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 (CO2 RR) to CO without further processing. Atom coordination environments and theoretical electrocatalytic performance were scrutinized via X-ray absorption spectroscopy and density functional theory calculations. Upon optimized Cu doping on ZIF-8, Cu0.5 Zn0.5 /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 (versus 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, advanced CO2 RR pathway was illustrated from various perspectives, including the pre-H-covered state under the CO2 RR. Our findings expand the pool of efficient MOF-based CO2 RR catalysts, deeming them viable alternatives to conventional catalysts. This article is protected by copyright. All rights reserved.