基于化学气相沉积技术的粉体石墨烯的制备及能源领域应用

Chemical vapor deposition design of graphene powders toward energy applications

化学气相沉积技术(chemical vapor deposition,CVD)因其产物设计性强、反应途径灵活、层数均匀可控、衬底种类多样、批量化高品质制备等特点而广受关注.本文以CVD制备石墨烯为出发点,归纳利用模板法和非模板法合成具有特定形貌的高品质粉体石墨烯材料,其具有高电导率、大比表面积和良好的分散性.进一步地,基于CVD方法合成的粉体石墨烯,对其在能量存储领域的应用展开阐述.CVD技术所制备的粉体石墨烯在储能应用领域中展现出的巨大潜力,使其有望成为助力高能量长循环储能器件的理想材料.

Graphene,sp^2-bonded carbon atoms being regularly packed into a two-dimensional(2D)honeycomb structure,has attracted wide attentions,owing to its excellent electrical(the carrier mobility^10^5 cm^2V^–1s^–1),mechanical(~1.1 TPa),optical(the transparency of single layer graphene is about 97.7%)and thermal(the thermal conductivity^5000 W m^–1K^–1)properties.These unique properties make it suitable for use in transparent conductivity electrodes,field-electric transistors,photodetectors,light-emitting diodes,energy storage materials and many other areas.In particular,in comparison with the conventional 2 D graphene films,three-dimensional graphene powders have presented great potentials in energy related applications because of their controllable structures,high specific surface areas and excellent electrical conductivity.There are mainly two synthetic routes for preparing graphene powder materials with specific structures and morphologies.One route deals with the preparation of graphite oxide sheets,then throughout chemical reduction process to obtain reduced graphene oxide.Although this method enables the realization of mass production of graphene powders with a relatively low cost,the materials obtained show quite poor crystal quality with high defect density,thereby greatly limiting the fast electron transport in high-energy-density and high-power-density energy storage devices.The other route is the chemical vapor deposition(CVD)growth of graphene powders with/without template-direction.Taking advantage of the CVD method,the crystal quality and electrical conductivity properties of graphene powders can be obviously improved.Meanwhile,the templates used during growth process can effectively control the morphologies of graphene powders,realizing graphene materials with high specific surface areas.Moreover,by selecting proper carbon sources or other reaction precursors,graphene powders with heteroatomic(N,B,P,S)doping can be achieved.This route facilitates mass production of high-crystal quality graphene with specific architecture,controllable layer numbers and effective heteroatomic doping,thus greatly promoting the application of graphene-based energy related devices.Herein,this review highlights the recent advances in the chemical vapor deposition design of graphene materials and their related energy applications.Firstly,a brief introduction with respect to the CVD synthesis of graphene powders,including template-directed growth and template-free growth is provided.Taking use of metal particles,oxide powders,chloride particles and biomineral materials as the growth substrates(templates),graphene powders with circular,cubic or other specific morphologies have been successfully synthesized.The growth mechanisms of graphene on metal substrates and non-metal substrates are also probed.Upon summarizing the direct growth methods of graphene powders by CVD and the related growth mechanisms,energy applications pertaining to batteries(lithium-ion batteries,lithium-sulfur batteries,sodium-ion batteries,potassium-ion batteries),supercapacitors,printed energy storage devices and catalysts are further highlighted.Because of the unique characteristics of high electrical conductivity,large accessible surface area,and excellent electrochemical properties,graphene-based materials exhibit high performances in energy-related applications.Finally,further development and challenges of the CVD graphene materials in this emerging field are proposed.