Perovskite‐Derived Bismuth with I− and Cs+ Dual Modification for High‐Efficiency CO2‐to‐Formate Electrosynthesis and Al‐CO2 Batteries

Abstract Bi‐based materials are one of the most promising candidates for electrochemical CO 2 reduction reaction (CO 2 RR) to formate; however, the majority of them still suffer from low current density and stability that essentially constrain their potential applications at the industrial scale. Surface modification represents an effective approach to modulate the electrode microenvironment and the relative binding strength of key intermediates. Herein, it is demonstrated that the surface comodification with halides and alkali metal ions from the conversion of Bi‐based halide perovskite nanocrystals is a viable strategy to boost the CO 2 RR performance of Bi for formate electrosynthesis. Cs 3 Bi 2 I 9 nanocrystals are prepared by a hot‐injection method. The as‐prepared products feature well‐defined hexagonal shape and uniform size distribution. When used as the precatalyst, Cs 3 Bi 2 I 9 nanocrystals are converted to Cs + and I − comodified Bi. The resultant catalyst exhibits high formate Faradaic efficiency close to 100%, and remarkable partial current density up to 44 mA cm −2 in an H‐cell and up to 276 mA cm −2 in a flow cell. Moreover, Cs 3 Bi 2 I 9 is used as the cathode catalyst and paired with an Al anode in an Al‐CO 2 battery for simultaneous CO 2 valorization and power generation.