流化床反应器中石墨烯宏观材料的可控制备及其应用

Graphene has extraordinary electric and thermal conductivity and mechanic property, which gives rise to many promising applications in fabracting electronic devices, electrodes or material reinforcement. Mass production at low cost is crucial to the applications using graphene as a bulk material. Reduction of graphite oxide almost is the only mehtod for scalable synthesis of graphene bulk materials at low cost. However, the graphene obtained by this approach lacks control of the number of graphene layers and exhibits deteriorated transport properties due to the presence of oxygen-containing functional groups and structural defects formed during the vigorous exfoliation and oxidation processes.Recently, chemical vapour deposition (CVD) synthesis of high quality graphene with well-controlled layer number on metal films supported by substrates have been developed. However, due to the limited area of the metal films, it is difficult to realize mass production of graphene bulk materias by this method. In this project, we aim to develop a CVD synthesis of graphene bulk materials using templates, which have powdered morphologies and can be used in a fluidized-bed reactor to realize the mass production of graphene bulk materials. We will focus on the controllable preparation of templates, control of the reaction conditions and characterization of the products, in order to provide a new approach to the mass production of graphenen bulk materials with well-controlled structures and low cost. On the base of the CVD　mass production, applications of the as-produced graphene in electrodes of lithium ion batteries and gas adsorption, storage or separation will be explored, which is expected to obtain fruitful results with innovation and practical values.

石墨烯具有优良的导电、导热和力学性能，在构造电子元件、用于制备电极和增强材料等方面有良好的应用前景。低成本大批量制备对采用石墨烯作为宏观材料的应用意义重大，氧化石墨还原法几乎是目前唯一能够低成本大批量制备石墨烯宏观材料的方法，但它存在难以精确控制石墨烯层数、强氧化还原过程造成导电性能变差等不足。化学气相沉积（CVD）法可较容易地在金属薄膜上制备结构可控、导电性良好的石墨烯，但金属薄膜表面积受限，难以批量制备石墨烯宏观材料。本课题拟发展一种模板CVD法制备石墨烯的工艺，采用宏观上呈粉末状态的模板剂可方便地在流化床反应器中实现石墨烯宏观材料的批量制备；重点研究模板剂的可控制备、反应条件控制和产品性能表征，以获得低成本大批量制备结构可控石墨烯宏观材料的新工艺。采用上述石墨烯产品，我们将初步探索其在锂离子电池电极、气体吸附存储分离等方面的应用，有望取得具有较高创新性和实用价值的成果。

石墨烯是一种新型薄层二维材料，具有高达2620 m2/g的比表面积、极佳的导电导热率和较高的机械强度，因而在导电导热添加材料、电极材料、吸附材料等方面具有应用潜力。但是，石墨烯的片层彼此容易堆积团聚，不利于石墨烯的批量制备和实际应用；常见的石墨烯批量制备方法中，氧化还原石墨法得到的石墨烯存在较多结构缺陷，导电性显著下降。针对以上问题，本项目采用气相化学沉积（CVD）法批量制备石墨烯，与常规的CVD法中采用铜箔作为基板不同，我们采用微观上为片层状、宏观上为粉末状的MgO作为模版，通过CH4高温裂解，在MgO片层表面生长石墨烯；由于MgO模版为多孔片层，生成的石墨烯具有表面褶皱和柱撑结构，因此不易团聚，比表面积可稳定保持在2000 m2/g；进一步，我们在气固流化床反应器中实现了多孔石墨烯的批量制备。为了调控石墨烯的表面性状和结构特征，我们还进一步制备了多孔石墨烯-碳纳米管复合材料和掺杂多孔石墨烯，为不同类型的应用提供了具有不同特点的多孔石墨烯。.在批量制备的基础上，我们考察了CVD法制备的多孔石墨烯在几个不同领域内的应用性能：1）多孔石墨烯可以直接用作高容量锂离子电池负极材料，其中硫氮双掺杂的多孔石墨烯的比容量可达3523 mAh/g （50 mA/g电流下）；2）多孔石墨烯与过渡金属氧化物的复合材料可以用作高性能锂离子电池负极材料，我们考察了Co3O4-多孔石墨烯和Fe2O3-多孔石墨烯两种复合材料；3）多孔石墨烯具有较高的甲烷、CO2吸附性能，多孔石墨烯负载Ni纳米颗粒表现出较高的H2吸附能力。.总的看来，本项目的实施有力推进了多孔石墨烯CVD法批量制备和应用的发展，具有重要的理论和应用价值。