Role of surface oxide layer during CO 2 reduction at copper electrodes

Document Type

Conference Proceeding

Publication Date

10-23-2012

Abstract

We have compared the rates of CO formation on Cu and Cu oxide surfaces during the electrochemical reduction of CO 2 in aqueous media. On metallic Cu surfaces, H 2 formation is the main reaction at potentials less cathodic than -1.16 V(NHE). At this potential the formation of CO becomes significant, while CH 4 appears at potentials more cathodic than -1.36 V(NHE). On electrodeposited Cu oxide surfaces there is a complex transient response. During reduction at constant potential (-1.1 V(NHE)), there is a large, transient cathodic current that corresponds to reduction of the oxide layer. After this initial oxide reduction, the current density stabilizes and the formation rates of H 2 and CO show a more slowly varying transient behavior. The H 2 formation rate is roughly 3x higher than on freshly cleaned Cu foil, but is largely independent of the thickness of the initial oxide layer. In contrast, the CO formation rate is at least one order of magnitude higher on the (reduced) Cu oxide samples than on Cu foil at the same potential. These results are interpreted as evidence that CO formation is enhanced at low-coordination number Cu sites present on freshly nucleated Cu clusters following oxide reduction. © 2012 Materials Research Society.

Publication Source (Journal or Book title)

Materials Research Society Symposium Proceedings

First Page

59

Last Page

64

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