Designing ultrastable P2/O3-type layered oxides for sodium ion batteries by regulating Na distribution and oxygen redox chemistry

P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phases remains a necessity.Herein,we design a P2/O3-type Na_(0.76)Ni_(0.31)Zn_(0.07)Mn_(0.50)Ti_(0.12)0_(2)(NNZMT)with high chemical/electrochemical stability by enhancing the coupling between the two phases.For the first time,a unique Na*extraction is observed from a Na-rich O3 phase by a Na-poor P2 phase and systematically investigated.This process is facilitated by Zn^(2+)/Ti^(4+)dual doping and calcination condition regulation,allowing a higher Na*content in the P2 phase with larger Na^(+)transport channels and enhancing Na transport kinetics.Because of reduced Na^(+)in the O3 phase,which increases the difficulty of H^(+)/Na^(+) exchange,the hydrostability of the O3 phase in NNZMT is considerably improved.Furthermore,Zn^(2+)/Ti^(4+)presence in NNZMT synergistically regulates oxygen redox chemistry,which effectively suppresses O_(2)/CO_(2) gas release and electrolyte decomposition,and completely inhibits phase transitions above 4.0 V.As a result,NNZMT achieves a high discharge capacity of 144.8 mA h g^(-1) with a median voltage of 3.42 V at 20 mA g^(-1) and exhibits excellent cycling performance with a capacity retention of 77.3% for 1000 cycles at 2000 mA g^(-1).This study provides an effective strategy and new insights into the design of high-performance layered-oxide cathode materials with enhanced structure/interface stability forSIBs.

S-scheme Sb2WO6/g-C3N4 photocatalysts with enhanced visible-light-induced photocatalytic NO oxidation performance

Normal photocatalysts cannot effectively remove low-concentration NO because of the high recombination rate of the photogenerated carriers.To overcome this problem,S-scheme composites have been developed to fabricate photocatalysts.Herein,a novel S-scheme Sb2WO6/g-C3N4 nanocomposite was fabricated by an ultrasound-assisted method,which exhibited excellent performance for photocatalytic ppb-level NO removal.Compared with the pure constituents of the nanocomposite,the as-prepared 15%-Sb2WO6/g-C3N4 photocatalyst could remove more than 68%continuous-flowing NO(initial concentration:400 ppb)under visible-light irradiation in 30 min.The findings of the trapping experiments confirmed that•O2^–and h+were the important active species in the NO oxidation reaction.Meanwhile,the transient photocurrent response and PL spectroscopy analyses proved that the unique S-scheme structure of the samples could enhance the charge separation efficiency.In situ DRIFTS revealed that the photocatalytic reaction pathway of NO removal over the Sb2WO6/g-C3N4 nanocomposite occurred via an oxygen-induced route.The present work proposes a new concept for fabricating efficient photocatalysts for photocatalytic ppb-level NO oxidation and provides deeper insights into the mechanism of photocatalytic NO oxidation.

Leaching kinetics of low grade zinc oxide ore in NH_3-NH_4Cl-H_2O system

The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NH4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69 μm, holding at 80 ℃ for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2-1, and the ratio (g/mL) of solid to liquid being 1-10.

Insight into catalytic properties of Co3O4-CeO2 binary oxides for propane total oxidation

A series of Co3O4-CeO2 binary oxides with various Co/(Ce+Co)molar ratios were synthesized using a citric acid method,and their catalytic properties toward the total oxidation of propane were examined.The activities of the catalysts decrease in the order CoCeOx-70>CoCeOx-90>Co3O4>CoCeOx-50>CoCeOx-20>CeO2.CoCeOx-70(Co/(Ce+Co)=70% molar ratio)exhibits the highest catalytic activity toward the total oxidation of propane,of which the T90 is 310℃(GHSV=120000 mL h^-1 g^-1],which is 25℃ lower than that of pure Co3 O4.The enhancement of the catalytic performance of CoCeOx-70 is attributed to the strong interaction between CeO2 and Co3O4,the improvement of the low-temperature reducibility,and the increase in the number of active oxygen species.In-situ DRIFTS and reaction kinetics measurement reveal that Ce addition does not change the reaction mechanism,but promotes the adsorption and activation of propane on the catalyst surface.The addition of water vapor and CO2 in reactant gas has a negative effect on the propane conversion,and the catalyst is more sensitive to water vapor than to CO2.In addition,CoCeOx-70 exhibits excellent stability and reusability in water vapor and CO2 atmosphere.

