Highly efficient CO₂ electroreduction to formate using Bismuth nanodots within ZIF-8 scaffold

Zeolitic imidazolate frameworks (ZIFs) based electrocatalysts for CO₂ reduction offer unique possibilities for developing advanced materials for this reaction due to their ordered nanoporosity and pore environments, tunable characteristics and high affinity for CO₂. Still, they were not investigated sufficiently. In this study, we developed a Bismuth nanodots embedded Zeolitic Imidazolate Framework-8 (BND-ZIF-8) electrocatalyst via a one-pot synthesis method for the electrochemical CO₂ reduction reaction (eCO₂RR). Comprehensive spectroscopic and electrochemical characterization confirmed the successful integration of Bismuth into the ZIF-8 matrix. The electrocatalytic performance of the BND-ZIF-8 was assessed in multiple reactor typologies such as H-cell, flow cell, and membrane electrode assembly (MEA) setups. Remarkable differences in the performances in the three cell configurations are evidenced. Notably, the MEA configuration exhibited a marked enhancement in formate selectivity, achieving a Faradic efficiency (FE) of up to 91 % at a current density of −150 mA cm^‒². This work underscores the potential of Bi-ZIF-8 in advancing eCO₂RR while remarking on the crucial importance of the appropriate type of electrocatalytic experiments in assessing the material performance.