Microwave-Assisted Synthesis of a Defect-Rich CuO Electrode for Selective Electrochemical CO2 Reduction to C2+ Products

Electrochemical reduction of CO2 to valuable C2+ chemicals using renewable energy is a crucial pathway for sustainable development, replacing traditional nonrenewable feedstocks. In this study, CuO-based materials were synthesized with and without microwave heating as electrocatalysts for CO2 reduction. The CuO synthesized under microwave irradiation (MW-CuO) showed a similar morphology to the conventionally heated samples but exhibited a higher density of defect sites with increased grain boundaries (GBs). MW-CuO electrodes with a Cu2+ and CO32- reactant ratio of 1.1 showed superior catalytic performance under identical reaction conditions. In particular, the catalytic activity of the MW-CuO electrode at -1.04 V vs RHE for the C2+ products is 49.3% higher than that of the CuO electrode. A faradaic efficiency (FE) of 71.9% is achieved for C2+ products, which is among the highest yields reported for OD-Cu catalysts. The spent MW-CuO electrode exhibited a significantly higher Cu+ to Cu-0 ratio compared to the CuO electrode. The synergy of Cu(I) species and defective surface features is speculated to be responsible for the improved CO2ER selectivity toward multicarbon products. However, the activity decreased for longer reactions, which was attributed to the loss of defect sites and Cu agglomerations. This study highlights the effectiveness of a simple synthesis approach for the production of defect-rich electrocatalysts that improve the efficiency and selectivity of CO2 reduction.