Regulation of functional groups on graphene quantum dots directs selective CO2 to CH4 conversion
Tianyu Zhang, Weitao Li, Kai Huang, Huazhang Guo, Zhengyuan Li, Yanbo Fang, Ram Manohar Yadav, Vesselin Shanov, Pulickel M. Ajayan, Liang Wang, Cheng Lian, Jingjie Wu
Abstract
Abstract A catalyst system with dedicated selectivity toward a single hydrocarbon or oxygenate product is essential to enable the industrial application of electrochemical conversion of CO 2 to high-value chemicals. Cu is the only known metal catalyst that can convert CO 2 to high-order hydrocarbons and oxygenates. However, the Cu-based catalysts suffer from diverse selectivity. Here, we report that the functionalized graphene quantum dots can direct CO 2 to CH 4 conversion with simultaneous high selectivity and production rate. The electron-donating groups facilitate the yield of CH 4 from CO 2 electro-reduction while electron-withdrawing groups suppress CO 2 electro-reduction. The yield of CH 4 on electron-donating group functionalized graphene quantum dots is positively correlated to the electron-donating ability and content of electron-donating group. The graphene quantum dots functionalized by either –OH or –NH 2 functional group could achieve Faradaic efficiency of 70.0% for CH 4 at −200 mA cm −2 partial current density of CH 4 . The superior yield of CH 4 on electron-donating group- over the electron-withdrawing group-functionalized graphene quantum dots possibly originates from the maintenance of higher charge density of potential active sites (neighboring C or N) and the interaction between the electron-donating group and key intermediates. This work provides insight into the design of active carbon catalysts at the molecular scale for the CO 2 electro-reduction.