Perovskite-Derived Bismuth with I - and Cs + Dual Modification for High-Efficiency CO 2 -to-Formate Electrosynthesis and Al-CO 2 Batteries.

Bi-based materials are one of the most promising candidates for electrochemical CO 2 reduction 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, thereby significantly impacting the electrocatalytic performances. Herein, we demonstrate that the surface co-modification with halides and alkali metal ions from the conversion of bismuth halide perovskite nanocrystals is a viable strategy to boost the CO 2 RR performance of bismuth for formate electrosynthesis. As a proof of concept, 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 - co-modified Bi. The resultant catalyst exhibits high formate Faradaic efficiency close to 100%, and remarkable partial current density up to 44 mA cm -2 at -0.92 V (versus reversible hydrogen electrode, RHE) in an H-cell and up to 276 mA cm -2 at -0.75 V (versus RHE) in a flow cell as well as great stability. Those performance metrics exceed most of its competitors under similar conditions. 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. A peak power density of 7 mW cm -2 is measured at room temperature. This article is protected by copyright. All rights reserved.