▎ 摘　　要

The carbothermal and graphenothermal reduction of metal oxide and graphite or graphene systems are critical for obtaining pure metals and designing new energy materials. However, the nano-level differences between these processes have not been investigated in detail. Herein, we investigate the relationship between crystalline growth and chemical reduction during the heat-treatment of reduced graphene oxide (RGO) and NiO nanoparticles. The heat-treated RGO/NiO mixtures exhibit complex interactions. Below a critical NiO concentration, the crystalline growth of RGO and NiO take precedence. Above this threshold, drastic Ni formation occurs by the chemical reduction of NiO. This demonstrates a concentration-dependent competitive relationship between chemical reduction and crystalline growth. Two factors require further study, namely, the low-dimensional shape/contact-dependent chemical reactivity between RGO and NiO, and the thermodynamic size-dependent driving force for crystalline growth of individual RGO and NiO crystals.