Improving the electrocatalytic CO2 to formate conversion on bismuth using polyaniline as an electron pump

Bi-based catalysts are known to promote the electrochemical reduction of CO 2 to formic acid (HCOOH) or formate (HCOO − ). However, their implementation presents challenges: the first H + /e − pair transfer to form the key *OCHO intermediate on a Bi surface is a slow, kinetically sluggish endergonic process, resulting in a large overpotential and narrow potential window for high HCOOH/HCOO − selectivity. Altering the localized p -orbital electron states of Bi to change intermediate binding behaviors is difficult. We addressed this problem by using an in-situ polymerization method to obtain a polyaniline-Bi hybrid (PANI-Bi) with Bi surrounded by PANI chains. Combined experimental and computational studies indicate that the polyaniline acted as an “electron pump” that facilitated charge transfer from the PANI backbone to the Bi surface and changed the p -orbital electrons of the Bi active sites. This lowered the energy barrier for the adsorption of intermediates and facilitated *OCHO formation. Consequently, a significant increase in formate production was observed, achieving a single-pass carbon efficiency exceeding 48.7% at 800 mA cm −2 . This organic functionalization strategy, aimed at modifying the electronic structure of heterogeneous catalysts, offers a promising approach for achieving highly selective electroreduction of CO 2 at a high current density.