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

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 (FEformate > 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.