One-step synthesis of fluorinated graphene (FG) from natural coaly graphite (NCG) and the influence of NCG on the FG

Abstract

Preparation of cost-effective fluorinated graphene (FG) has been a great challenge due to the expensive starting materials. In this article, natural coaly graphite (NCG) samples, collected at various distances from the intrusion, were used as starting materials to synthesis FG via a one-step hydrothermal process in hydrofluoric acid. The influence of NCG precursors on the resultant FG was investigated systematically. Not only the poorly ordered graphite layer with large interlayer distance and the structural defects, but also the organic oxygen and pyridinic groups in NCG promote the fluorination. For well crystallized NCG samples, the parameters of organic oxygen ratio (O/C), graphitization degree (DOG) or defect level (ID/IG) of the NCG were reliable indicators of fluorination ability. For poorly crystallized NCG, the maximum fluorination of the resultant FG is as high as 34.50 % benefitting from the rich carbonyl groups of poorly crystallized NCG. In addition, the ash content is reduced to 0.04–2.41 % in FG samples from 13.58 to 28.05 % in NCG samples, and bulk NCG samples could be stripped into nanosheets of a few layers thickness simultaneously, which are respectively controlled by the ash content and crystalline order of NCG. Such findings provide crucial guidance for industry to design FG with a predicable fluorination level through selection of a specific NCG material. Most importantly, FG synthesized from NCG is facile, low-cost and highly scalable, which will drastically improve the value of currently ignored NCG.