Efficient and cost-effective electrocatalytic CO2 to CO reduction over Sn-modified Cu nanowires by pairing with selective HCHO to HCOOH oxidation

Abstract

Electrocatalytic CO2 reduction reaction (CO2RR) over Cu-based electrocatalysts still suffered from low efficiency but high energy consumption. In this study, atomic-dispersed Sn-modified Cu nanowires (Cu@Sn NWs) were synthesized for selective electrocatalytic CO2RR to CO with an optimized FECO of 96.4 %. Moreover, formaldehyde oxidation half-reaction (FOR) at MnO2/CP anode, replacing water oxidation (WOR), was introduced to build a novel CO2RR/FOR system with CO2RR over Cu@Sn NWs, to further improve CO2RR efficiency and to reduce the energy consumption. Generally, compared with CO2RR/WOR system, CO2RR/FOR system shows a much higher CO2RR performance. Meanwhile, HCHO can be converted to HCOOH at MnO2/CP anode with tunable selectivity (50 ∼ 65 %), depending on the applied cell voltage. Specifically, at a cell voltage of 3.5 V, about 97.9 % of HCHO can be removed with HCHO→HCOOH selectivity of about 50 %. Moreover, the working cell voltage and energy consumption can be significantly reduced over CO2RR/FOR system, versus CO2RR/WOR system. For example, at the current density of − 4 mA/cm2 (FECO = ∼95 %), the cell voltage is lower by about 270 mV, and the energy consumption is lower by about 8.97 %. Compared with the sum of the energy consumption of a single CO2RR and FOR, the energy consumption of the CO2RR/FOR system can be reduced by about 47.3 %. When solar cells were used as the power supply, the CO generation rate in the CO2RR/FOR system is about 1.43 times that in the CO2RR/WOR system, accompanied by the anodic conversion of HCHO to HCOOH with the selectivity of 58.2 %.