In the past Wei Xing has collaborated on articles with Fengzhan Si and Xiang Li. One of their most recent publications is 1 - Oxygen Solubility, Diffusion Coefficient, and Solution Viscosity. Which was published in journal .

More information about Wei Xing research including statistics on their citations can be found on their Copernicus Academic profile page.

Wei Xing's Articles: (83)

1 - Oxygen Solubility, Diffusion Coefficient, and Solution Viscosity

AbstractIn this chapter, the necessary parameters for both rotating disk electrode/rotating ring-disk electrode analysis in oxygen reduction reaction study, such as O2 solubility, O2 diffusion coefficient and the viscosity of the aqueous electrolyte solutions are discussed in depth in terms of their definitions, theoretical background, and experiment measurements. The effects of type/concentration of electrolyte, temperature, and pressure on values of these parameters are also discussed. To provide the readers with useful information, the values of these parameters are collected from literature, and summarized in several tables. In addition, the values of both the O2 solubility and diffusion coefficient in Nafion® membranes or ionomers are also listed in the tables. Hopefully, this chapter would be able to serve as a data source for the later chapters of this book, and also the readers could find it useful in their experimental data analysis.

4 - Electrochemical Oxygen Reduction Reaction

AbstractIn this chapter, the fundamentals of oxygen reduction reaction (ORR) including thermodynamics and electrode kinetics are presented. The ORR kinetics including reaction mechanisms catalyzed by different electrode materials and catalysts including Pt, Pt alloys, carbon materials, and nonnoble metal catalysts are discussed based on the literature in terms of both experiment and theoretical approaches. It is emphasized that these fundamentals of ORR are necessary in order to perform the meaningful characterization of catalytic ORR activity using both rotating disk electrode and rotating ring-disk electrode methods.


No abstract

Technical CommuniqueSome geometric properties of Lyapunov equation and LTI system☆

AbstractWhile many algebraic properties of Lyapunov equation and LTI system are well known, few geometric properties, which may be used to analyze control system properties are studied. In this paper, some new necessary and sufficient conditions based on geometry are derived for properties of the Lyapunov equation and LTI system.

Microwave polyol synthesis of Pt/CNTs catalysts: Effects of pH on particle size and electrocatalytic activity for methanol electrooxidization

AbstractPt nanoparticles with different mean sizes supported on carbon nanotubes were synthesized by microwave heating ethylene glycol solutions of platinum salt with different pH in present of CNTs as supports. TEM examinations showed that Pt particles become smaller and more uniform when the synthesis pH increased from 3.4 to 9.2. The mean particle size was 5.8, 5.2, 3.4 and 2.7 nm when the synthesis pH was 3.6, 5.8, 7.4 and 9.2, respectively. The effects of the pH on Pt particle size and distribution were investigated. The pH was an important factor that influenced the particle size. Pt particles size could be thus selected by adjusting the synthesis solution pH. Pt/CNTs with suitable and uniform Pt particle size could be obtained. Electrochemical measurements showed that the Pt/CNTs catalyst prepared from the synthesis solution pH of 7.4 exhibited better performances for methanol electrooxidization than other samples.

The construction of nitrogen-doped graphitized carbon–TiO2 composite to improve the electrocatalyst for methanol oxidation

AbstractThe exploration of advanced catalyst supports is a promising route to obtain electrocatalysts with high activity and durability. Herein, the nitrogen-doped graphitized carbon/TiO2 composite was fabricated and explored as support for the Pt catalyst. The composite support was constructed by carbonization of polypyrrole/TiO2 using cobalt nitrate and nickel nitrate as graphitizing catalysts. The resulting catalyst shows enhanced electrocatalytic performance for methanol electrooxidation compared with the commercial Pt/C catalyst. The enhancement can be ascribed to combinatory effect of N-doped graphitized carbon and TiO2, in which the tolerance to CO-poisoning and the intrinsic kinetics of methanol oxidation reaction were simultaneously improved by the bifunctional effect and the modification of the electronic structure. As a result, the as-developed nitrogen-doped graphitized carbon/TiO2 composite present attractive advantages for the application in fuel cell electrocatalyst.

