CO₂ electroreduction on nano-Cu-ZIF grown inside activated carbon: experimental and computational aspects

Electrochemical reduction of CO₂ (CO₂RR) offers a sustainable approach to simultaneously lower atmospheric CO₂ levels and convert it into useful chemicals. While noble metals are currently the most effective catalysts for this process, their expense limits large-scale use, driving the search for more affordable alternatives. Transition-metal sites incorporated within metal-organic frameworks (MOFs) show great catalytic promise; however, the inherently poor conductivity of MOFs remains a significant obstacle. The porous structure of activated carbon provides a high surface area for efficient electron transport and CO₂ adsorption, while the encapsulated MOF imparts catalytic sites with tuneable electronic properties and molecular selectivity. The synergistic interaction between the MOF and AC enhances the availability of active sites, conductivity, improves charge transfer kinetics, and suppresses competing hydrogen evolution. In this work, Cu-Zeolitic Imidazole Framework (Cu-ZIF) nanoparticles were grown directly within a hierarchically porous activated carbon matrix, rather than physically blended with conductive additives. This encapsulation strategy resulted in composites with enhanced conductivity, maintained Cu-ZIF crystallinity, and strong electronic coupling between the components. When applied to electrochemical CO₂RR, the Cu-ZIF@AC composite achieved low overpotential of -0.56 V (vs. RHE) at -10 mA cm^-2 current density, surpassing the performance of usually reported MOF-based systems. Moreover, the catalyst selectively produced acetic acid (71.5% faradaic efficiency) at -0.3 V (vs. RHE) onset potential demonstrating excellent potential for efficient and scalable CO₂ electroreduction.