Electroreduction of Carbon Dioxide on Copper-Based Electrodes: Activity of Copper Single Crystals and Copper–Gold Alloys

Abstract

The activity of copper single-crystal and copper–gold alloyed (Au1Cu99, Au10Cu90, Au20Cu80, Au50Cu50) electrodes for CO2 electroreduction has been investigated in aqueous phosphate buffer solutions by cyclic voltammetry and potentiostatic long-term electrolysis. In addition to H2, four species were identified in the gaseous phase by chromatography after electrolyses: CO, CH4, C2H4 and traces of C2H6. At copper electrodes, the major carbon-containing products are CO and CH4. Analysis of the data indicates that the fraction of methane increases in the order Cu (poly) < Cu (100) < Cu (111), whereas a concomitant decrease of the carbon monoxide fraction is observed. The selectivity of low-index faces towards methane formation is consistent with a mechanism involving CO(ads) and H(ads). Analytical information obtained after potentiostatic electrolyses at copper–gold alloys shows that the CO production increases markedly with the Au content, while the fraction of CH4 diminishes. Amongst all the examined electrodes, the Au50Cu50 alloy appears to be the most efficient substrate for the conversion of CO2 into carbon-containing gaseous products.