Superhigh-rate capacitive performance of heteroatoms-doped double shell hollow carbon spheres

AbstractThe salient practical application feature of an ideal supercapacitor is its ability to deliver high energy density stably even at ultrahigh power density. Therefore, a rational design of electrode materials is essentially required for achieving high current, energy and power densities. In this work, a special “in situ replicating” strategy is employed to fabricate double shell hollow carbon spheres with homogeneously doped heteroatoms. The KOH activation introduces micropores to the thin shells of the hollow carbon spheres. Materials characterizations show that these carbon spheres have such merits as large surface area, easy-accessible micropore surface with faradaic reaction sites, and high conductivity. All these result in ultrafast ion transport from electrolyte to the micropores in the carbon spheres and endow the carbon with outstanding capacitive performance, e.g., an unprecedentedly high specific capacitance of 270 F g−1 at a very high current density of 90 A g−1. Moreover, a high energy density of 11.9 Wh kg−1 at a respectable power density of 30,000 W kg−1 is achieved in 6 M KOH electrolyte.

TiO2 inserted carbon materials with fine-tuned pore structure as effective model supports for electrocatalysts of fuel cells

AbstractCommercially available carbon black is a widely applied support material for nanocatalysts but notorious for its microporous structure, which is deleterious for catalysts utilization in the fuel cell application and causes numerable problems in other application areas. The development of mesoporous carbon as a substitute was proved successful but not scalable due to their intrinsic complex synthesis. In this work, we demonstrate a new perspective to circumvent the problem through blocking the micropores of carbon black by the in-situ formed TiO2 nano/sub-nano particles. A decompression absorption method was developed where tetrabutyl titanate was pressurized into carbon pores with diameter <3 nm, succeeded by hydrolysis and calcination to form the TiO2 inserted commercial carbon black, such as BP2000 and Vulcan XC-72. The TiO2–C hybrid material with reduced micropore volume was found an excellent support for noble catalysts, such as Pt and Pd nanoparticles, where their insertion into carbon micropores during synthesis were prevented, thus leading to improved metal utilization. The TiO2–C supported catalysts exhibited much superior activity and stability for methanol or formic acid electrooxidation in comparison to the plain carbon black. This work also demonstrated the negative effects of micropores in carbon support.

The anti-tumor effect of human monocyte-derived dendritic cells loaded with HSV-TK/GCV induced dying cells

AbstractHerpes simplex virus thymidine kinase (HSV-TK) gene and dendritic cells (DC) have been used as the pioneering in cancer therapy. HSV-TK gene can induce apoptosis and necrosis in tumor cells in the presence of the non-toxic prodrug ganciclovir (GCV). We investigated the anti-tumor effect of DC vaccination by introducing dying cells from HSV-TK gene treatment as an adjuvant. HepG2-TK cell line was established by transfecting human hepatoma cell line HepG2 (HLA-A2 positive) with HSV-TK gene. Dying tumor cells were generated by culturing HepG2-TK cells with GCV. After engulfed dying cells efficiently, immature DCs (imDC) derived from human monocytes were fully matured and elicited marked proliferation and cytotoxicity against HLA matched HepG2 cells in autologous peripheral blood mononuclear cells (PBMC). It also implied that HepG2 specific CTLs played an important role in the cytotoxicity which was primarily depended on Th1 responses. Given the feasibility of inducing dying cells by HSV-TK/GCV in vivo, our results suggest an effective method in clinical human hepatocellular carcinoma (HCC) treatment by an in vitro model of applying HSV-TK gene modified human tumor cells integrated with DC vaccination.

