ARTICLE pubs.acs.org/JPCC
Synthesis, Growth Mechanism, and Electrochemical Properties of Hollow Mesoporous Carbon Spheres with Controlled Diameter Xuecheng Chen,*,† Krzysztof Kierzek,‡ Zhiwei Jiang,§ Hongmin Chen,^ Tao Tang,§ Malgorzata Wojtoniszak,† Ryszard J. Kalenczuk,† Paul K. Chu,*,^ and Ewa Borowiak-Palen† †
Institute of Chemical and Environment Engineering, West Pomeranian University of Technology, Szczecinul. Pulaskiego 10, 70-322 Szczecin, Poland ‡ Department of Polymer and Carbonaceous Materials, Wroclaw University of Technology, ul. Gdanska 7/9, 50344 Wroclaw, Poland § Changchun Institute of Applied Chemistry, Chinese Academy of Science, Changchun, China ^ Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China ABSTRACT: Hollow mesoporous carbon spheres with controllable diameters have been fabricated from core shell structured mesoporous silica sphere templates using chemical vapor deposition (CVD). By controlling the thickness of the silica shell, hollow carbon spheres with different diameters are obtained. The use of ethylene as the carbon precursor produces mesoporous graphitic hollow carbon spheres. The hollow carbon spheres have a relatively large degree of graphitization together with good meso-structural order and high specific surface area of 771 m2/g. The mechanism governing the formation of the hollow spheres is studied, and the importance of the surfactant (CTAB) is also clarified. CTAB accelerates the carbon deposition process, thus improving the product yield. These hollow carbon spheres that have good electrochemical properties are suitable for lithium ion batteries.
’ INTRODUCTION Future nanotechnology hinges on the ability to synthesize new nanomaterials possessing distinct structural and functional features.1,2 Among them, hollow nanospheres are unique and have attracted much research and industrial interest due to their special shape, low density, and large fraction of voids. Hollow nanospheres possess “tunable” void volume, excellent flow performance, and large surface area. The large internal volume provides a storage space or an artificial reaction “cell” that can serve many functions,3,4 and much can be learned from mesoporous nanostructures. Mesoporous carbon has been a big research topic because of its remarkable properties such as high specific surface area, large pore volume, low density, thermal conductivity, electrical conductivity, good chemical and mechanical stability, and great application potential to catalysts, electrodes, batteries, sensors, adsorbents in separation processes, gas storage materials, and templates for fabricating nanostructures. Furthermore, hollow carbon spheres with mesoporous shells possess more advantages in mass diffusion and transport than conventional mesoporous materials due to their larger pore, cavity volume, and spherical morphology.5 13 Several approaches have been developed to prepare hollow mesoporous carbon spheres. These hollow mesoporous carbon spheres are generally fabricated using sacrificial templates because this method allows control of the pore structure and morphology of the resulting carbon materials. There are two common ways to synthesize hollow mesoporous carbon spheres. r 2011 American Chemical Society
In the first technique, hard mesoporous templates are infiltrated with carbon precursors and then carbonized at a high temperature under nonoxidizing conditions to etch the templates and generate porous carbon. Hollow mesoporous aluminosilicate spheres and hard silica core/mesoporous silica shell spheres have been used as the templates to produce hollow mesoporous carbon spheres.14 24 Here, the carbon precursors are usually sucrose, furfuryl alcohol, and phenol formaldehyde resin, all of which are easy to carbonize under an inert gas.25 29 In 2002, Yoon and co-workers reported the fabrication of hollow carbon spheres with a mesoporous wall, and aluminum must be incorporated into the silicate framework before introduction of the carbon source. Since then, this method has been widely adopted.30 In 2006, Kleitz et. al used a spherical core shell structure (SiO2@ZrO2) as the template and furfuryl alcohol as the carbon source to produce the porous hollow carbon structure.31[ The second method is chemical vapor nanocasting in which the carbon source is usually styrene, acetonitrile, or benzene. All three are relatively easy to carbonize under an inert gas at a higher temperature.32 36 However, by using the CVD nanocasting method, only carbon spheres with large mean diameters (>500 nm) can be obtained. Synthesis of small carbon spheres (
