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

doi:10.1038/s41467-021-25640-1

Regulation of functional groups on graphene quantum dots directs selective CO₂ to CH₄ conversion

Nat Commun. 2021 Sep 6;12(1):5265. doi: 10.1038/s41467-021-25640-1.

Authors

Tianyu Zhang^#¹, Weitao Li^#², Kai Huang^#³, Huazhang Guo², Zhengyuan Li¹, Yanbo Fang⁴, Ram Manohar Yadav⁵, Vesselin Shanov^{1

4}, Pulickel M Ajayan⁵, Liang Wang⁶, Cheng Lian⁷, Jingjie Wu⁸

Affiliations

¹ Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH, USA.
² Institute of Nanochemistry and Nanobiology, Shanghai University, Shanghai, China.
³ State Key Laboratory of Chemical Engineering, School of Chemical Engineering, East China University of Science and Technology, Shanghai, China.
⁴ Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH, USA.
⁵ Department of Materials Science and NanoEngineering, Rice University, Houston, TX, USA.
⁶ Institute of Nanochemistry and Nanobiology, Shanghai University, Shanghai, China. wangl@shu.edu.cn.
⁷ State Key Laboratory of Chemical Engineering, School of Chemical Engineering, East China University of Science and Technology, Shanghai, China. liancheng@ecust.edu.cn.
⁸ Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH, USA. jingjie.wu@uc.edu.

^# Contributed equally.

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 CO₂ to high-value chemicals. Cu is the only known metal catalyst that can convert CO₂ 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 CO₂ to CH₄ conversion with simultaneous high selectivity and production rate. The electron-donating groups facilitate the yield of CH₄ from CO₂ electro-reduction while electron-withdrawing groups suppress CO₂ electro-reduction. The yield of CH₄ 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 -NH₂ functional group could achieve Faradaic efficiency of 70.0% for CH₄ at -200 mA cm^-2 partial current density of CH₄. The superior yield of CH₄ 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 CO₂ electro-reduction.