热接触变质煤制备石墨烯:化学结构演化

作为具有优异性能的碳材料,石墨烯应用前景广阔。我国煤炭资源储量丰富,以煤为原料,探讨制备石墨烯的研究需不断深化。受岩浆影响的热接触变质煤具有高碳含量、高芳香度等特点,但其制备石墨烯的可行性值得研究。以淮北煤田朔里煤矿5号煤层为研究对象,采集3个靠近岩浆侵入体的热接触变质煤为原料。煤基石墨烯的制备采用改进Hummers法,原煤经石墨化后,通过氧化、超声剥离、还原成石墨烯。采用傅里叶变换红外光谱(FTIR)、拉曼光谱和X射线衍射对煤基石墨、氧化石墨烯和还原氧化石墨烯逐一进行分析。结果表明:3个样品制得的煤基石墨的(002)晶面间距均为0.3381 nm。氧化石墨烯的分子结构中含有羧基、羟基和环氧基,在还原后这些官能团脱落并形成了还原氧化石墨烯结构中的缺陷。煤基石墨和还原氧化石墨烯的红外光谱都出现了羟基的特征吸收峰,区别在于煤基石墨中的羟基为石墨化过程中所残留的,而还原氧化石墨烯中的羟基则是氧化石墨烯未彻底还原所残留的。拉曼光谱分析的结果表明氧化石墨烯在还原后ID/IG(D峰与G峰强度比)>1,为还原过程中石墨烯片层表面的环氧基脱落形成的面缺陷所导致。由朔里热接触变质煤所制备出的还原氧化石墨烯的平均层数分别为4.29、3.97和4.31,均属少层石墨烯,热接触变质煤可作为制备石墨烯的原料。

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 re?sources,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 0.3381 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 differ?ence 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.