Role of graphene in MnO2/graphene composite for catalytic ozonation of gaseous toluene

The degradation of gaseous toluene is of great significance to protect human health. In this work, a facile and environmentally friendly route for synthesis of different MnO2 loadings (14.2-94.8 wt.%) on graphene composites was developed through the direct redox reaction between graphene oxide and potassium permanganate at 160 degrees C for 12 h under hydrothermal condition. The elemental composition, crystal structure, and material properties of the MnO2/graphene samples were characterized using ICP-AES, XRD, TEM, FTIR spectroscopy, Raman spectroscopy, N-2 physisorption technique, and TG/DTA. The results show that the hydrothermal method is an effective way to prepare tightly anchored birnessite-type MnO2 on graphene. MnO2 nanoparticles were uniformly distributed throughout the surface of graphene nanosheets at 64.6 wt.% MnO2 loading, whereas aggregation or erosion of graphene sheets occurred at low or high loading of MnO2. The activities of graphene, MnO2, and the MnO2/graphene samples in catalytic ozonation of gaseous toluene were determined at 22 degrees C. The amount of MnO2 loaded on graphene showed a significant influence on the BET surface area, and the catalytic activity of the MnO2/graphene samples. The highest toluene degradation rate (7.89 x 10(-6) mol min(-1) g(-1)) over the 64.6 wt.% MnO2/graphene sample was attributed to the synergetic effect of graphene and MnO2 which was attributed to the tight connection between the active sites on graphene for adsorption of toluene and decomposition of ozone, and the MnO2 on graphene for decomposition of ozone to form atomic oxygen species. (C) 2014 Elsevier B.V. All rights reserved.