Acta Phys. -Chim. Sin. ›› 2018, Vol. 34 ›› Issue (8): 938-944.doi: 10.3866/PKU.WHXB201801263

Special Issue: Green Chemistry

• ARTICLE • Previous Articles     Next Articles

Catalytic Electroreduction of CO2 to C2H4 Using Cu2O Supported on 1-Octyl-3-methylimidazole Functionalized Graphite Sheets

Hui NING1,2,Wenhang WANG1,Qinhu MAO1,Shirui ZHENG1,Zhongxue YANG1,Qingshan ZHAO1,Mingbo WU1,*()   

  1. 1 State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Qingdao 266580, Shandong Province, P. R. China
    2 CAS Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, P. R. China
  • Received:2018-01-03 Published:2018-04-03
  • Contact: Mingbo WU E-mail:wumb@upc.edu.cn
  • Supported by:
    The project was supported by the CAS Key Laboratory of Carbon Materials, China(KLCMKFJJ1706);the National Natural Science Foundation of China(51372277);the National Natural Science Foundation of China(51572296);the National Natural Science Foundation of China(U1662113)

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Abstract:

The electrocatalytic reduction of CO2 to C2H4 is a topic of great interest. It is known that the preparation of efficient catalysts for this transformation is the key factor that determines the yield of C2H4. In this study, we prepared 1-octyl-3-methylimidazole functionalized graphite sheets (ILGS) in a facile manner by the electro-exfoliation of pure graphite rod in an aqueous solution of 1-octyl-3-methylimidazolium chloride (OmimCl : H2O = 1 : 5, V/V) at 10 V. They were then dispersed in an aqueous solution of copper chloride and sodium citrate. Subsequent reduction with sodium borohydride led to the formation of a composite comprised of cuprous oxide supported on Omim-functionalized graphite sheets (Cu2O/ILGS). This composite was found to be an efficient catalyst for the electroreduction of carbon dioxide to ethylene. The as-made materials were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction (XRD). The TEM images showed that the ILGS were composed of multiple layers of graphene. The XRD pattern and Raman spectrum indicated that the surface of the ILGS possessed several defects. In the electro-exfoliation process, the defects in the ILGS were modified in situ by covalent bonding with Omim groups, which was also confirmed by XPS. The Cu2O nanoparticles with an average diameter of 5 nm were uniformly distributed on the surface of the ILGS because the Omim groups grafted to the graphite sheets acted as anchors and prevented their aggregation by the steric effect. The electrocatalytic activities of Cu2O/ILGS for CO2 reduction were measured at different voltages in 0.1 mol L–1 KHCO3 aqueous solution under ambient temperature and pressure. These experiments showed that the catalytic performance of the Cu2O/ILGS composite was determined by cuprous oxide, while the ILGS displayed nearly no catalytic activity in the electroreduction of carbon dioxide. The faradaic efficiency of hydrogen and carbon dioxide reduction products changed with the reaction time because of the reduction of Cu2O to Cu under the electroreduction conditions. The faradaic efficiency of ethylene was ~14.8% at –1.3 V (versus reversible hydrogen electrode). The performance of Cu2O/ILGS in the catalytic electroreduction of carbon dioxide was attributed to the stabilization of the Cu2O nanoparticles by the nest-like microstructures in the Cu2O/ILGS composite.

Key words: Cu2O, Graphite sheets, CO2 reduction, Ethylene, Ionic liquids