Cu/Cu₂ O Electrodes and CO₂ Reduction to Formic Acid: Effects of Organic Additives on Surface Morphology and Activity

Copper/copper oxide (Cu/Cu₂ O) electrodes are known to display interesting electrocatalytic performances for the reduction of CO₂ , and thus, deserve further investigation for optimization. Here, we show that the addition of nitrogen-based organic additives greatly improves the activity of these electrodes (higher current densities, greater selectivity, and higher faradaic yields). The best effector is found to be tetramethyl cyclam. For example, electrolysis at -2.0 V versus Fc⁺ /Fc in CO₂ -saturated DMF/H₂ O (99:1, v/v) in the presence of this effector results in formic acid with almost 90 % faradaic yield. SEM and XPS analysis of the electrode surface reveals that the organic additive promotes the formation of active Cu⁰ nanoparticles from Cu₂ O during electrolysis. This simple approach provides a straightforward strategy toward the optimization of Cu/Cu₂ O electrodes.