Advances in the development of innovative Bi-Sn-Sb-based Gas Diffusion Electrodes for continuous CO2 electroreduction to formate

Abstract

The electrocatalytic reduction of CO₂ to formate or formic acid represents a promising approach to mitigating CO₂ emissions. Despite progress with Bi and Sn-based cathodes, there remains a demand for new electrocatalytic materials with enhanced activity for industrial-scale implementation. In a recent contribution, carbon-supported Bi-Sn-Sb nanoparticles with different atomic ratios were prepared and evaluated for the electrocatalytic reduction of CO₂ to formate, assessing their performance in terms of activity, selectivity, and stability under working conditions in an H-type cell. Under this electrochemical reactor configuration, the results clearly indicated that the incorporation of small amounts of Sb and Sn into Bi significantly enhanced stability without substantially affecting activity and selectivity, achieving promising results with Bi₈₀Sn₁₀Sb₁₀ electrocatalysts. Here, we report the use of Bi-Sn-Sb-based Gas Diffusion Electrodes (GDEs) in a flow electrochemical reactor for the electrocatalytic reduction of CO₂ to formate. The study also aims to rigorously compare the performance of Bi-Sn-Sb GDEs with that of analogous GDEs based solely on Bi or Sn. When compared to relevant references, the Bi-Sn-Sb catalyst demonstrates performance metrics that reflect comparable system efficiency to the Bi and Sn cathodes previously used by our research group, operating at current densities up to 200 mA·cm⁻² and achieving formate concentrations of approximately 15 g·L⁻¹. Furthermore, these materials exhibited technical feasibility, remaining stable throughout the 5-hour experiment with less than a 10 % decrease in concentration. This stability marks a vital first step toward the future implementation of this type of cathode in the electrochemical reduction of CO₂ to formate.