Investigation of the Mechanisms of CO<sub>2</sub>/O<sub>2</sub> Adsorption Selectivity on Carbon Materials Enhanced by Oxygen Functional Groups
Jiuyang Jia, Haiqian Zhao, Mingqi He, Zhonghua Wang, Zekun Sun, Xue Yang, Yu Qi, Zhibin Qu, Xinxin Pi, Feng Yao
Abstract
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.