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Bismuth-based materials are prevalent catalysts for CO2 electroreduction to formate, enduring high hydrogen evolution reactions and inadequate activity and stability. Herein, we reveal that in-situ electrochemical transformation of Cu2BiSx solid solution into Bi/CuxSy heterointerfaces, which can stabilize the intermediates and achieve highly selective and consistent CO2 electroreduction. It shows over 85% Faraday efficiency (FE) of formate with a potential window of −0.8 to −1.2 VRHE (RHE: reversible hydrogen electrode) and a stability above 90% over 27 h in H-type cell at −0.9 VRHE. It maintains more than 85% of FEformate at the current density of −25 to −200 mA·cm−2, and has stability of about 80% of FEformate at least 10 h at −150 mA·cm−2 in flow cell. In-situ Fourier transform infrared (FT-IR) spectroscopy measurement confirms that the preferred route of catalytic reaction is to generate *CO2− and *OCHO intermediates. The density functional theory (DFT) calculations illustrate that heterointerfaces facilitate the prior process of CO2 to HCOOH through *OCHO by additional Bi hybrid orbitals. This study is expected to open up a new idea for the design of CO2 electroreduction catalyst.
This work was supported by the National Natural Science Foundation of China (Nos. 21871005 and 22171005) and the University Synergy Innovation Program of Anhui Province (Nos. GXXT-2020-005, GXXT-2021-012, and GXXT-2021-013).