Preparation of PtNi/C electrocatalysts for direct methanol fuel cell via pulse microwave assisted polyol method

PtNi/C nanoparticles with different atomic ratios of Pt/Ni were produced in pulse microwave assisted polyol process. Transmission electron microscopy（TEM） images show uniform morphology. X-ray diffraction（XRD） pattern plus energy dispersive X-ray（EDX） spectroscopy suggests pure composition. Cyclic voltammogram study reveals that PtNi/C nanoparticles synthesized in pulse microwave assisted polyol process have better catalytic activity for the oxidation of methanol to carbon dioxide than those synthesized in continuous process.     

Peanut-Like Hematite Prepared by a New Facile Hydrothermal Process for Removal of As(V)

Peanut-like hematite has been prepared by a new facile hydrothermal method and applied in the adsorption removal of As(V). The structural features of the as-prepared hematite were characterized systematically by X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, scanning electron microscopy, energy-dispersive X-ray spectroscopy mapping, Fourier transform infrared spectroscopy, and transmission electron microscopy. Results showed that the morphologies of hematite could be tuned to spindle-like, oval-like, and cantaloupe-like shapes by adjusting the hydrothermal conditions. The peanut-like hematite formation followed a five-step route. At pH = 3, the adsorption amount of As(V) over peanut-like hematite reached 13.84 mg/g, and the adsorption kinetic process corresponded to the pseudo-second-order kinetic model. The peanut-like hematite also showed partial selectivity over As(V) in the hydrosphere. This method can be a reference for the preparation of other architectural metal oxide materials.     

Oxidation Characteristics of the Reactivity Between Pyrite and Aqueous Arsenate

Natural pyrites contain high levels of adsorbed and structurally incorporated arsenic(As),which may simultaneously result in the release of As and affect the oxidation process of pyrite.However,the oxidation and electrochemical behaviors of As on the oxidation reactivity of pyrites are still not clear.In this study,pyrite was prepared by a hydrothermal method and applied to study the oxidation mechanism between pyrite and aqueous arsenate.Analyses of X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy demonstrate that the as-prepared sample is an octahedron-like pyrite with high purity and crystallinity.The interaction between As(V)and pyrite as well as the electrochemical behaviors of pyrite oxidation in the presence of aqueous arsenate were investigated under acidic conditions by an ion analysis method,cyclic voltammetry(CV),Tafel,and electrochemical impedance spectroscopy(EIS).The results of the chemical reaction indicate that electrons are transferred from S _2~(2-)to dissolved oxygen with the formation of SO _4~(2-)in the initial As(V)concentration range of 0–0.3 mmol/L.In the initial As(V)concentration range of 0.4–1.2 mmol/L,electrons are transferred from S _2~(2-)to As(V)with the formation of elemental S ~(0 )and As(III).The CV,the Tafel plot and EIS analyses indicate that aqueous arsenate in an electrolyte promotes oxidation reactivity and passivation of the pyrite electrode.Moreover,the electron transfer rate increases with increasing aqueous arsenate concentration in the electrolyte.     

Gold Nanoparticles of Multiple Shapes Synthesized in L-Tryptophan Aqueous Solution

In this paper, we describe a simple and efficient synthesis of gold nanoparticles(GNPs) of various shapes(spherical, rod-like, hexagonal, truncated triangular, and triangular) using Au(Ⅲ) reduction in aqueous solutions by L-tryptophan. We evaluated the influences of reaction temperature, foreign metal ions Ag(Ⅰ), and surfactants of nonionic(polyethylene glycol, PEG), anionic(sodium dodecyl sulfate, SDS), and cationic(cetyltrimethyl ammonium bromide, CTAB) on GNPs synthesis. We characterized the resultant GNPs using UV–visible adsorption spectroscopy, transmission electron microscopy/high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, selected-area electron diffraction, and Fourier-transform infrared spectroscopy. We fabricated the variously sized GNPs by controlling the rate of the reduction of gold ions in aqueous solution by varying the reaction temperature: the higher the temperature, the smaller the gold nanospheres. We found the existence of Ag(Ⅰ) to reinforce the reduction of Au(Ⅲ) and to correspond with the appearance of some amorphous bimetallic Au/Ag nanoparticles. Additionally, we found the presence of surfactants to greatly influence the shape of the formed GNPs, especially the presence of CTAB, which results in the anisotropic growth of gold nanocrystals into hexagonal, truncated triangular, and triangular nanoplates. In addition, with the increase in CTAB concentration, we found the amount of gold nanoplates to first increase and then decrease. Finally, we performed preliminary explorations of the reduction process and morphological evolution to propose possible corresponding reduction and morphological evolution pathways.     

