Abstract: Electrocatalytic reduction of CO2 has been taken into consideration as a fascinating option to store energy from intermittent renewable sources in the form of chemical value-added products. Among the different value-added products, formic acid or formate is particularly attractive since it can be used as a fuel for low-temperature fuel-cells and as a renewable hydrogen carrier. Very recently, a rapidly increasing number of studies have revealed Bi as a promising electrocatalytic material for the CO2 electroreduction to formate, but the performance of Bi electrodes operating in a continuous mode and high current density (j) has been hardly investigated yet. Thus, this work aims at studying the CO2 electroreduction to formate working in a continuous mode in a filter-press-reactor at a j up to 300?mA·cm2 using Bi electrodes. Bismuth Gas Diffusion Electrodes (Bi-GDEs) were fabricated from carbon-supported Bismuth-nanoparticles. The influence of j and the electrolyte flow/area ratio in the performance of the Bi-GDEs towards formate were evaluated. Working at j of 300mA·cm2, a concentration of 5.2?g formate·L1 with a faradaic efficiency (FE) and rate of 70% and 11mmol·m2·s1, respectively were achieved. Lowering the j to 90mA·cm2, formate concentrations of up to 7.5g·L1 could be obtained with an excellent FE of 90%. Interestingly, the highest concentration of formate obtained was 18g·L1, but at expenses of an important decrease in FE. Although the results of this study are interesting and promising, further research is required to increase formate concentration for a future implementation at industrial scale.

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