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

Bi-based materials quickly rise as promising candidates for electrochemical CO2-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 CO2-toformate 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 mAcm(-2) in 0.1 M KHCO3. 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 *CO2 formation, resulting in high formate selectivity over a wider potential window. This work may pave the way for Bibased materials application in different renewable energyconversion devices.