Catalytic oxidation degradation of phenol in wastewater by heterogeneous Fenton reagent

Heterogeneous Fenton reagent, as a strong oxidizer, has been used widely in the treatment of wastewater. We prepared Fe2O3/γ-Al2O3 catalyst by impregnation method and characterized it by powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). Test results show that Fe2O3 crystal was compounded on the γ-Al2O3 carrier. We tested and optimized Fe2O3/γ-Al2O3/H2O2 and Fe2O3/γ-Al2O3/H2O2 /UV processes to remediate organic material of phenol, using phenol solution with an initial concentration of 250 mg/L as a representative of phenolic industrial wastewater. The preparation conditions were optimized based on performance of Fe2O3/γ-Al2O3 catalyst and the processes to degrade phenol in aqueous environments. The experimental results showed that the phenol removal perfomance with Fe2O3/γ-Al2O3/H2O2 /UV was more complete than with Fe2O3/γ-Al2O3/H2O2 and degradation rate of phenol reached 89.4and 94.7respectively after reaction for 2 h.     

Synthesis and Characterization of Co-Doped Brookite Titania Photocatalysts with High Photocatalytic Activity

Transition metal-doping could effectively extend the light response range of TiO _2 photocatalysts from the ultraviolet(UV)to the visible region.Co-doped brookite titanium dioxide(Co–TiO_2)photocatalysts were synthesized via the hydrothermal method with titanium tetrachloride as the raw material and cobalt chloride hexahydrate as the dopant.The prepared Co–TiO_2 photocatalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and UV–Vis diffuse reflectance spectroscopy(UV–Vis DRS).The photocatalytic activities of Co–TiO _2 photocatalysts were evaluated by photocatalytic degradation of isopropanol alcohol(IPA),a typical volatile organic compound(VOC),under visible light.The influences ofdifferent Co doping rates,initial concentrations of IPA gas and the amounts of photocatalyst addition were also studied.At the same time,the enhancement mechanism ofcobalt ions as a trap for photogenerated holes was discussed.Thus,we found the optimum doping rate,initial concentration of IPA gas and amount of photocatalyst to add.The results show that the mesoporous Co–TiO _2 photocatalysts possess smaller size particles,larger specific surface area,lower forbidden bandgap energy(Eg)and better photocatalytic activity than pure brookite TiO _2.When the doping of Co was 7% by mass,the initial concentration ofIPA gas was 1.0×10~(-6 )mol/L and the addition of Co–TiO_2 photocatalysts was 50 mg,the best photocatalytic activity was achieved.Furthermore,the degradation rate ofIPA was up to 91%,which shows great potential for waste water treatment.     

A Novel Method for Synthesizing p-Benzoquinone by Direct Catalytic Oxidation of Benzene with Hydrogen Peroxide over Copper-Doped TS-1

Existing methods for synthesizing p-benzoquinone have drawbacks with respect to environmental protection, production scale, or industrial value. Therefore, it is imperative that a simple and environmentally friendly alternative be developed. The approach that involves preparing p-benzoquinone by the catalytic oxidation of benzene with hydrogen peroxide(H_2O_2) over copper-modified titanium silicalite-1(Cu/TS-1) has a certain superiority due to its green synthesis and mild reaction conditions. In this study, Cu/TS-1 catalyst was prepared by the wet impregnation of TS-1 with an aqueous solution of Cu(NO_3)_2 and then characterized by X-ray diffraction, Fourier transform infrared spectroscopy, diffuse reflectance UV–Vis spectroscopy, scanning electron microscopy, inductively coupled plasma mass spectrometry, X-ray fluorescence, and analysis of the N_2 adsorption–desorption isotherms. The results reveal that Cu species exist mainly in the form of amorphous Cu O that is well dispersed on the surface of catalysts, with no major change in the molecular sieve framework. After optimizing the reaction conditions, a desirable p-benzoquinone selectivity(88.4%) and benzene conversion(18.3%) were obtained when the doping of Cu in Cu/TS-1 is 1.95 wt%. In addition, Cu/TS-1 can be conveniently regenerated, showing a slight decrease in catalytic capability after initial use, which then stabilizes in subsequent circulations. The satisfactory stability and low cost of synthesizing Cu/TS-1 give this method considerable potential for further industrialization.     

