The development of stable and selective electrocatalysts for converting CO2 to value-added chemicals or fuels has gained much interest in mitigating anthropogenic carbon emissions. Most electrocatalysts are tested under pure CO2; however, industrial outlet flue gas contains numerous impurities, such as NO and SO2, which poison the electrocatalysts and alter product selectivity. Developing electrocatalysts that are redundant to such impurities is essential for commercial implementation. In this regard, a set of bilayer porous electrocatalysts for selective conversion of CO2 to formic acid have been developed. The bilayer porous structure is obtained by depositing porous Cu foam structure on Cu foil or mesh substrates using the hydrogen bubble template method. Subsequently, Sn/Bi/In catalyst particles were electrodeposited on Cu foam to enhance selectivity towards formic acid. It was observed that foam deposited electrocatalysts exhibit excellent CO2 reduction compared to the catalysts coated on bare Cu (foil or mesh). Among all synthesized catalysts, Sn/Cu-f mesh and Bi/Cu-f mesh showed over 80% formate Faradaic efficiency, indicating that the selectivity of both the catalysts towards formate is high. These high performing catalysts were tested in the presence of poisonous NO and SO2 along with CO2 to assess their effect on selectivity and stability towards formate. Notably, Bi/Cu-f mesh electrocatalyst showed remarkable stability for 50 h with 80±5% formate Faradaic efficiency, while Sn/Cu-f mesh showed 18 h stability with 80±5% efficiency. Further, scanning electrochemical microscopy (SECM) studies were employed to obtain a deeper understanding of the activity of electrodes during the reaction, which helped interpret the results from the bulk studies.
The efficacy and stability of the developed bilayer porous catalysts for selectively converting flue gas CO2 to formic acid were demonstrated through bulk and in-situ electrochemical studies.