Enhanced Electroconversion CO2‐to‐Formate by Oxygen‐Vacancy‐Rich Ultrasmall Bi‐Based Catalyst Over a Wide Potential Window

Abstract Bi‐based materials quickly rise as promising candidates for electrochemical CO 2 ‐to‐formate conversion. However, most of them only display a narrow potential range for the desired formate selectivity. Herein, we designed an oxygen‐vacancy‐rich ultrasmall bismuth subcarbonate supported on reduced graphene oxide composite (Vo‐BOC/G) for electrochemical CO 2 ‐to‐formate conversion. The Vo‐BOC/G exhibits an outstanding formate selectivity up to 100 % at −1.2 V vs. RHE and an impressive partial current density of 38 mA cm −2 in 0.1 M KHCO 3 . More importantly, the considerable formate selectivity (>80 %) was obtained over an impressively wide potential range of 600 mV, superior over most of reported Bi‐based electrocatalysts under the same conditions. Theoretical results show the abundant Vo defects significantly lower energy barrier for *CO 2 formation, resulting in high formate selectivity over a wider potential window. This work may pave the way for Bi‐based materials application in different renewable energy‐conversion devices.