Fast evaluation of degradation degree of organic coatings by analyzing electrochemical impedance spectroscopy data

The degradation coefficient is proposed to evaluate the degradation degree of organic coatings by directly analyzing the Bode plots of the electrochemical impedance spectroscopy (EIS) data.This paper investigated the degradation of phenolic epoxy coating/tinplate system by EIS and the degradation coefficient value,which correlates well with the results of breakpoint frequency and variation of phase angle at 10 Hz.Furthermore,the degradation process was confirmed by scanning electron microscope (SEM) and scanning probe microscopy (SPM).It is concluded that degradation coefficient can be used for the fast evaluation of degradation degree of organic coatings in practical applications.     

Quasi-Spherical Brookite TiO_2 Nanostructures Synthesized Using Solvothermal Method in the Presence of Oxalic Acid

Brookite TiO_2,the latest TiO_2 photocatalyst,promises to be an interesting candidate for photocatalytic applications because of its unique physical and chemical properties. In this study,pure-phase brookite TiO_2 with a quasi-spherical nanostructure was successfully synthesized via a solvothermal method using tetrabutyl titanate(Ti(OC_4H_9)_4,TBOT) as the Ti source in the presence of oxalic acid. NaOH was used to regulate the pH of solution. The structure and morphology of the samples were then analyzed using multiple methods,such as X-ray diff raction(XRD),Raman spectroscopy,scanning electron microscopy(SEM),transmission electron microscopy(TEM),Brunauer–Emmett–Teller(BET) measurements and ultraviolet–visible diff use spectroscopy(UV–Vis). Photocatalytic activities of the as-synthesized brookite TiO_2 were evaluated by degrading aqueous methylene blue solution under UV light irradiation. The effect of thermal treatment temperature on photocatalytic activity of the samples was also investigated. The produced brookite TiO_2 nanopowders calcined at 500 °C for 2 h showed the highest photocatalytic activity,and the corresponding degradation rate of methylene blue(10 mg/L) reached 96.7% after 90 min of illumination. In addition,the formation mechanism of pure-phase brookite TiO_2 was investigated. It was found that the formation of pure-phase brookite TiO_2 in this study was ascribed to the combined action of oxalic acid and sodium hydroxide.     

Synthesis and Optimization of TiO_2/Graphene with Exposed {001} Facets Based on Response Surface Methodology and Evaluation of Enhanced Photocatalytic Activity

Response surface methodology(RSM) was employed to optimize the control parameters of TiO_2/graphene with exposed {001} facets during synthesis, and its enhanced photocatalytic activities were evaluated in the photodegradation of toluene. Experimental results were in good agreement with the predicted results obtained using RSM with a correlation coefficient(R~2) of 0.9345. When 22.06 mg of graphite oxide(GO) and 2.09 mL of hydrofluoric acid(HF) were added and a hydrothermal time of 28 h was used, a maximum efficiency in the degradation of toluene was achieved. X-ray diffraction(XRD), transmission electron microscopy(TEM), and scanning electron microscopy(SEM) were employed to characterize the obtained hybrid photocatalyst. The electron transferred between Ti and C retarded the combination of electron–hole pairs and hastened the transferring of electrons, which enhanced the photocatalytic activity.     

Effects of doping Fe and Al on microstructure and electrochemical characteristics of Mg-based hydrogen storage alloys

The Mg-based hydrogen storage alloys Mg2Ni, Mg2Ni0.7Fe0.3 and Mgl.7Alo.3Ni were successfully synthesized by a two-step process （sintering and ball milling）. The crystal structure and microstructure were examined by X-ray diffraction, Scanning Electron Microscope and Malvern particle size analyzer. New phase appears in the tripe alloys doped with A1 and Fe, and the particle size ranges from 3μm to 5 μm. The electrochemical performance studies indicate that the partial substitution of AI for Mg, and Fe for Ni significantly improve the cycle life, reversibility of hydrogen absorption and desorption. The diffusion process is the control step in the electrode reaction of hydrogen storage alloys.     

Science Letters： Structure relationship of nitrochlorobenzene catalytic degradation process in water over palladium-iron bimetallic catalyst

Two isomers ofnitrochlorobenzene （o- andp-NCB） were treated by a Pd/Fe catalyst in aqueous solutions through catalytic amination and dechlorination. Nitrochlorobenzenes are rapidly converted to form chloroanilines （CAN） first through an amination process, and then rapidly dechlorinated to become aniline （AN） and CI^-, without the involvement of any other intermediate reaction products. The amination and dechlorination reaction are believed to take place predominantly on the surface site of the Pd/Fe catalysts. The dechlorination rate of the reductive degradation of the two isomers of nitrochlorobenzene （o-, and p-NCB） in the presence of Pd/Fe as a catalyst was measured experimentally. In all cases, the reaction rate constants were found to increase with the decrease in the Gibbs free energy （correlation with the activation energy） of NCBs formation; the activation energy of each dechlorination reaction was measured to be 95.83 and 77.05 kJ/mol, respectively for o- and p-NCB. The results demonstrated that p-NCBs were reduced more easily than o-NCBs.     

