Optimisation of the electrochemical conversion of CO2 into formate in a flow cell configuration using a bismuth-based electrocatalyst

Abstract

Highly selective and active electrocatalysts are essential for industrial application of the electrochemical conversion of CO₂ into valuable products. The electrochemical cell configuration and the optimisation of its parameters are also of paramount importance to promote the conversion of CO₂ and enhance the selectivity and stability of the electrocatalyst. Furthermore, the cell needs to be designed to enable the continuous conversion of CO₂ in a flow cell configuration with optimal use of energy resources, to obtain a sustainable CO₂-to-formate conversion process. In this work, we present an in-depth, systematic investigation of the crucial parameters for the optimum operation of a flow cell for the conversion of CO₂ with a highly scalable Bi-based electrocatalyst at industrially-relevant current densities (j = 100 mA cm⁻²), achieving high Faradaic efficiency (FE_formate > 70%) for a prolonged application time (t = 65 h). By studying and tuning the electrolyte and CO₂ feed flow, the membrane configuration, the pH of the electrolyte and the effect of possible contaminants in the CO₂ source, we were able to gain important insights into the large-scale application of the Bi-based electrocatalyst for the electrochemical reduction of CO₂ into formate.