Showing papers by "Weizhong Qian published in 2019"

3D Hierarchical Porous Graphene-Based Energy Materials: Synthesis, Functionalization, and Application in Energy Storage and Conversion

Abstract: The rational development of effective energy materials is crucial to the sustainable growth of society. Here, 3D hierarchical porous graphene (hpG)-based materials with micro-, meso-, and macroporous features have recently attracted extensive research efforts due to unique porosities, controllable synthesis, versatile functionalization, favorable mass/electron transport, and superior performances in which corresponding electrochemical performances are strongly dependent on the nature of the building blocks and structural hierarchy of the assemblies. In this review, recent achievements in the controllable synthesis, versatile functionalization, and device application of 3D hpG-based energy materials will be summarized, including controllable and facile synthesis through chemical vapor deposition on 3D porous templates, post-assembly/treatment of graphene oxide nanosheets, and templated polymerization. In addition, graphene material functionalization through heteroatom doping, spatially confined decoration of active nanoparticles, and surface hybridization of graphene-analogous components to enhance electrochemical properties will be discussed. Furthermore, applications of 3D hpG materials in various electrochemical energy storage and conversion systems will be summarized, including lithium-ion batteries, lithium-sulfur batteries, lithium metal anodes, oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, and nitrogen reduction reaction. Overall, this review will comprehensively present the property advantages, design principles and synthesis strategies of 3D hpG-based energy materials and provide guidance in the development of various 2D graphene-analogous materials and nanomaterials for advanced electrochemical energy storage and conversion systems.

Modulation of b-axis thickness within MFI zeolite: Correlation with variation of product diffusion and coke distribution in the methanol-to hydrocarbons conversion

Abstract: The conversion of methanol-to-hydrocarbons (MTH) has been studied over a series of Zn/ZSM-5 zeolites with different thickness of b-axis, as well as similar lengths of a-axis. It has been demonstrated that the decrease of b-axis thickness from 220 nm to 2 nm leads to the remarkably longer lifetime, accompanied by the shift of selectivity toward trimethylbenzene and increased coke tolerance capacity. Methylbenzenes, as the intermediate product of the aromatic-based cycle, can diffuse out of the straight channels in the Zn/ZSM-5 nanosheet quickly, suppressing the aromatic-based cycle. The evolution of coke species, including the quantity, types, and location, as a function of the reaction time, has been systematically investigated. During the initial reaction period, the coke preferentially forms in mesopores and then is deposited mainly in micropores as the reaction proceeds. The Zn/ZSM-5 nanosheet shows a crystal face dependency on coke deposition, which mainly occurs on the (010) surface because the diffusion of product molecules is found to be only through the straight channels. But, for the conventional Zn/ZSM-5 catalyst, the diffusion of small molecule products is through both channels, while aromatics are only diffused through the straight channels, which leads to the significant difference of coke densities and sp2/sp3 ratios on the (010) and (100) surfaces. The adsorption simulations indicate that butene and p-xylene are the largest molecules which diffuse through the sinusoidal channels and the straight channels, respectively.

Highly selective conversion of methanol to propylene: design of an MFI zeolite with selective blockage of (010) surfaces

Abstract: As an important catalyst of methanol-to-propylene (MTP) conversion, the ZSM-5 zeolite has an anisotropic diffusion path and a large pore size, resulting in the formation of undesirable heavy aromatic by-products. Herein, we developed a surface-specific silica deposition method to block straight channels of nanosized ZSM-5 crystals selectively. By such a coating method, we can selectively suppress the yield of aromatics from the original 13% to 2.4% at 100% conversion of methanol. Trapped hydrocarbon pool species are directly confirmed by aberration-corrected S/TEM for the first time. Such a method of trapping and restricting hydrocarbon pool species in a multiscale zeolite with 10-membered rings would significantly increase its catalytic efficiency and olefin diffusion. Moreover, this provides new methodologies for zeolite structure construction and will be greatly beneficial for the industrial MTP process.

Perspective to the Potential Use of Graphene in Li-Ion Battery and Supercapacitor.

Abstract: Graphene is a hot star in materials science with various potential application aspects, including in Li-ion battery and supercapacitor. The burst of scientific papers in this area seems to validate the performance of graphene, but also arouses large dispute. Herein, we share our judgment of these trends to all, encouraging the discussion and enhancing the understanding of the structure-performance relationship of graphene.

Enhanced production of aromatics from propane with a temperature-shifting two-stage fluidized bed reactor

Abstract: A temperature-shifting two-stage fluidized bed reactor technology was used to convert propane and its intermediate products into aromatics. The first stage served for the aromatization of propane with a Ga/ZSM-5 catalyst at 570 °C. The second stage served for the alkylation of the intermediates of olefins at 300 °C. The increased yield of aromatics was attributed to the effective transformation of C2–C3 olefins as well as due to the suppression of the hydrogen transfer effect of the olefins.

System treating organic matter containing waste water by using adsorption method and for preparing carbon nanomaterial, and method thereof

Abstract: The invention discloses a system treating organic matter containing waste water by using an adsorption method and for preparing a carbon nanomaterial, and a method thereof. The system includes a wastewater adsorption/desorption device, a concentrated waste liquid separation device, a carbon nano material production device, a tail gas oxidation device, and a heat exchanger between the carbon nanomaterial production device and the tail gas oxidation device, or a heat exchanger between the concentrated waste liquid separation device and the carbon nano material production device. Organic mattercontaining waste water can be discharged through the waste water adsorption/desorption device when reaching the standard through the method which uses the device to convert organic matters into a carbon nanomaterial and heat to perform recycling; the organic matters obtained by concentrated waste liquid after desorption through separating can be produced into the carbon nanomaterial through the carbon nano material production device; tail gas can be produced into high temperature flue gas in the tail gas oxidation device to provide heat for other devices in the system; and therefore, the problems of hard treatment of the concentrated organic matters can be solved, and adsorbent costs can be reduced, so that the system and the method thereof can have advantages of being low in energy consumption and large in operation elasticity.

Method for preparing high-specific-surface-area macroporous-mesoporous carbon by using salt template, and applications of high-specific-surface-area macroporous-mesoporous carbon

Abstract: The invention discloses a method for preparing a high-specific-surface-area macroporous-mesoporous carbon material by using a salt template. The method comprises: dissolving biomass gelatin in hot water to form a sol, adding an inorganic salt as a templating agent, cooling to a room temperature, placing in a 4 DEG C constant-temperature box to form a hydrogel, and continuously placing at a temperature of -20 DEG C to form a frozen gel; carrying out freeze drying on the frozen gel to obtain an aerogel, and calcining at a temperature of 400-1000 DEG C under an argon atmosphere to obtain a blackcarbonized product; and carrying out water washing, suction filtration and drying to obtain the final product. According to the present invention, by using the soluble biomass carbon source and the inorganic salt as the raw materials, the method is simple, the cost is low, the poorly soluble metal template is not used, the acid washing is not required, no residual metal impurity exists, and the method is environmentally friendly; the prepared carbon material has characteristics of high specific surface area (2872 cm /g), three-dimensional continuous property, rich macropores (50-150 nm) andmesopores (2-4 nm), nitrogen atom doping and the like; and with the application of the material in 4V ionic liquid supercapacitors, the energy density of 92 Wh/kg and the excellent power density can be provided.