Characterization of Passive Film Formed on 304 SS in Simulated Alkaline Water Chemistries Containing Sulfur at 300℃

Passivity degradation of 304 stainless steel(SS) in simulated alkaline water chemistries at 300℃ was investigated using polarization curve, scanning electron microscope, time-of-flight secondary ion mass spectrometry(SIMS) and X-ray photoelectron spectroscopy(XPS). Experimental results indicated that 304,SS was selfpassive in the test solution and the thickness of passive film was about 500 nm. Hydroxide was enriched in the outer layer whereas oxide was enriched in the inner layer. Sulfur in thiosulfate could be reduced into lower valence of sulfur and enter the passive film so that the composition of passive film was modified by sulfur. Fe and Cr were enriched in the passive film whereas Ni was depleted in the passive film.     

Hydrogenation of Alkylanthraquinone Over Pore-Expanded and Channel-Shortened Pd/SBA-15

SBA-15 silica was synthesized by adding normal paraffin and alkyl benzene as swelling agents and using a low-temperature gelation procedure.Pd was then impregnated on SBA-15,yielding a catalyst.Characterizations of the catalyst by X-ray diffraction,N_2 adsorption/desorption,scanning electron microscopy,transmission electron micrographs,X-ray photoelectron spectroscopy,in situ FTIR,and a hydrogenation test of 2-ethyl-anthraquinone reveal that the addition of C_6-C_9 normal paraffin and 1,3,5-triisopropylbenzene could enlarge the pore diameter without a significant loss of ordered structure.Moreover,the length of SBA-15 pore channels decreased significantly.However,the sizes of Pd particles increase as the pore diameter is enlarged.The largest pore size (13.6 nm) and short length of pore channels (ca.0.35μm) are achieved by adding n-hexane.As a result,this catalyst exhibits the highest hydrogenation activity with an approximately 100%improvement,compared with a conventionally synthesized catalyst in the absence of a swelling agent.     

Modeling of Computational Fluid Dynamics and Experimental Study of Electro-Catalytic Oxidation Enhanced Nanofiltration for Treating C.I. Acid Red 73 Wastewater

C.I. Acid Red 73(AR73)wastewater was treated by cross-flow nanofiltration coupling electro-catalytic oxidation using an NF90 membrane and a Ti/SnO_2–Sb anode prepared via electrodeposition.Experiments conducted for standard electrochemical degradation of AR73 studied the reaction rate ofremoving AR73 using the Ti/SnO _2–Sb anode.A computational fluid dynamics(CFD)model was developed to predict the permeate flux under a laminar flow regime,including the effects ofoperating pressure,applied potential,initial concentration,and cross-flow velocity on this coupling process.The variations of the membrane surface concentration and permeate flux along the length of the channel were quantified.The experimental results were compared with those predicted by the model,and they agreed well.     

A Low-Cost and Easily Prepared Manganese Carbonate as an Efficient Catalyst for Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran

A low-cost and easily prepared manganese carbonate(Mn CO_3) has been synthesized for catalytic conversion of 5-hydroxymethylfurfural(5-HMF) to 2,5-diformylfuran(DFF). The properties and morphology of the manganese carbonate were measured by SEM,XRD,TGA,BET and XPS. In this method,no harsh reaction conditions were required,and it was a simple and green process for the oxidation of 5-HMF into DFF. To achieve an optimum DFF yield,different reaction conditions,including reaction temperature,reaction time,catalyst amount,and solvents were investigated. Results from the experiments indicated that the highest DFF yield of 86.9% was obtained at 120 °C under atmospheric oxygen pressure after 6h. Finally,Mn CO_3 could be used at least five times with considerable stability.     

Microstructure of ferrospheres in fly ashes: SEM, EDX and ESEM analysis

Ferrospheres in fly ashes from a coal-fired power plant were extracted by a magnetic separation technique and their microstructure was studied by scanning electron microscopy （SEM）, energy dispersive X-ray analysis （EDX） and environmental scanning electron microscopy （ESEM）. Ferrospheres in fly ashes show significant iron enrichment compared to their respective fly ashes. Iron oxides in ferrospheres mainly occur as minerals magnetite （Fe3O4） and hematite （α-Fe2O3）, which are derived mainly from the decomposition and oxidation of iron-bearing minerals in coal during combustion. EDX data indicate that ferrospheres also contain Si, S, Al and Ca resulting from quartz, mullite, anhydrite and amorphous materials. A large percentage of ferrospheres are commonly 5-50 μm in size. The microstructure of ferrospheres includes smooth, polygonal, dendritic, granular and molten drop characteristics. SEM coupled with EDX provided fast and accurate results of the microstructure and chemical composition of ferrospheres, and helped us to assess environmental issues related to the disposal and utilization of fly ashes.     