CeO_2-ZrO_2-La_2O_3-Al_2O_3 composite oxide and its supported palladium catalyst for the treatment of exhaust of natural gas engined vehicles

Composite supports CeO2-ZrO2-Al2O3（CZA） and CeO2-ZrO2-Al2O3-La2O3（CZALa） were prepared by co-precipitation method. Palladium catalysts were prepared by impregnation and their purification ability for CH4, CO and NOx in the mixture gas simulated the exhaust from natural gas vehicles （NGVs） operated under stoichiometric condition was investigated. The effect of La2O3 on the physicochemical properties of supports and catalysts was characterized by various techniques. The characterizations with X-ray diffraction （XRD） and Raman spectroscopy revealed that the doping of La2O3 restrained effectively the sintering of crystallite particles, maintained the crystallite particles in nanoscale and stabilized the crystal phase after calcination at 1000 ℃. The results of N2-adsorption, H2-temperatnre-programmed reduction （H2-TPR） and oxygen storage capacity （OSC） measurements indicated that La2O3 improved the textural properties, reducibility and OSC of composite supports. Activity testing results showed that the catalysts exhibit excellent activities for the simultaneous removal of methane, CO and NOx in the simulated exhaust gas. The catalysts supported on CZALa showed remarkable thermal stability and catalytic activity for the three pollutants, especially for NOx. The prepared palladium catalysts have high ability to remove NOx, CH4 and CO, and they can be used as excellent catalysts for the purification of exhaust from NGVs operated under stoichiometric condition. The catalysts reported in this work also have significant potential in industrial application because of their high performance and low cost.

Selective and mild oxidation of sulfides to sulfoxides by H_2O_2 using DBUH-Br_3 as catalyst

DBUH-Br_3 catalyzed selective conversion of sulfides to sulfoxides in the presence of H_2O_2 as oxidizing agent is described.The reaction was performed selectively at room temperature and relatively short reaction times.

Effects of Cerium Oxide on Ni/Al_2O_3 Catalysts for Decomposition of CH_4 and C_2H_4

Characteristics of carbon deposition of CH 4 and C 2H 4 decomposition over supported Ni and Ni Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal semiconductor interaction (MScI) in the Ni Ce catalyst, and the effect of MScI on the carbon deposition of CH 4 decomposition is opposite to that of C 2H 4. A novel model of carbon deposition of CH 4 or C 2H 4 decomposition was proposed.

Preparation of Sb2O3/Sb2S3/FeOOH composite photoanodes for enhanced photoelectrochemical water oxidation

A novel Sb2O3/Sb2S3/FeOOH photoanode was fabricated via a simple solution impregnation method along with chemical bath deposition and post-sulfidation.The X-ray diffractometry,Raman measurement,and X-ray photoelectron spectroscopy show that the Sb2O3/Sb2S3/FeOOH thin films are successfully prepared.SEM−EDS analyses reveal that the surface of Sb2O3/Sb2S3 thin films becomes rough after the immersion in the FeCl3 solution.The optimized impregnation time is found to be 8 h.The FeOOH co-catalyst loaded Sb2O3/Sb2S3 electrode exhibits an enhanced photocurrent density of 0.45 mA/cm2 at 1.23 V versus RHE under simulated 1 sun,which is approximately 1.41 times compared to the photocurrent density of the unloaded one.Through the further tests of UV−Vis spectroscopy,the electrochemical impedance spectra,and the PEC measurements,the enhancement can result from the increased light-harvesting ability,the decreased interface transmission impedance,and the remarkably enhanced carrier injection efficiency.

Development of antimony sulfide–selenide Sb2(S,Se)3-based solar cells

Antimony sulfide–selenide Sb2（S,Se）3,including Sb2S3and Sb2Se3,can be regarded as binary metal chalcogenides semiconductors since Sb2S3and Sb2Se3are isomorphous.They possess abundant elemental storage,nontoxicity,good stability with regard to moisture at elevated temperatures and suitable physical parameters for light absorption materials in solar cells.To date,quite a few attempts have been conducted in the materials synthesis,photovoltaic property investigation and device fabrication.Benefiting from previous investigation in thin film solar cells and new generation nanostructured solar cells,this class of materials has been applied in either sensitized-architecture or planar heterojunction solar cells.Decent power conversion efficiencies from 5%to 7.5%have been achieved.Apparently,further improvement on the efficiency is required for future practical applications.To give an overview of this research field,this paper displays some typical researches regarding the methodologies toward the antimony sulfide–selenide synthesis,development of interfacial materials and device fabrications,during which we highlight some critical findings that promote the efficiency enhancement.Finally,this paper proposes some outstanding issue regarding fundamental understanding of the materials,some viewpoints for the efficiency improvement and their future challenges in solar cell applications.

