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

Abstract The electrocatalytic CO 2 reduction reaction (CO 2 RR) has been considered a promising route toward carbon neutrality and renewable energy conversion. At present, most bismuth (Bi) based electrocatalysts are adopted to reduce CO 2 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@Bi 2 O 3 nanodendrites (Bi@Bi 2 O 3 ‐NDs) to Bi nanoflowers (Bi‐NFs). The Bi@Bi 2 O 3 ‐NDs are proven to undergo a two‐step transformation process to form Bi‐NFs, aided by Bi 2 O 2 CO 3 as the intermediate in KHCO 3 solution. Extensive surface reconstruction of Bi@Bi 2 O 3 ‐NDs renders the realization of tailored Bi‐NFs electrocatalyst that maximize the number of exposed active sites and active component (Bi 0 ), which is conducive to the adsorption and activation of CO 2 and accelerated electron transfer process. The as‐prepared Bi‐NFs exhibit a Faradaic efficiency (FE formate ) 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 CO 2 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.