Elemental mercury removal from coal gas by CeMnTi sorbents and their regeneration performance

Ce and Mn modified TiO_2 sorbents(CeMnTi) were prepared by a co-precipitation method,and their ability to remove elemental mercury from coal gas in a fixed bed reactor was studied.Based on results of Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),scanning electron microscope(SEM),and X-ray photoelectron spectroscopy(XPS) studies,the modification mechanisms of the CeMnTi sorbents are discussed.Mn doping improved the specific surface area and dispersion of cerium oxides on the sorbent surface,while Ce doping increased the proportion of Mn4+in manganese oxides by a synergetic effect between manganese oxides and cerium oxides.The effects of the active component,temperature,and coal gas components on the mercury removal performance of the sorbents were investigated.The results showed that the CeMnTi sorbents exhibited high mercury removal efficiency.Ce_(0.2)Mn_(0.1)Ti adsorbed 91.55% elemental mercury from coal gas at 160℃.H_2 S and O_2 significantly improved the ability of sorbents to remove mercury.Part of the H_2S formed stable sulfates or sulfites through a series of oxidation reaction chains on the sorbent surface.HCl also improved the mercury removal performance,but reduced the promotion effect of H_2S for mercury removal when coexisting with H_2S.CO and H_2 had a minor inhibitory effect on mercury adsorption.The recycling performance of the sorbents was investigated by thermal regeneration.The thermal decomposition of the used sorbents indicated that mercury compounds were present mainly in the form of HgO and HgS,and higher temperature was beneficial for regeneration.The formation of sulfates and sulfites in the presence of H_2S led to a decrease in mercury removal efficiency.     

Optimization of Co-precipitation Condition for Preparing Molybdenum-Based Sulfur-Resistant Methanation Catalysts

In this study, the effects of ZrO_2 carrier precursors, MoO_3 loading, and washing treatment on the catalytic performance of Mo O_3/ZrO_2 toward sulfur-resistant methanation were investigated. All the catalysts were prepared by co-precipitation method and further characterized by N_2 adsorption–desorption, H_2-temperature-programmed reduction, X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The prepared MoO_3/ZrO_2 catalysts were tested in a continuous-flow pressurized fixed bed reactor for CO methanation. The results revealed that the carrier precursors, MoO_3 loading, and washing treatment affected not only the crystalline phase of Mo species but also the grain size of ZrO_2 carrier and consequently influenced the MoO_3/ZrO_2 activity toward sulfur-resistant methanation. The 25 wt% MoO_3/ZrO_2 catalyst prepared using Zr(NO_3) 4 ·5 H_2O as the precursor and treated by water washing displayed the best activity for sulfur-resistant methanation due to its greater number of octahedral Mo species and smaller ZrO_2 grain size.     

In Situ Growth of 3D Hierarchical ZnO@Ni_xCo_(1-x)(OH)_y Core/Shell Nanowire/Nanosheet Arrays on Ni Foam for High-Performance Aqueous Hybrid Supercapacitors

In this study, we designed and synthesized a novel battery-type electrode featuring three-dimensional(3D) hierarchical ZnO@Ni_xCo_(1-x)(OH)_y core/shell nanowire/nanosheet arrays arranged on Nifoam substrate via a two-step protocol including a wet chemical process followed by electro-deposition. We then characterized its composition, structure and surface morphology by X-ray diff raction, energy-dispersive X-ray spectrometry(EDS), X-ray photoelectron spectroscopy, scanning electron microscopy(SEM), transmission electron microscopy, EDS elemental mapping. Our electrochemical measurements show that the ZnO@Ni_(0.67)Co_(0.33)(OH)_y electrode material exhibited a noticeably high specific capacity of as much as 255(mA ·h)/g at 1 A/g. Additionally, it demonstrated a superior rate capability, as well as an excellent cycling stability with 81.6% capacity retention over 2000 cycles at 5 A/g. This sample delivered a high energy density of 64 W·h/kg and a power density of 250 W/kg at a current density of 1 A/g. With such remarkable electrochemical properties, we expect the 3D hierarchical hybrid electrode material presented in this work to have promising applications for the next generation of energy storage systems.