Controlled Selectivity of CO ₂ Reduction on Copper by Pulsing the Electrochemical Potential

Abstract We demonstrate a simple strategy to enhance the CO 2 reduction reaction (CO 2 RR) selectivity by applying a pulsed electrochemical potential to a polycrystalline copper electrode. By controlling the pulse duration, we show that the hydrogen evolution reaction (HER) is highly suppressed to a fraction of the original value (<5 % faradaic efficiency) and selectivity for the CO 2 RR dramatically improves (>75 % CH 4 and >50 % CO faradaic efficiency). We attribute the improved CO 2 RR selectivity to a dynamically rearranging surface coverage of hydrogen and intermediate species during the pulsing. Our finding provides new insights into the interplay of transport and reaction processes as well as timescales of competing pathways to enable new opportunities to tune CO 2 RR selectivity by adjusting the pulse profile. Additionally, the pulsed potential method we describe can be easily applied to other catalysts materials to improve their CO 2 RR selectivity.