Template‐Free Cu Electrodeposition to Prepare Cu–Micro‐Brush Electrodes for Electrochemical CO 2 Reduction

Abstract Copper foams deposited under various conditions are characterized in an airtight three‐electrode H‐cell system. Compared with the smooth copper electrode, the current density obtained on the porous copper electrodes is significantly improved. Using porous copper obtained from 0.2 M CuSO 4 and 1.5 M H 2 SO 4 electrolyte with 3 Acm −2 for 30s, the CO 2 reduction current density is 27 mAcm −2 at a potential of −0.97 V vs RHE in 0.5 M KHCO 3 electrolyte (with CO 2 supplied at the flow rate of 15 sccm), tripling that of the smooth copper electrode (8 mAcm −2 ). The average pore size of the porous copper can be reduced by adding Hexadecyltrimethylammonium bromide (CTAB) in a small amount. Besides, the preferred orientation of crystal faces changed, which may influence the selectivity of the carbon dioxide reduction product. In the flow‐cell test, at constant current 10 mAcm −2 , the CO production rate of porous copper with CTAB additive reached 11.91μmolh −1 cm −2 and maintained a value more than 8.95 μmolh −1 cm −2 during one‐hour electrolysis, which is much higher than smooth copper, 1.38 μmolh −1 cm −2 .