A Temperature-Controlled Plasma Strategy Toward High-Purity Submicron Graphene

In many practical applications, submicron graphene achieves better performance than large-sized graphene due to its good dispersibility, abundant edge groups, and large specific surface area. However, current preparation methods for submicron graphene, including mechanical grinding and subsequent size fractionation, are inefficient. Moreover, in the preparation process, metallic impurities are inevitably introduced, which hinders the application of graphene in electronic devices. Herein, we propose a novel temperature-controlled plasma strategy to prepare high-purity submicron few-layer graphene from reduced graphene oxide (RGO) films with hydrogen arc plasma. In this strategy, graphene with an average lateral size of 434.4 nm and a C/O ratio of 42.6 was obtained. The contents of major metallic impurities (Fe, Cr, Ni, Mn and etc.) were all less than 5 ppm. Furthermore, the morphology control and purification mechanisms were explored. Plasma temperature was adjusted effectively by an externally introduced cooling gas flow to be suitable for the intercalation of hydrogen atoms, which led to the exfoliation of RGO films and the chemical edge etching of graphene sheets. Meanwhile, the strong electric field of arc plasma was utilized to separate the ionized metallic impurities from the graphene product. This work would promote the development of plasma technologies in graphene preparation.