Investigation of the Mechanisms of CO 2 /O 2 Adsorption Selectivity on Carbon Materials Enhanced by Oxygen Functional Groups.

Power plant flue gas and industrial waste gas are produced in large quantities. Using these as feedstocks for CO 2 electroreduction has important practical significance for the treatment of excessive CO 2 emissions. However, O 2 in such sources strongly inhibits the electrochemical conversion of CO 2 . The inhibitory effect of O 2 can be mitigated by constructing CO 2 -enriched regions on the surface of the cathode. In this study, the reaction zone was controlled by the selective adsorption of CO 2 on oxygen-functionalized carbon materials. The results of quantum chemical simulations showed that CO 2 adsorption was mainly influenced by electrostatic interactions, whereas O 2 adsorption was completely regulated by dispersion interactions. This distinction indicated that introducing polar oxygen functional groups at the edge of the carbon plane can significantly enhance the selectivity for CO 2 /O 2 adsorption. The difference in the adsorption energy between CO 2 and O 2 increased most noticeably after the carboxyl groups were introduced. The results of the adsorption experiments showed that oxygen-functionalization increased the CO 2 /O 2 selectivity of the carbon material under an atmosphere of multicomponent gases by more than 4.9 times. The carboxyl groups played a dominant role. Our findings might act as a reference for the selective adsorption of polar molecules over nonpolar molecules.