Multi-products (C1 and C2) Formation from Electrochemical Reduction of Carbon Dioxide Catalyzed by Oxide-Derived Coppers Prepared Using Varied Synthesis Conditions

In order to explore the effects of morphology, specific surface area and relative content of Cu/Cu-oxide in CuO-derived Cu electrocatalysts on the current density and product formation during electrochemical carbon dioxide reduction reaction (eCO(2)RR), CuO electrocatalysts were synthesized via solution combustion and hydrothermal routes, possessing different morphologies. The as-synthesized CuOs were first reduced to Cu at - 0.8 V (vs. RHE), till the currents got stabilized; thus, forming CuO-derived Cu . Subsequently, eCO(2)RR was carried out via bulk electrolysis at different potentials between - 0.6 and - 1.6 V (using 0.1 M KHCO3 solution), leading to the formation of seven liquid/gaseous products, viz., CO, methane, ethylene, formate, acetate, and ethanol (in addition to H-2). It was interesting to note that the type of products and associated faradic efficiencies (FEs) were governed by the Cu-content of the CuO-derived Cu electrocatalysts (i.e., Cu:CuO ratio), as obtained post the pre-reduction step and looked into here as one of the starting conditions of the electrocatalysts. Higher initial Cu-content of the pre-reduced CuOs resulted in higher FEs at lower negative potentials. Furthermore, high Cu-content (even for simple equiaxed morphology), as opposed to any special morphology (say, rod/whisker-type), has been found to be particularly important for the formations of methane and formate; yielding a maximum FE of similar to 18.6 +/- 1.2% at - 1.0 V for the latter. Accordingly, the present work reveals the relative roles of specific surface area and Cu/CuO-content of CuO-derived Cu electrocatalysts on the current densities, product formation and associated FEs on eCO(2)RR.

Automated summary

This study investigates the effects of morphology, specific surface area, and relative content of Cu/Cu-oxide in CuO-derived Cu electrocatalysts on the current density and product formation during electrochemical carbon dioxide reduction reaction (eCO(2)RR). The results show that the Cu-content of the CuO-derived Cu electrocatalysts determines the type of products and their corresponding faradic efficiencies, with higher initial Cu-content resulting in higher faradic efficiencies at lower negative potentials. Furthermore, it is found that high Cu-content, regardless of morphology, is particularly important for the formation of methane and formate. Therefore, this study reveals the relative roles of specific surface area and Cu/CuO-content of CuO-derived Cu electrocatalysts on the current densities, product formation, and associated faradic efficiencies in eCO(2)RR.