Structure–activity relationship of surfactant for preparing DMFC anodic catalyst

AbstractThree kinds of surfactants as stabilizer were applied to the preparation of electrocatalysts for direct methanol fuel cell (DMFC). The catalysts have been characterized by examining their catalytic activities, morphologies and particle sizes by means of cyclic voltammetry, chronoamperometry, X-ray diffraction and transmission electron microscopy (TEM). It is found that the surfactants with different structures have a significantly influence on the catalyst shape and activity. The catalysts prepared with non-ionic surfactants as the stabilizer show higher activity for direct oxidation of methanol. The structure–activity relationship (SAR) analysis has been explored and the effect of hydrophile–lipophile balance (HLB value) has also been discussed.

A comparative study of Pt/C and Pt–MoOx/C catalysts with various compositions for methanol electro-oxidation

AbstractThe methanol electro-oxidation behaviors on the Pt–MoOx/C catalysts with various compositions were investigated and compared to those of Pt/C catalyst by cyclic voltammetry and chronoamperometry. The Pt–MoOx/C catalysts were prepared by depositing Pt on the MoOx/C support obtained by precipitation-reduction method in advance. The physical properties of the prepared catalysts were characterized by XRD, XPS, EDX and TEM. From the results of XRD and TEM, it was shown that the MoOx/C support facilitated the dispersion of Pt particles. All the Pt–MoOx/C catalysts showed relative lower Mo contents comparing to their nominal values. No PtMo alloy was formed in these catalysts, which were affirmed by XPS and XRD. It was found that all the Pt–MoOx/C catalysts showed higher mass activity (normalized to the mass of Pt) but lower specific activity (normalized to the electrochemical active surface areas) for methanol oxidation than the Pt/C catalyst. With the increase of Mo contents in Pt–MoOx/C catalysts, the activities of Pt–MoOx/C catalysts decreased. Combined with the composition and structure analyses, the differences in methanol oxidation on these catalysts were attributed to the interaction between the Pt particles and the MoOx/C support. It was suggested that the Pt metal–MoOx/C support interaction resulted in two effects. One was decreasing the Pt particle size; the other was decreasing the specific activities of these catalysts for methanol oxidation. Comprising these two contradictory effects, the mass activities of these catalysts for methanol oxidation increased.

Pt/C anodic catalysts with controlled morphology for direct dimethyl ether fuel cell: The role of consecutive surface

AbstractTwo types of Pt nanowires (NWs)/C catalysts with different aspect ratios and one type of Pt nanoparticles/C catalyst are successfully synthesized, and DME electrochemical performance on different extent consecutive surfaces is investigated. The morphology and crystallization are confirmed with electron microscopes and XRD. The electrochemical tests show that the nanowire catalysts, especially the one with higher aspect ratio, possess higher electrochemical surface areas, higher absorption capacity of DME, higher CO tolerance, higher electron transfer coefficient, and higher activity towards DME electrooxidation than those of the nanoparticle catalyst. The results prove that the consecutive surface favors for direct dimethyl ether fuel cell (DDFC) anodic catalyst, which are contributive to the study of the mechanism of DME electrooxidation on Pt surface and designing an effective catalyst for anodic DDFC.

Improved direct electrooxidation of formic acid by increasing Au fraction on the surface of PtAu alloy catalyst with heat treatment

AbstractThe PtAu/C alloy catalyst is firstly synthesized by the co-reduction of both metal precursors under microwave conditions and then heat-treated to enable the migration of Au atoms to the exterior surface of the obtained PtAu/C catalyst. The bulk crystallite structures and the surface Au contents of PtAu/C catalysts are characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The electrocatalytic activity and durability measurements exhibit the superior catalytic performance of PtAu/C catalysts over that of Pt/C catalyst on formic acid electrooxidation. Moreover, the initial and final activity after 3600 s reaction of the heat-treated PtAu/C alloy catalyst is two and five times as high as that of the untreated PtAu/C catalyst. The performance enhancement of the PtAu/C catalysts is discussed in terms of the electronic effect and ensemble effect.

