Abstract: Previous research in CO2 electroreduction primarily focused on cathodic electrocatalysts and electrode configurations using pure CO2. Few studies explored the impact of residence time and N2/O2 compounds, crucial for practical industrial implementation. In this study, the effect of residence time and the influence of N2 and O2 compounds on CO2 electroreduction to formate are investigated, employing Bi carbon-supported nanoparticles in the form of Gas Diffusion Electrodes within an electrochemical flow reactor with a single pass of the reactants. The results highlight the critical role of residence time and the impact of N2 and O2 compounds in the CO2 electroconversion process. On the one hand, the evaluation of residence time holds paramount significance for the potential establishment of a large-scale CO2 recycling plant, as it has the potential to significantly impact both the capital and operational costs of the integrated electrolyzer-separator system. Optimal results are obtained in the range of residence times between 1.8 and 2.9 seconds, corresponding to CO2 flow rates of 150 and 250mL·min-1, respectively. On the other hand, the study resulted in a promising Faradaic Efficiency for formate of 75.0%, with similar values achieved at CO2 concentrations in the range of 75- 100vol%. These results are particularly noteworthy as they demonstrate that achieving a CO2 capture efficiency of 100% is not necessary, thereby reducing the costs associated with this process and, consequently, the overall cost of integrating both capture and utilization processes in a CO2 recycling plant.

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