BiO2.xNanosheets with Surface Electron Localizations for Efficient Electrocatalytic CO2 Reduction to Formate

To enhance the activity and selectivity of electrocatalytic CO2 reduction to formate is of great importance from both environmental and economical viewpoints. Herein, the BiO2-x nanosheets with surface electron localizations were constructed and utilized for the efficient CO2-to-formate conversion. The formate Faraday efficiency reaches 99.1% with current density of 12 mA cm-2 at -1.1 V versus the reversible hydrogen electrode (RHE) in an H-type cell while those in the flow cell are 91.3% and 319 mA cm-2 at -1.0 V versus RHE, respectively. Theoretical calculations indicate that the electron localization presenting in the BiO2-x nanosheet favors OCHO* intermediate stabilization and suppresses H* intermediate adsorption, thus improving the CO2-to-formate efficiency. The BiO2-x electrocatalyst is nondopant, easily prepared, low-cost, highly active and selective for CO2RR to formate, which has demonstrated potential for application in the Zn-CO2 battery. The maximum power density can reach 2.33 mW cm-2, and the charge/discharge cycling stability is >100 h (300 cycles) at 4.5 mA cm-2.