Effect of cation nature of zeolite on carbon replicas and their electrochemical capacitance

AbstractN-doped carbon replicas of zeolite Y are prepared, and the effect of cation nature of zeolite (H+ or Na+) on the carbon replicas is studied. The morphology, structure and surface properties of the carbon materials are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The pore regularity, pore parameter and surface chemical properties of the carbons may strongly depend on the cation nature of the zeolite Y. The carbon replicas of zeolite HY (H-form of zeolite Y) possesses higher pore regularity and much larger surface area than those of zeolite NaY (Na-form of zeolite Y), while the latter carbons seem to possess higher carbonization degrees. Electrochemical measurements show a large faradaic capacitance related to the N- or O-containing groups for the prepared carbons. Owing to the large specific surface area, high pore regularity and heteroatom-doping, the HYC800 sample derived from zeolite HY presents very high gravimetric capacitance, up to 312.4 F g−1 in H2SO4 electrolyte, and this carbon can operate at 1.2 V with good retention ratio in the range of 0.25 to 10 A g−1.

Nitrogen-doped graphene as low-cost counter electrode for high-efficiency dye-sensitized solar cells

AbstractNitrogen-doped graphene (NDG) sheets are prepared by a hydrothermal reduction of graphite oxide using ammonia as the nitrogen source and employed as the catalyst for triiodide reduction to fabricate counter electrodes in dye-sensitized solar cells. It is found that chemical reduction and nitrogen doping of graphite oxide are achieved simultaneously via a simple hydrothermal process. Electrochemical impedance spectroscopy analysis reveals that the charge-transfer resistance of NDG electrode decreases with increasing the NDG loading. The electrode with a NDG loading of 20 μg cm2 shows a charge-transfer resistance of 0.9 Ω cm2, which is much lower than that of pristine graphene electrode. Such electrocatalytic activity enhancement is mainly attributed to the structural defects and edge plane exposure in NDG. This enhanced electrochemical property is beneficial for improving the photovoltaic performance of dye-sensitized solar cells. Under 1 sun illumination (AM 1.5), the dye-sensitized solar cell with NDG electrode shows an energy conversion efficiency of 7.01%, which is comparable to that of the cell with Pt electrode.

Reconstructed PtFe Alloy Nanoparticles with Bulk-Surface Differential Structure for Methanol Oxidation

AbstractThe high cost of the catalyst material is a large obstacle for the commercialization of Direct Methanol Fuel Cells. In present work, the non-noble metal Fe was added to the conventional Pt/C catalyst in order to lowering the catalyst cost without sacrificing the catalytic performance. A chemically dealloying procedure was adopted to leach out the surface iron atoms and thereby increasing the stability of the catalyst. Through these procedures, the PtFe bulk-surface differential nano-catalyst was obtained. The shift in diffraction angles according to XRD spectra confirms the formation of the alloy structure between Pt and Fe. TEM results indicate that the chemically dealloyed PtFe/C nanoparticles are uniformly-dispersed with optimized average size. The PtFe bulk-surface differential structure is inferred from XPS as no surface Fe atoms are detected in spite of the change in Pt electronic structure. The existence of Fe atoms inside the nanoparticles is further confirmed by the ICP characterization. Electrochemical characterizations show that the catalytic activity is increased to 2.8 times, compared to the Pt/C catalyst, which can be ascribed to the electronic effect of Fe. A further evidence for the electronic effect comes from the CO stripping spectroscopy, in which the onset potential for CO oxidation shifts dramatically toward the negative potential side compared with Pt/C. Owing to the bulk-surface differential structure, the chemically dealloyed PtFe/C catalysts exhibits nearly the same stability compared to that of the Pt/C catalyst.

