Electrochemical conversion of CO2 into useful fuels provides tremendous potential for renewable energy storage. This study investigated a predominant nanostructure-dependent catalytic electroreduction of CO2 into formate on Bi2O3 electrode in 0.5 M KHCO3 electrolyte. Compared with nano-particle Bi catalyst derived from Bi2O3 nanorods (Bi2O3-R) electrode, the nano-flowered Bi in situ prepared via reduction of etched Bi2O3 nanorods (Bi2O3-E) exhibited an enhanced catalytic activity for CO2 electroreduction to formate. A relatively low overpotential of 530 mV was observed over Bi2O3-E electrode for formate generation, and the maximum faradaic efficiency (FE) was achieved 99.2% at -1.5 V vs SCE with operating at a current density of 7.5 mA cm(-2), which was superior to that of Bi2O3-R (FE = 67.9%). Experimental results revealed that the electrochemical active surface area and catalytic activity over reduced Bi2O3-E electrode were originated from the nano-flowered structure with abundant edge sites. The durability of catalytic activity over Bi2O3-E lasted at least for 20 h of continuous reaction with negligible decline of FE and current density. This insight may benefit for the further design of surface morphology and structure devoting to improving the catalytic efficiency for CO2 electroreduction. (C) 2018 The Electrochemical Society.