Bismuth Nano-Flowers as a Highly Selective Catalyst for Electrochemical Reduction of CO₂to Formate

Electrochemical conversion of CO 2 into useful fuels provides tremendous potential for renewable energy storage. This study investigated a predominant nanostructure-dependent catalytic electroreduction of CO 2 into formate on Bi 2 O 3 electrode in 0.5 M KHCO 3 electrolyte. Compared with nano-particle Bi catalyst derived from Bi 2 O 3 nanorods (Bi 2 O 3 -R) electrode, the nano-flowered Bi in situ prepared via reduction of etched Bi 2 O 3 nanorods (Bi 2 O 3 -E) exhibited an enhanced catalytic activity for CO 2 electroreduction to formate. A relatively low overpotential of 530 mV was observed over Bi 2 O 3 -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 Bi 2 O 3 -R (FE = 67.9%). Experimental results revealed that the electrochemical active surface area and catalytic activity over reduced Bi 2 O 3 -E electrode were originated from the nano-flowered structure with abundant edge sites. The durability of catalytic activity over Bi 2 O 3 -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 CO 2 electroreduction.