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–N_x, while Cu was partly doped as nanoparticles attached to the carbon substrate surface and partly as single atoms forming Cu–N_x. 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-N_x-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-N_x-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-N_x-C exhibited a higher FE of C₂ compared to Cu/Cu–N_x-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–N_x improved *CO coverage, facilitating subsequent C–C coupling on neighboring Cu–N_x. Additionally, CH₄ production was attributed to the (111) crystalline facets in the Cu nanocluster and isolated Cu–N_x. 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.