Zhuxian Yang

Zeolitic imidazolate framework materials: recent progress in synthesis and applications

Zeolitic imidazolate frameworks (ZIFs) represent a new and special class of metal organic frameworks comprised of imidazolate linkers and metal ions, with structures similar to conventional aluminosilicate zeolites. Their intrinsic porous characteristics, abundant functionalities as well as exceptional thermal and chemical stabilities have led to a wide range of potential applications for various ZIF materials. Explosive research activities ranging from synthesis approaches to attractive applications of ZIFs have emerged in this rapidly developing field in the past 5 years. In this review, the development and recent progress towards different synthesis strategies to generate both powder and membrane/film-based ZIF materials are analysed and summarised. Their attractive and potential applications in gas separation, catalysis, sensing and electronic devices, and drug delivery in the past years are discussed and reviewed. In addition, the prospects and potential new development of ZIF materials are presented.

Porous carbon-based materials for hydrogen storage: advancement and challenges

The development of highly efficient hydrogen storage materials is one of the main challenges that must be tackled in a widely expected hydrogen economy. Physisorption in porous materials with high surface areas and chemisorption in hydrides are the two main options for solid state hydrogen storage, and both options possess their inherent advantages and drawbacks. In this work, recent progress towards porous carbon-based materials for hydrogen storage is analyzed and reviewed. The hydrogen storage performance of plain porous carbons, metal-supported porous carbons and porous carbons confined hydrides is summarized. Some strategies for effectively controlling the hydrogen storage capacity and tuning the hydrogen adsorption enthalpy for porous carbon materials via appropriate manipulation of surface area, pore volume and pore size are discussed in detail. The new development of porous carbon-based materials for hydrogen storage is particularly emphasized.

Electrical Double-Layer Capacitance of Zeolite-Templated Carbon in Organic Electrolyte

Downlo Electrical Double-Layer Capacitance of Zeolite-Templated Carbon in Organic Electrolyte C. Portet,* Z. Yang, Y. Korenblit, Y. Gogotsi,** R. Mokaya, and G. Yushin A. J. Drexel Nanotechnology Institute and Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA School of Chemistry, University of Nottingham, Nottingham NG7 2RD, United Kingdom School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

Three dimensional (3D) flexible graphene foam/polypyrrole composite: towards highly efficient supercapacitors

Polypyrrole (PPY) functionalized 3 dimensional (3D) graphene foam (GF) with remarkable electrochemical performance has been synthesized in this work. The resulting 3D PPY–GF electrode is free standing and hence was used directly as a working electrode without using any binder or carbon additives. The unique features of the PPY–GF composites such as their hierarchically flexible 3D network, and high conductivity of p-doped PPY, afforded PPY–GF electrodes with enhanced pseudocapacitive properties. Under optimal conditions, a maximum specific capacitance of 660 F g−1, specific energy of 71 W h kg−1, comparable to battery performance, and a specific power of 2.4 kW kg−1 (at 0.5 mA) were obtained. Both GF and PPY–GF electrodes exhibited an excellent cycle life and retained almost 100% of their initial capacitances after 10 000 and 6000 charge–discharge cycles, respectively. This highly enhanced stability is attributed to the significant impact of the GF density on the flexibility of the electrode, and the hierarchical pore structures which provided short effective pathways for ion and charge transport and stayed unchanged after thousands of cycles. The PPY–GF pore size varies from a few nm for small pores to a hundred μm for macropores.

Designing 3D graphene networks via a 3D-printed Ni template

It is highly desirable to design and control the properties of 3D graphene networks with preferred shapes, lengths, diameters of the trusses so as to add new functionalities. Hereby, we demonstrate a conceptual design and the practical synthesis of periodic 3D graphene networks via CVD using a 3D-printed Ni scaffold as the template.

Synthesis of hollow spherical mesoporous N-doped carbon materials with graphitic framework

Mesostructured carbon hollow spheres were prepared via a chemical vapour deposition (CVD) nanocasting route which utilized mesoporous silica SBA-15 spheres as sacrificial solid template and acetonitrile as carbon source. The hollow spheres were obtained when CVD derived silica/carbon composites were subjected to silica etching in hydrofluoric (HF) acid. The use of acetonitrile as carbon source resulted in N-doped (CNx type) materials with nitrogen content of up to 7.8 wt%. The mesostructured carbon hollow spheres have high surface area and pore volume (up to 780 m2/g and 0.66 cm3/g respectively) and in addition exhibit high levels of graphitization in the pore walls. The pore size of the hollow spheres was varied (between 2 and 5 nm) by changing the nature of spherical SBA-15 silica used as template.

