Graphitized hollow carbon spheres and yolk-structured carbon spheres fabricated by metal-catalyst-free chemical vapor deposition

Hard-sphere-templating method has been widely used to synthesize hollow carbon spheres (HCSs), in which the spheres were firstly coated with a carbon precursor, followed by carbonization and core removal. The obtained HCSs are generally amorphous or weakly graphitized (with the help of graphitization catalysts). In this work, we report on the fabrication of graphitized HCSs and yolk-shell Au@HCS nanostructures using a modified templating method, in which smooth, uniform graphene layers were grown on SiO₂ spheres or Au@SiO₂ nanoparticles via metal-catalyst-free chemical vapor deposition (CVD) of methane. Our work not only provides a new method to fabricate high-quality, graphitized HCSs but also demonstrates a reliable approach to grow quality graphene on oxide surfaces using CVD without the presence of metal catalysts.