Studies in the capacitance properties of diaminoalkane-intercalated graphene

AbstractA series of diaminoalkane-intercalated graphenes (DIGs) are successfully synthesized by intercalating graphite oxide with diaminoalkanes, followed by a reduction process using hydrazine as a reductant at room temperature. The as-prepared intercalated graphite oxides (DIGOs) and their reduced products are characterized using a variety of approaches such as X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and elemental analysis. Electrochemical tests show that the specific capacitances of DIGOs and DIGs decrease with the increase of the interlayer distance, and that the DIGs possess larger capacitance than DIGOs after hydrazine reduction. The ion diffusion in the DIGOs/DIGs follows pseudo-second-order kinetics and is dominated mainly by their pore sizes.

Nitrogen-doped hierarchical porous carbon materials prepared from meta-aminophenol formaldehyde resin for supercapacitor with high rate performance

Highlights•A mass produced nano-SiO2 is used to prepared hierarchical porous carbon.•N-doped hierarchical porous carbon materials are easily prepared.•The NHPCs materials exhibit a very high capacitance of up to 260.5 F g−1.•The NHPC-800 sample shows very high rate capability.•Hierarchical porosity and N-doping synergistically enhances the whole capacitance.

Surfactant assisted electrospinning of WS2 nanofibers and its promising performance as anode material of sodium-ion batteries

AbstractMetal sulfides were considered as a promising anode material for sodium-ion batteries (SIBs). However, volume expansion during charging/discharging is an issue. One dimensional nanofibers are considered here to alleviate the change in stress of the anode's structure. Here we incorporated the nanofibers and WS2 nanosheets which used (DODA)3PW12O40 as the precursor. The precursor was prepared by an ion-exchange method, and then used to fabricate the anode material (denoted as DODA-WS2) via electrospinning. Use of surfactant dimethyldistearylammonium bromide (DODA·Br) disperses the WS2 nanosheets in the nanofibers. Carbonization and decomposition of DODA ligands provides porosity that accommodates volume expansion. The resulting structure of the anode material delivers high capacities of 363 and 318 mAh g−1 with 96% and 91% rate capacity retention after 400 cycles at 200 and 500 mA g−1, respectively. Also, improved rate capabilities (395 and 91 mAh g−1 at 50 and 10000 mA g−1, respectively) and good cycling stability (226.5 mAh g−1 after 800 cycles at 1000 mA g−1). These unique results are ascribed to the well-dispersed WS2 cross-linked nanofiber framework and its conductive network. This structure facilitates the transportation of electrons and Na+ and relieve the stress due to expansion. DODA-WS2 has a high potential for use as anode materials in SIBs.

Immunopharmacology and inflammationThe anti-inflammatory effects of sanguinarine and its modulation of inflammatory mediators from peritoneal macrophages

AbstractThe quaternary ammonium salt, sanguinarine (SANG), is of great practical and research interest because of its pronounced, widespread physiological effects, which promote anti-microbial and anti-inflammatory responses in experimental animals. Sanguinarine was originally shown to possess anti-inflammatory properties and it has been used to treat various inflammatory diseases. To gain insight into the anti-inflammatory effect of sanguinarine and its mechanisms of action, we used animal models of acute and chronic inflammation and lipopolysaccharide (LPS)-induced murine peritoneal macrophages to examine the anti-inflammatory function of sanguinarine. Sanguinarine displayed significant anti-inflammatory effects both in vitro and in vivo. Our findings further demonstrated that sanguinarine potently inhibited the expression of inflammatory mediators and inflammation in general. Additionally, our results demonstrated that sanguinarine inhibited the activation of mitogen-activated protein kinase (MAPK), which altered inflammatory mediator synthesis and release in vitro. This study extends our understanding of the anti-inflammatory activity of sanguinarine in acute and chronic inflammation. Furthermore, our findings provide clarification of the molecular mechanisms underlying the anti-inflammatory activity of sanguinarine, supporting the naturopathic use of sanguinarine for the treatment of various human inflammatory diseases.

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