that the composition and concentration of electrolyte anions has relatively little effect on the formation of CO, HCOO-, C2H4, and CH3CH2OH, but has a significant effect on the formation of H2 and CH4. Continuum modeling was used to assess the effects of buffering anions on the pH at the electrode surface. The influence of pH on the activity of Cu for producing H2 and CH4 was also considered. Changes in the pH near the electrode surface were insufficient to explain the differences in activity and selectivity observed with changes in anion buffering capacity observed for the formation of H2 and CH4. Therefore, it is proposed that these differences are the result of the ability of buffering anions to donate hydrogen directly to the electrode surface and in competition with water. The effectiveness of buffering anions to serve as hydrogen donors is found to increase with decreasing pKa of the buffering anion.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
AC02-05CH11231; SC0004993; DGE-0802270
OSTI ID:
1571098
Alternate ID(s):
OSTI ID: 1420191
Journal Information:
ChemElectroChem, Vol. 5, Issue 7; ISSN 2196-0216
Publisher:
ChemPubSoc EuropeCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 145 works
Citation information provided by
Web of Science

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Cited By (4)

Interplay of Homogeneous Reactions, Mass Transport, and Kinetics in Determining Selectivity of the Reduction of CO 2 on Gold Electrodes journal June 2019
In Situ Infrared Spectroscopy Reveals Persistent Alkalinity near Electrode Surfaces during CO 2 Electroreduction journal September 2019
Competition between CO 2 Reduction and Hydrogen Evolution on a Gold Electrode under Well-Defined Mass Transport Conditions journal February 2020
CO2 Electroreduction in Ionic Liquids journal March 2019

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