Transition Metal Ion Doping on ZIF-8 for Enhanced the Electrochemical CO₂ Reduction Reaction

The electrochemical reduction of CO₂ to diverse value-added chemicals is a unique, environmentally friendly approach for curbing greenhouse gas emissions while addressing sluggish catalytic activity and low Faradaic efficiency (FE) of electrocatalysts. Here, zeolite-imidazolate-frameworks-8 (ZIF-8) containing various transition metal ions—Ni, Fe, and Cu—at varying concentrations upon doping were fabricated for the electrocatalytic CO₂ reduction reaction (CO₂RR) to CO without further processing. Atom coordination environments and theoretical electrocatalytic performance were scrutinized <i>via</i> X-ray absorption spectroscopy and density functional theory calculations. Upon optimized Cu doping on ZIF-8, Cu_0.5Zn_0.5/ZIF-8 achieved a high partial current density of 11.57 mA cm^–2 and maximum FE for CO of 88.5% at –1.0 V (vs. RHE) with a stable catalytic activity over 6 h. Furthermore, the electron-rich sp² C atom facilitated COOH* promotion after Cu doping of ZIF-8, leading to a local effect between the Zn–N₄ and Cu–N₄ moieties. Additionally, the advanced CO₂RR pathway was illustrated from various perspectives, including the pre-H-covered state under the CO₂RR. Our findings expand the pool of efficient MOF-based CO₂RR catalysts, deeming them viable alternatives to conventional catalysts.