石墨氧化和再还原过程中结构的演变与表征研究

The structural layer of graphite is the thinnest two-dimensional nanostructure unit in minerals. Treated by oxidation, graphite will be changed into graphite oxide from which the graphene oxide can be produced by stripping and dispersing. Afterwards, graphene can be obtained by deoxidizing the graphene oxide. Since the oxidation and reduction degree greatly affecting the size, physicochemical properties and applications of graphene oxide and graphene, it is necessary to make a further study on the evolution and characterization of structure during the process of graphite oxidation and reduction. The compositions, structures, spectrum and properties of graphitic products with different oxidation and reduction levels will be characterized by various kinds of effective analysis and test measurement. Varieties, distributions, including in-plane distribution, out-of-plane distribution and density distribution, and regularity of oxygen functional groups on the carbon atom plane of the graphitic products will be discussed. The quantitative variations of compositions, structures, spectroscopic parameters and properties of products with different oxidation-reduction levels will be clarified, which will be reasonably related with the crystal chemistry of various graphite minerals.Combining the theoretical calculations, the mechanism about structural evolution will be revealed, which including coordiantion and arrangement of functional groups in and out of plane of carbon hexagons,interlayer spacing, and two-dimensional periodic structures during the process of oxidation-reduction. As a result, the evolution model of two- and three- dimensional structures in structural layer will be built. This research proposal has theoretical and practical significant for the crystal chemistry of graphite mineral and the novel nanostructure of graphite materials.

石墨结构层是矿物中最薄的二维纳米单元。采用氧化处理将石墨转化为氧化石墨，经剥离分散获得氧化石墨烯，再经还原获得石墨烯。基于氧化和还原程度对氧化石墨烯与石墨烯片径和理化性能及用途的重要影响，对石墨氧化和再还原过程中结构的演变与表征进行深入研究。采用有效分析测试手段对不同氧化和还原程度的石墨产物的成分、结构、谱学和性能进行表征。研究氧化石墨及其剥离和再还原产物碳原子面上含氧官能团的接合种类和分布（面内、面外、密度）与规律性；随氧化－还原程度的不同产物在成分、结构、谱学参数和性能上的定量变化规律及其与不同产地石墨矿物晶体化学特征之间的联系；与理论计算相结合，揭示在氧化和再还原过程中碳原子层面内外官能团的配位、排布及层间距、二维结构周期性的变化规律和结构演化的内在机制；建立石墨氧化－还原过程中结构层二维和三维结构的演变模型。对石墨矿物晶体化学和新型纳米结构石墨材料的研究具有重要的理论和实际意义。

研究了不同产地石墨的矿物学特征；石墨在氧化和再还原过程中产物结构、性能的演变规律及机理；建立了石墨氧化－还原过程中三维结构的演变模型。.所采集样品为晶质和微晶石墨两种；晶质石墨疏水性强，隐晶质石墨亲水性强；晶质和微晶石墨氧化后结构层均接有含氧官能团，但微晶石墨比晶质石墨氧化后含有更多的COOH，C-OH和更少的C-O-C。.石墨氧化过程中，产物⊥c和⊥a-b轴面网间距和官能团种类、含量出现阶段性变化；π键共轭体系破坏，禁带宽度增加，导电性降低；样品平均晶粒尺寸减小，缺陷含量增多，无序度增大。在相同氧化条件下，晶质石墨制备的氧化石墨较微晶石墨制备的氧化石墨更易剥离成氧化石墨烯；增加分散溶剂的pH值可提高低氧化程度氧化石墨样品在溶剂中的剥离分散性；氧化石墨烯结构中π体系共轭区域大小及共轭程度的强弱，随氧化石墨氧化程度的增加，呈依次减小的规律性变化；氧化石墨烯成膜过程中在氢键力作用下，氧化石墨烯片层⊥c轴重新堆叠，结构趋于有序。.氧化石墨烯还原过程中，含氧官能团含量随还原剂用量增加而逐渐减少，但含氧官能团并不能完全去除；π键共轭体系恢复，碳碳键长收缩，d100、d110减小，禁带宽度减小，导电性增强；样品平均晶粒尺寸减小，缺陷含量增多；在成膜过程中碳层结构上残留的含氧官能团通过氢键的方式键合，形成二维叠成凝聚体，样品有序度降低，无序度增加。不同还原方法制备的石墨烯，碳-键长及收电性存在一定差异，经化学还原制备的石墨烯碳-键长最小；水热还原制备的石墨烯电阻率较低；化学还原氧化石墨烯电阻率较大。.氧化石墨烯的结构及性质的计算研发现，石墨烯为零带隙的半金属；氧化石墨结构中含氧官能团的最佳排布模式为：含氧官能团处于碳层平面两侧相邻位置；结构中羟基和环氧基都对氧化石墨烯电子结构起着显著的调控作用，且环氧官能团相对于羟基官能团对禁带宽度影响较大。.本项目的研究成果对石墨矿物晶体化学和石墨烯材料的研究具有重要的理论和实际意义。