In Situ Structure Refactoring of Bismuth Nanoflowers for Highly Selective Electrochemical Reduction of CO2 to Formate

Abstract The electrocatalytic CO2 reduction reaction (CO2RR) has been considered a promising route toward carbon neutrality and renewable energy conversion. At present, most bismuth (Bi) based electrocatalysts are adopted to reduce CO2 to formate (HCOOH). However, the mechanism of different Bi nanostructures on the electrocatalytic performance requires more detailed exposition. Herein, a combined chemical replacement and electrochemical reduction process is reported to realize in situ morphology reconstruction from Bi@Bi2O3 nanodendrites (Bi@Bi2O3‐NDs) to Bi nanoflowers (Bi‐NFs). The Bi@Bi2O3‐NDs are proven to undergo a two‐step transformation process to form Bi‐NFs, aided by Bi2O2CO3 as the intermediate in KHCO3 solution. Extensive surface reconstruction of Bi@Bi2O3‐NDs renders the realization of tailored Bi‐NFs electrocatalyst that maximize the number of exposed active sites and active component (Bi0), which is conducive to the adsorption and activation of CO2 and accelerated electron transfer process. The as‐prepared Bi‐NFs exhibit a Faradaic efficiency (FEformate) of 92.3% at −0.9 V versus RHE and a high partial current density of 28.5 mA cm−2 at −1.05 V versus RHE for the electroreduction of CO2 to HCOOH. Moreover, the reaction mechanism is comprehensively investigated by in situ Raman analysis, which confirms that *OCHO is a key intermediate for the formation of HCOOH.