Electrochemical reduction of carbon dioxide at various series of copper single crystal electrodes

Electrochemical reduction of carbon dioxide was studied with various series of copper single crystal electrodes in 0.1 M KHCO3 aqueous solution at constant current density 5 mA cm−2; the electrodes employed are Cu(S)-[n(100)×(111)], Cu(S)-[n(100)×(110)], Cu(S)-[n(111)×(100)], Cu(S)-[n(111)×(111)] and Cu(S)-[n(110)×(100)]. The electrodes based on (1 0 0) terrace surface give ethylene as the major product. The ethylene formation is further promoted by the introduction of (1 1 1) or (1 1 0) steps to the (1 0 0) basal plane. The highest C2H4 to CH4 formation ratio amounts to 10 in terms of the current efficiency for the (7 1 1) (=4(1 0 0) − (1 1 1)) surface as compared with the value 0.2 for the (1 1 1) electrode. The n(111)−(111) surfaces favor the formations of acetic acid, acetaldehyde and ethyl alcohol with the increase of the (1 1 1) step atom density. CH4 formation at the n(111)−(111) electrodes decreases with the increase of the (1 1 1) step atom density. The n(111)−(100) surfaces give higher gaseous products; the major product is CH4 with lower fraction of C2+ compounds.