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

• Bi-ZIF-8 was synthesized by one step facile method. • The ZIF-8 framework hosts the high dispersion of Bi nanodots. • Bi-ZIF-8 electrocatalyst show high performance for the CO₂ reduction to formate. • Bi-ZIF-8 allows a high Faradic efficiency at high current density. Zeolitic imidazolate framework-based electrocatalysts for CO 2 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 CO 2 . Still, they were not investigated sufficiently. In this study, we developed a Bismuth nanodots embedded Zeolitic Imidazolate Framework-8 (Bi-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 Bi-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/cm². 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.