▎ 摘　　要

Electrocatalytic CO2 reduction (CO2ER) into formate is a desirable route to achieve efficient transformation of CO2 to value-added chemicals, however, it still suffers from limited catalytic activity and poor selectivity. Herein, we develop a hybrid electrocatalyst composed of bismuth and bismuth oxide nanoparticles (NPs) supported on nitrogen-doped reduced graphene oxide (Bi/Bi2O3/NrGO) nanosheets prepared by a combined hydrothermal with calcination treatment. Thanks to the combination of undercoordinated sites and strong synergistic effect between Bi and Bi2O3, Bi/Bi2O3/NrGO-700 hybrid displays a promoted CO2ER catalytic performance and selectivity for formate production, as featured by a small onset potential of -0.5 V, a high current density of -18 mA/cm(2), the maximum Faradaic efficiency of 85% at -0.9 V, and a low Tafel slope of 166 mV/dec. Experimental results reveal that the higher CO2ER performance of Bi/Bi2O3/NrGO-700 than that of Bi NPs supported on NrGO (Bi/NrGO) can be due to the partial reduction of Bi2O3 NPs into Bi, which significantly increases undercoordinated active sites on Bi NPs surface, thus boosting its CO2ER performance. Furthermore, a two-electrode device with Ir/C anode and Bi/Bi2O3/NrGO-700 cathode could be integrated with two alkaline batteries or a planar solar cell to achieve highly active water splitting and CO2ER. (C) 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.