Altering the selectivity of galvanostatic {CO2} reduction on Cu cathodes by periodic cyclic voltammetry and potentiostatic steps

By Lim, C. F. C.; Harrington, D. A.; Marshall, A. T.
Published in Electrochimica Acta NULL 2016

Abstract

Abstract Analysis of the product selectivity and potential of Cu cathodes during galvanostatic {CO2} reduction is reported. Initially, it is found that clean Cu cathodes are more selective for hydrogen evolution, but as the Cu is slowly poisoned by {CO2} reduction products (most likely carbon) the cathode potential becomes more negative, which in turn drives the formation of CH4, {C2H4} and CO. As the accumulation of surface poisons continues, the selectivity towards {CH4} and {C2H4} begins to decrease due to the loss in neighbouring reaction sites that support the hydrogenation of {COads} by Hads. In an attempt to avoid these changes in product selectivity, periodic cyclic voltammetry and potentiostatic steps were used throughout extended periods of galvanostatic {CO2} reduction. Contrary to previous literature, it is demonstrated that temporarily interrupting galvanostatic {CO2} reduction with short periods at potentials between ?0.5 and ?0.1 V vs Ag|AgCl suppresses the formation of CH4, {CO} and C2H4. It is proposed that this is due to the partial removal or oxidation of adsorbed {CO2} reduction intermediates and that this

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