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. Bi5O7I and Bi7O9I3 nanosheets assemble irregularly, and BiOI nanosheets form a sphere-like structure. Compared with BiOI and Bi7O9I3, Bi5O7I 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 Bi3+ during electrolysis. The partial current densities of formate on BiOI were higher than those on Bi7O9I3 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.