Redox-neutral electrochemical conversion of CO2 to dimethyl carbonate

The electrochemical reduction of CO2 to value-added products is a promising approach for using CO2. However, the products are limited to reduced forms, such as CO, HCOOH and C2H4. Decreasing the anodic overpotential and designing membrane-separated systems are important determinants of the overall efficiency of the process. In this study we explored the use of redox-neutral reactions in electrochemical CO2 reduction to expand the product scope and achieve higher efficiency. We combined the CO2 reduction reaction with two redox cycles in an undivided cell so that the input electrons are carried through the electrolyte rather than settling in CO2. As a result, dimethyl carbonate—a useful fuel additive—has been synthesized directly from CO2 in methanol solvent with a Faradaic efficiency of 60% at room temperature. Our study shows that the formation of methoxide intermediates and the cyclic regeneration of the uniformly dispersed palladium catalyst by in situ-generated oxidants are important for dimethyl carbonate synthesis at room temperature. Furthermore, we successfully synthesized diethyl carbonate from CO2 and ethanol, demonstrating the generality and expandability of our system.