Carbon nanotube- and graphene-based nanomaterials and applications in high-voltage supercapacitor: A review

Carbon nanotubes are promising materials for various applications. In recent years, progress in manufacturing and functionalizing carbon nanotubes has been made to achieve the control of bulk and surface properties including the wettability, acid–base properties, adsorption, electric conductivity and capacitance. In order to gain the optimal benefit of carbon nanotubes, comprehensive understanding on manufacturing and functionalizing carbon nanotubes ought to be systematically developed. This review summarizes methodologies of manufacturing carbon nanotubes via arc discharge, laser ablation and chemical vapor deposition and functionalizing carbon nanotubes through surface oxidation and activation, doping of heteroatoms, halogenation, sulfonation, grafting, polymer coating, noncovalent functionalization and nanoparticle attachment. The characterization techniques detecting the bulk nature and surface properties as well as the effects of various functionalization approaches on modifying the surface properties for specific applications in catalysis including heterogeneous catalysis, photocatalysis, photoelectrocatalysis and electrocatalysis are highlighted.

Carbon nanotube catalysts: recent advances in synthesis, characterization and applications.

Nanocatalysts are characterised by the unique nanoscale properties that originate from their highly reduced dimensions. Extensive studies over the past few decades have demonstrated that the size and shape of a catalyst particle on the nanometre scale profoundly affect its reaction performance. In particular, controlling the catalyst particle morphology allows a selective exposure of a larger fraction of the reactive facets on which the active sites can be enriched and tuned. This desirable surface coordination of catalytically active atoms or domains substantially improves catalytic activity, selectivity, and stability. This phenomenon is called morphology-dependent nanocatalysts: catalyst particles with anisotropic morphologies on the nanometre scale greatly affect the reaction performance by selectively exposing the desired facets. In this review, we highlight important progress in morphology-dependent nanocatalysts based on the use of rod-shaped metal oxides with characteristic redox and acid-base features. The correlation between the catalytic properties and the exposed facets verifies the chemical nature of the morphology effect. Moreover, we provide an overview of the interactions between the rod-shaped oxides and the metal nanoparticles in metal-oxide catalyst systems, involving crystal-facet-selective deposition of metal particles onto different crystal facets in the oxide supports. A fundamental understanding of active sites in morphologically tuneable oxides enclosed by the desired reactive facets is expected to direct the development of highly efficient nanocatalysts.

Morphology-dependent nanocatalysts: Rod-shaped oxides

Methane decomposition to COx-free hydrogen and nano-carbon material on group 8–10 base metal catalysts: A review

Preparation and characterization of polyaniline/multi-walled carbon nanotube composites

Methane decomposition over a Ni/Cu/Al 2 O 3 catalyst is studied in a two-stage fluidized bed reactor. Low temperature is adopted in the lower stage and high temperature in the upper stage. This allows the fluidized catalysts to decompose methane with high activity in the high temperature condition; then the carbon produced will diffuse effectively to form carbon nanotubes (CNTs) in both low and high temperature regions. Thus the catalytic cycle of carbon production and carbon diffusion in micro scale can be tailored by a macroscopic method, which permits the catalyst to have high activity and high thermal stability even at 1123 K for hydrogen production for long times. Such controlled temperature condition also provides an increased thermal driving force for the nucleation of CNTs and hence favors the graphitization of CNTs, characterized by high resolution transmission electron microscopy (HRTEM), Raman spectroscopy and XRD. Multistage operation with different temperatures in a fluidized bed reactor is an effective way to meet the both requirements of hydrogen production and preparation of CNTs with relatively perfect microstructures.

Production of hydrogen and carbon nanotubes from methane decomposition in a two-stage fluidized bed reactor

Carbon nanotubes (CNTs) prepared from ethylene decomposition over the Fe/Al 2 O 3 catalyst are studied in a packed bed (PB) reactor and a nanoagglomerate fluidized bed reactor (NABR), respectively. CNTs sampled at different reaction times are characterized by TEM, Raman spectroscopy, and particle size analysis. The bulk density and agglomerate size of CNTs increase significantly with reaction time in a PB, while it remains at a stable level in NABR. Also, CNTs with good morphology, narrow diameter distribution, and fewer lattice defects are obtained in an NABR, rather than in a PB. In contrast to the unavoidable jamming due to volume increase of CNTs observed in a PB, a continuous CNT growth process is attained in an NABR, even though the amount of CNTs in an NABR is 6-7 times that in a PB. The flow dynamics, available space for growing, and mass and heat transfer can be controlled in an NABR, which favors the large-scale production of CNTs with uniform properties.

Production of carbon nanotubes in a packed bed and a fluidized bed

Effect of hydrothermal treatment on the acidity distribution of γ-Al 2 O 3 support

The research on monovinylacetylene production from dimerization of acetylene is reviewed,including the catalyst,production technology and reaction mechanism.Besides,development of the process,improvement scheme of the production techniques and development of downstream products of monovinylacetylene on the background of current energy and technique are also proposed.

Research progress of dimerization of acetylene to monovinylacetylene

The progress of developing the multistage fluidized bed technology in Tsinghua University was reviewed in the present work.First part presents the experiment on cold model fluidized bed to determine the operating regime,the relationship of height of dense phase of solids in different stages with gas velocity and the structure of downcomer.Second part described the application of reactor structure above in hydrogenation of nitrobenzene to aniline,ammoxidation of m-xylene,synthesis of methanol,vinyl chloride monomer from acetylene,and synthesis of carbon nanotube.The structure of multistage bed is adaptable to special processes,calling for the temperature shift,different gas atmosphere,high conversion of gas reactants or long catalyst life time.Finally,the industrial scale application was addressed,which broaden the application of multistage fluidized bed in heterogeneous catalytic processes.

Wang Zhanwen

Papers

Production of hydrogen and carbon nanotubes from methane decomposition in a two-stage fluidized bed reactor

Production of carbon nanotubes in a packed bed and a fluidized bed

Effect of hydrothermal treatment on the acidity distribution of γ-Al 2 O 3 support

Research progress of dimerization of acetylene to monovinylacetylene

Application of multistage fluidized bed in heterogeneous catalysis and nano-material synthesis