Graphene produced by thermally-altered coal:chemical structure evolution

As a kind of carbon material with excellent performance,graphene has a broad application prospect.China is rich in coal resources,and the research on the preparation of graphene using coal as raw material needs to be deepened continuously.Thermally-altered coal affected has high carbon content and high aromaticity,but its feasibility of preparing graphene is worth studying.Taking No.5 Coal seam of Shuoli Coal Mine in Huaibei Coalfield as the research object and takes three thermally-altered coals close to the magma intrusion as the feed coal.The preparation of coal-based graphene was by using the improved Hummers method.After graphitization of feed coals,the coal-based graphite was produced to coal-based graphene through oxidation,ultrasonic exfoliation,and reduction.Fourier Transform Infrared Spectroscopy (FTIR),Raman spectroscopy,and X-ray diffraction were used to analyze coal-based graphite,GO,and RGO one by one.The experimental results shows that the (002) d-spacing of the coal-based graphite is 0.338 1 nm.The molecular structure of GO contains carboxyl,hydroxyl,and epoxy groups.These functional groups fall off after reduction and form defects in the structure of the RGO.The characteristic absorption peaks of hydroxyl groups appear in both the coal-based graphite and RGO infrared spectrogram.The difference is that the hydroxyl group in the coal-based graphite comes from the residue left in the graphitization process,while the hydroxyl group in the RGO is the residue left in the incomplete reduction of GO.The results of Raman spectroscopy showed that ID/IG>1 of GO after reduction.It is caused by surface defects formed by the detachment of epoxy groups on the graphene sheet surface during the reduction process.The layers of RGO prepared by thermally-altered coals are 4.29,3.97,and 4.31 respectively,all of which belong to few-layered graphene.Thermally-altered coal can be used as a source material for the preparation of graphene.