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

Bismuth oxyiodides with varying chemical compositions were fabricated to effectively electrochemical reduce CO2 to formate. Bi5 O7 I and Bi7 O9 I3 nanosheets assemble irregularly, and BiOI nanosheets form a sphere-like structure. Compared with BiOI and Bi7 O9 I3 , Bi5 O7 I exhibits an excellent Faradaic efficiency of 89 % for formate production with the partial current density of 13.2 mA/cm2 at -0.89 V vs. RHE owing to the elevated amounts of Bi metal sites reduced from Bi3+ during electrolysis. The partial current densities of formate on BiOI were higher than those on Bi7 O9 I3 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 CO2 reduction in aqueous solutions.