Structure Sensitivity of the Electrochemical Reduction of Carbon Monoxide on Copper Single Crystals

The product selectivity in the electrochemical reduction of carbon dioxide and carbon monoxide strongly depends on the atomic configuration of the copper electrode surface. On Cu(111), methane formation is favored, whereas on Cu(100), ethylene formation is favored, with selective ethylene formation at low overpotentials. To distinguish the reactivity of (100) terraces vs (100) steps, we have studied carbon monoxide reduction on Cu(322), with the [5(111) x (100)] orientation, and Cu(911), with the [5(100) x (111)] orientation. Only on Cu(911) is the selective ethylene formation at low overpotentials observed, indicating that this reaction pathway occurs only on (100) terraces. We also show that the reduction of ethylene oxide to ethylene is significantly faster on Cu(100) compared with Cu(111), giving further evidence to the importance of the associated intermediate for ethylene formation. On Cu(110), the potential dependence of methane and ethylene formation is similar to Cu(111), and we have observed a primary alcohol among the products.