Influence of the Chemical Compositions of Bismuth Oxyiodides on the Electroreduction of Carbon Dioxide to Formate

Abstract Bismuth oxyiodides with varying chemical compositions were fabricated to effectively electrochemical reduce CO 2 to formate. Bi 5 O 7 I and Bi 7 O 9 I 3 nanosheets assemble irregularly, and BiOI nanosheets form a sphere‐like structure. Compared with BiOI and Bi 7 O 9 I 3 , Bi 5 O 7 I exhibits an excellent Faradaic efficiency of 89 % for formate production with the partial current density of 13.2 mA/cm 2 at −0.89 V vs. RHE owing to the elevated amounts of Bi metal sites reduced from Bi 3+ during electrolysis. The partial current densities of formate on BiOI were higher than those on Bi 7 O 9 I 3 which is attributed to the higher iodine content. The synergistic effect of bismuth and iodine of bismuth oxyiodides is responsible for their electrocatalytic properties during CO 2 reduction in aqueous solutions.