Catalyst-Free Growth of Three-Dimensional Graphene Flakes and Graphene/g‑C<sub>3</sub>N<sub>4</sub> Composite for Hydrocarbon Oxidation

Mass production of high-quality graphene flakes is important for commercial applications. Graphene microsheets have been produced on an industrial scale by chemical and liquid-phase exfoliation of graphite. However, strong-interaction-induced interlayer aggregation usually leads to the degradation of their intrinsic properties. Moreover, the crystallinity or layer-thickness controllability is not so perfect to fulfill the requirement for advanced technologies. Herein, we report a quartz-powder-derived chemical vapor deposition growth of three-dimensional (3D) high-quality graphene flakes and demonstrate the fabrication and application of graphene/g-C<sub>3</sub>N<sub>4</sub> composites. The graphene flakes obtained after the removal of growth substrates exhibit the 3D curved microstructure, controllable layer thickness, good crystallinity, as well as weak interlayer interactions suitable for preventing the interlayer stacking. Benefiting from this, we achieved the direct synthesis of g-C<sub>3</sub>N<sub>4</sub> on purified graphene flakes to form the uniform graphene/g-C<sub>3</sub>N<sub>4</sub> composite, which provides efficient electron transfer interfaces to boost its catalytic oxidation activity of cycloalkane with relatively high yield, good selectivity, and reliable stability.