Porous N-doped carbon with various hollow-cored morphologies nanocast using zeolite templates via chemical vapour deposition

The synthesis of porous nitrogen-doped carbon materials with various hollow-cored morphologies has been achieved via a chemical vapour deposition (CVD) route that utilizes acetonitrile as carbon source and zeolites as solid template. The morphology of the hollow-cored carbons is controlled by the choice of solid template (Zeolite β or Silicalite-I) and carbonization conditions (i.e., CVD temperature). In particular, high surface area (up to 2200 m 2 /g) hollow hexagonal shells of N-doped carbon that possess graphitic characteristics have been obtained using zeolite β as the solid template. In addition graphitic forms of hollow cubic, rectangular, and spherical porous carbon materials have been synthesized using silicalite-I as the solid template.

A generic method to synthesise graphitic carbon coated nanoparticles in large scale and their derivative polymer nanocomposites

A versatile Rotary Chemical Vapour Deposition (RCVD) technique for the in-situ synthesis of large scale carbon-coated non-magnetic metal oxide nanoparticles (NPs) is presented, and a controllable coating thickness varying between 1–5 nm has been achieved. The technique has significantly up-scaled the traditional chemical vapour deposition (CVD) production for NPs from mg level to 10 s of grams per batch, with the potential for continuous manufacturing. The resulting smooth and uniform C-coatings sheathing the inner core metal oxide NPs are made of well-crystallised graphitic layers, as confirmed by electron microscopy imaging, electron dispersive spectrum elemental line scan, X-ray powder diffractions and Raman spectroscopy. Using nylon 12 as an example matrix, we further demonstrate that the inclusion of C-coated composite NPs into the matrix improves the thermal conductivity, from 0.205 W∙m−1∙K−1 for neat nylon 12 to 0.305 W∙m−1∙K−1 for a 4 wt% C-coated ZnO composite, in addition to a 27% improvement in tensile strength at 2 wt% addition.

Novel graphitic carbon coated IF-WS2 reinforced poly(ether ether ketone) nanocomposites

Unique high performance thermoplastic PEEK ternary nanocomposites reinforced by nano graphitic carbon coated IF-WS2 (inorganic fullerene-like tungsten disulphide) have been prepared and their structures have been characterised by electron microscopy imaging, electron dispersive spectrum elemental and X-ray diffraction scanning. The IF-WS2@C–PEEK composites exhibit impressive improvements in both their mechanical and thermal properties, with an extraordinary 54% enhancement in the ultimate tensile strength at 2 wt% and a nearly 235% increase in thermal conductivity at 8 wt%. In addition, they also show an increase in decomposition temperature (over 50 °C) with higher IF-WS2@C contents. Further investigation reveals the activation energies estimated by the Kissinger method to be 61 and 97 kJ mol−1 for neat PEEK and IF-WS2@C–PEEK, respectively. This is ascribed to the enhanced dispersion ability and better interface bonding between the PEEK matrix and IF-WS2@C nanoparticles, which for the first time has been investigated by FTIR and XPS analysis. These significantly improved properties will no doubt expand the applications of the PEEK-based nanocomposites.

Preparation of versatile silica/carbon nanocomposites via carbonization of ethyl-bridged periodic mesoporous organosilica

Mesoporous silica/carbon composites may be obtained from periodic mesoporous organosilica (PMO) mesophases via pyrolysis under argon flow at 800 - 950°C. The composite materials are mesostructurally well ordered with surface area of ca. 820 m 2 /g and pore volume of 0.4 cm 3 /g. Calcination of the composites, at 550°C for 8 h in air, generates well ordered mesoporous silicas with surface area > 700 m 2 /g, while nanoporous carbons with surface area > 500 m 2 /g and which exhibit graphitic characteristics are generated via silica etching of the composites. The silica/carbon composites, mesoporous silicas and nanostructured carbons retained the morphology of the PMO mesophases.