A few-layer graphene-graphene oxide composite containing nanodiamonds as metal-free catalysts.

We report a high yield exfoliation of few-layer-graphene (FLG) with up to 17% yield from expanded graphite, under 5 h sonication time in water, using graphene oxide (GO) as a surfactant. The aqueous dispersion of GO attached FLG (FLG-GO), with less than 5 layers, is used as a template for further decoration of nanodiamonds (NDs). The hybrid materials were self-organized into 3D-laminated nanostructures, where spherical NDs with a diameter of 4-8 nm are homogeneously distributed on the surface of the FLG-GO complex (referred to as FLG-GO@NDs). It was found that GO plays a dual role, it (1) mediated exfoliation of expanded graphite in aqueous solution resulting in a FLG-GO colloid system, and (2) incorporated ND particles for the formation of composites. A high catalytic performance in the dehydrogenation of ethyl- benzene on FLG-GO@ND metal-free catalyst is achieved; 35.1% of ethylbenzene conversion and 98.6% styrene selectivity after a 50 h reaction test are observed which correspond to an activity of 896 mmol_ST g_catalyst ¹ h^_1, which is 1.7 and 5 times higher than those of the unsupported NDs and traditional catalysts, respectively. The results demonstrate the potential of the FLG-GO@ND composite as a promising catalyst for steam-free industrial dehydrogenation applications. [ABSTRACT FROM AUTHOR]