Chinese Journal of Catalysis ›› 2026, Vol. 80: 237-247.DOI: 10.1016/S1872-2067(25)64833-9

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

Juxia Xionga,b,1, Hao Maa,b,1, Yingjun Donga,b,1, Benjamin Liud, Xiangji Zhoua,b, Linbo Lia,b, Yuanmiao Suna,b,*(), Xiaolong Zhanga,b,*(), Hui-Ming Chenga,b,c,*()   

  1. aFaculty of Materials Science and Energy Engineering, Shenzhen University of Advanced Technology, Shenzhen 518107, Guangdong, China
    bShenzhen Key Laboratory of Energy Materials for Carbon Neutrality, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, Guangdong, China
    cShenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, Liaoning, China
    dDepartment of Environmental Science and Chemistry, Middlebury College, Middlebury, VT 05753, USA
  • Received:2025-03-19 Accepted:2025-08-14 Online:2026-01-18 Published:2026-01-05
  • Contact: Yuanmiao Sun, Xiaolong Zhang, Hui-Ming Cheng
  • About author:First author contact:1These authors contributed equally.
  • Supported by:
    National Natural Science Foundation of China(52201237);Shenzhen Science and Technology Innovation Bureau(KQTD2022110109364705);Shenzhen Science and Technology Innovation Bureau(ZDSYS2021070614400003);China Postdoctoral Science Foundation(E325281005);China Postdoctoral Science Foundation(E325281003);China Postdoctoral Science Foundation(2023M743670);Talent Introduction Project of Chinese Academy of Sciences(E344011);Joint Research Project of China Merchants Group and SIAT(E2Z1521);Cross Institute Joint Research Youth Team Project of SIAT(E25427);Postdoctoral Fellowship Program of CPSF(GZC20232867)

Abstract:

Bi-based catalysts are known to promote the electrochemical reduction of CO2 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 CO2 at a high current density.

Key words: CO2 reduction, Electrocatalysis, Bi-based catalyst, Polyaniline, Electron pump