Copper/Cobalt-Loaded Carbon Nanostructures as Catalysts for Electrochemical CO2 Reduction

The electrochemical reduction of CO2 to produce high-value multicarbon products represents a challenging yet highly desirable process, particularly due to the inefficient C–C coupling observed in current electrocatalysts. In this study, Cu2+ and Co2+ were introduced into ZIF-8 as precursors to synthesize a series of Co- and CuCo-doped carbon nanostructure materials with varying Co-to-Cu ratios. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) analyses confirmed the successful doping of metal Co in the form of Co–Nx, while Cu was partly doped as nanoparticles attached to the carbon substrate surface and partly as single atoms forming Cu–Nx. Transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses revealed uniform distribution of elemental Co and Cu on the carbon substrate, with Cu loaded as nanocluster on the surface. Linear sweep voltammetry tests indicated that Cu/CoCu-Nx-C composites exhibited enhanced reactivity toward CO2 reduction compared to other samples. At −0.19 V (vs RHE), the Faradaic efficiencies (FEs %) of C2H4, C2H6, CH4, CO, and H2 over Cu/CoCu-Nx-C were 29.7, 8.6, 20.2, 9.8, and 31.5%, respectively. The influence of Co and Cu doping modes on the selectivity of electrocatalytic reduction products was investigated. Results showed that Cu/CoCu-Nx-C exhibited a higher FE of C2 compared to Cu/Cu–Nx-C, with nearly 10 times higher C2 current density. Mechanistic insights from acid-etching experiments and XPS revealed a synergistic interaction between metallic Co and Cu, promoting the generation of multicarbon products. Co–Nx improved *CO coverage, facilitating subsequent C–C coupling on neighboring Cu–Nx. Additionally, CH4 production was attributed to the (111) crystalline facets in the Cu nanocluster and isolated Cu–Nx. Overall, this research provides an important understanding of the creation of straightforward and effective catalysts for the reduction of CO2. It holds considerable potential for the production of hydrocarbons using carbon dioxide.