Bismuth-Catalyzed Electrochemical Carbon Dioxide Reduction to Formic Acid: Material Innovation and Reactor Design

ConspectusElectrochemical CO2 reduction reaction (eCO2RR) has gained increasing attention as a promising strategy to mitigate the negative impacts of CO2 emission while simultaneously producing valuable chemicals or fuels. By converting CO2 into energy-rich products using renewable electricity, eCO2RR provides a sustainable approach to reducing the carbon footprint and promoting a circular carbon economy. Among different reduction products, the formic acid (or formate) is particularly attractive due to its economic viability and diverse industrial applications, making it a key focus for both research and industrial adoption.Bismuth (Bi)-based electrocatalysts have emerged as promising candidates for eCO2RR to formic acid, by virtue of their nontoxicity, low cost, high abundance and exceptional selectivity for the two-electron pathway. These characteristics allow Bi-based catalysts to effectively suppress competing reactions and maximize formic acid production. In this Account, we discuss our contributions, along with those of others, to advancing the field of Bi-based materials for formic acid/formate production, focusing on both the fundamental understanding of their unique catalytic properties and innovative strategies employed to enhance their performances.One of our significant contributions lies in the development of advanced nanostructures that enhance the catalytic activity of Bi-based materials. By tailoring the size and morphology of Bi nanostructures, we have demonstrated improvements in active site density and reaction kinetics, leading to higher formic acid/formate selectivity and productivity. We have also explored the design of three-dimensional architectures, which provide enhanced mass transport and reduce diffusion limitations, thereby improving the overall efficiency of the catalytic process. Furthermore, works on defect engineering have revealed how modifying the electronic properties of Bi can optimize its binding affinity for key intermediates, significantly enhancing its catalytic performance.In addition to material innovations, recent research has contributed to the advancement of reactor designs that enable efficient and scalable eCO2RR systems. We have optimized flow cells to ensure continuous operation with high mass transport efficiency, making them suitable for industrial production. Furthermore, studies on membrane electrode assemblies (MEAs) have integrated Bi-based catalysts into compact and energy-efficient systems, furthering enhancing the practical applicability of eCO2RR. Solid-electrolyte systems have also been explored to simplify system configurations, improve stability and enable the production of pure formic acid. These efforts reflect the commitment of the community to bridging the gap between laboratory-scale research and industrial-scale implementation.Despite the significant progress achieved, challenges remain in fully realizing the potential of Bi-based eCO2RR technologies. Future efforts should focus on improving the long-term stability of catalysts, using advanced characterization techniques to gain deeper insights into reaction mechanisms, and further refining reactor configurations for large-scale applications. Addressing these challenges will be crucial to unlocking the full potential of Bi-based systems for sustainable chemical manufacturing.