Controllable one-step, chemical-free synthesis of graphene forests with graphene quantum dots via hydrogen-assisted thermal decomposition of SiC

Simultaneous, controllable synthesis of large-surface-area graphene and graphene quantum dots (GQDs) typically relies on multi-step, chemically intensive routes. Here we report a one-step, chemical-free approach based on low-pressure hydrogen-assisted thermal decomposition of silicon carbide (SiC), without supplying any external carbon precursor, which yields graphene forests (GFs) decorated with GQDs in a single heating process. Notably, the morphology is dominantly controlled by the hydrogen flow rate (H), with thermal energy (T) acting as an auxiliary parameter that influences the extent of growth. This enables systematic modulation of the relative population between GQDs and graphene nanosheets (GNSs), accompanied by reconstruction of the SiC surface from an initially flat morphology to a characteristic bumpy topology. Density functional theory (DFT) calculations provide atomistic evidence that hydrogen plays dual roles in anisotropic substrate etching and chemically promoted lateral carbon attachment. These effects rationalize the observed transition from GQD-dominant to GNS-dominant forests. This platform offers a potentially scalable, chemical-free route to structurally tunable carbon nanomaterials.