Fabrication of Gd_(2)O_(3)-doped CeO_(2)thin films through DC reactive sputtering and their application in solid oxide fuel cells

Physical vapor deposition(PVD)can be used to produce high-quality Gd_(2)O_(3)-doped CeO2(GDC)films.Among various PVD methods,reactive sputtering provides unique benefits,such as high deposition rates and easy upscaling for industrial applications.GDC thin films were successfully fabricated through reactive sputtering using a Gd_(0.2)Ce_(0.8)(at%)metallic target,and their application in solid oxide fuel cells,such as buffer layers between yttria-stabilized zirconia(YSZ)/La0.6Sr0.4Co0.2Fe0.8O_(3−δ)and as sublayers in the steel/coating system,was evaluated.First,the direct current(DC)reactive-sputtering behavior of the GdCe metallic target was determined.Then,the GDC films were deposited on NiO-YSZ/YSZ half-cells to investigate the influence of oxygen flow rate on the quality of annealed GDC films.The results demonstrated that reactive sputtering can be used to prepare thin and dense GDC buffer layers without high-temperature sintering.Furthermore,the cells with a sputtered GDC buffer layer showed better electrochemical performance than those with a screen-printed GDC buffer layer.In addition,the insertion of a GDC sublayer between the SUS441 interconnects and the Mn-Co spinel coatings contributed to the reduction of the oxidation rate for SUS441 at operating temperatures,according to the area-specific resistance tests.

Effect of erbium substitution on thermoelectric properties of complex oxide Ca_3Co_2O_6 at high temperatures

Polycrystalline particles of Ca3-xErxCo2O6 （x=0.0, 0.15, 0.3, 0.45 and 0.6） were synthesized using sol-gel method combined with Low Temperature Sintering procedure （LTS） to evaluate the effect of Er substitution on the thermoelectric properties of Ca3Co2O6. The crystal structure and microstructure were investigated using X-ray diffraction, infrared spectroscopy and scanning electron microscope. The electrical conductivity and Seebeck coefficient of the complex oxides were measured from 300 to 1073 K. The results showed that all the sampies were p-type semiconductors. The electrical conductivity increased with the increase in temperature. Er substitutions at Ca site affected carrier concentrations and carder mobility, resulting an increase in Seebeck coefficient and decrease in electrical conductivity. The power factor of Ca2.85Er0.15Co2O6 reached 10.66 μw/mK^2 at 1073 K.

Carbon dioxide reforming of methane on monolithic Ni/Al_2O_3-based catalysts

Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal （Na, K） oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.

Influence of Cr_2O_3-Al_2O_3 Composite Oxide Scale on Oxidation Resistance of ZG40Cr24

Test alloys ZG40Cr24 with alloying of 3 wt% aluminium were cast by intermediate frequency induction furnace. The oxidation resistance of test alloys at 1 000 ℃ for 500 hours was examined according to oxidation weight gain method. The scale morphology and composition were studied using scanning electron microscope （SEM） and X-ray diffraction （XRD） respectively. By energy dispersive spectroscopy （EDS） studies, a kind of composite oxide scale compounded highly by Cr2O3, Al2O3 and spinel MCr2O4 in molecule scale came into being at high temperature. With flat and compact structure, fine and even grains, such composite scale granted complete oxidation resistance to alloy ZG40Cr24. The oxidation resistance mechanism was studied deeply in electrochemistry corrosion. The P＋N semiconductor composite scale composed plenty of inner PN junctions, of which the unilateral conductive and the out-of-order arrangement endowed itself insulating in all directions. The positive and negative charges in scale could not move, and the mobile number and transferring rate of them both dropped enormously, as a result, the oxidation rate of the matrix metal was cut down greatly. So the composite scale presented excellent oxidation resistance.

Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

CO_2 methanation over TiO_2–Al_2O_3 binary oxides supported Ru catalysts

TiO_2 modified Al_2O_3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The catalytic performance of Ru/TiO_2–Al_2O_3catalyst in CO_2 methanation reaction was investigated. Compared with Ru/Al_2O_3 catalyst, the Ru/TiO_2–Al_2O_3catalytic system exhibited a much higher activity in CO_2 methanation reaction. The reaction rate over Ru/TiO_2–Al_2O_3 was 0.59 mol CO_2·(g Ru)1·h-1, 3.1 times higher than that on Ru/Al_2O_3[0.19 mol CO_2·(gRu)-1·h-1]. The effect of TiO_2 content and TiO_2–Al_2O_3calcination temperature on catalytic performance was addressed. The corresponding structures of each catalyst were characterized by means of H_2-TPR, XRD, and TEM. Results indicated that the averaged particle size of the Ru on TiO_2–Al_2O_3support is 2.8 nm, smaller than that on Al_2O_3 support of 4.3 nm. Therefore, we conclude that the improved activity over Ru/TiO_2–Al_2O_3catalyst is originated from the smaller particle size of ruthenium resulting from a strong interaction between Ru and the rutile-TiO_2 support, which hindered the aggregation of Ru nanoparticles.

Equivalent oxide thickness scaling of Al_2O_3/Ge metal-oxide-semiconductor capacitors with ozone post oxidation

Aluminum-oxide films deposited as gate dielectrics on germanium （Ge） by atomic layer deposition were post oxidized in an ozone atmosphere. No additional interfacial layer was electron microscopy and X-ray photoelectron spectroscopy detected by the high-resolution cross-sectional transmission measurements made after the ozone post oxidation （OPO） treatment. Decreases in the equivalent oxide thickness of the OPO-treated Al2O3/Ge MOS capacitors were confirmed. Furthermore, a continuous decrease in the gate leakage current was achieved with increasing OPO treatment time. The results can be attributed to the film quality having been improved by the OPO treatment.

Microstructure and dielectric properties of Ca-Al-B-Si-O glass/Al_2O_3 composites with various alkali oxides contents

The effects of alkali oxides （Na2O and K2O addition on both the sintering behavior and dielectric properties of Ca-AI-B-Si-O glass/Al2O3 composites were investigated by Fourier transform infrared spectroscopy （FTIR）, differential scanning calorimeter （DSC）, X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. The results show that the increasing amount of alkali oxides in the glass causes the decrease of [SiO4], which results in the decrease of the continuity of glass network, and leads to the decrease of the softening temperature Tf of the samples and the increasing trend of crystallization. And that deduces corresponding rise of densification, dielectric constant, dielectric loss of the low temperature co-fired ceramic （LTCC） materials and the decrease of its thermal conductivity. By contrast, the borosilicate glass/A1203 composites with 1.5% （mass fraction） alkali oxides sintered at 875 ℃ for 30 rain exhibit better properties of a bulk density of 2.79 g/cm3, a porosity of 0.48%, a 2 value of 2.28 W/（m.K）, a er value of 7.82 and a tand value of 9.1 × 10-4 （measured at 10 MHz）.

Growth of High Magnetic a-Fe2O3 and Fe3O4 Nanowires via an Oxide Assisted Vapor-Solid Process

We describes a controllable synthesis procedure for growing a-Ee2O3 and Ee3O4 nanowires. High magnetic hematite a-Fe2O3 nanowires are successfully grown on Fe0.5Ni0.5 alloy substrates via an oxide assisted vapor-solid process. Experimental results also indicate that previous immersion of the substrates in a solution of oxalic acid causes the grown nanowires to convert gradually into magnetite （Fe3O4） nanowires. Additionally, the saturated state of Fe3O4 nanowires is achieved as the oxalic acid concentration reaches 0.75 mol/L. The average diameter and length of nanowires expands with an increasing operation temperature and the growth density of nanowires accumulates with an increasing gas flux in the vapor-solid process. The growth mechanism of a-Fe2O3 and Fe3O4 nanowires is also discussed. The results demonstrate that the entire synthesis of nanowires can be completed within 2 h.

Enhancing superconductivity of ultrathin YBa2Cu3O7-δ films by capping non-superconducting oxides

In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed laser deposition.Our result shows that the termination of SrTiO3 has only a negligible effect on the properties of YBCO. In contrast, we found that capping a non-superconducting oxide layer can generally enhance the superconductivity of YBCO. PrBa2 Cu3 O7,La2 CuO4, LaMnO3, SrTiO3, and LaAlO3 have been examined as capping layers, and the minimum thickness of superconducting YBCO with capping is ~ 2 unit cells–3 unit cells. This result might be useful in constructing good-performance YBCO-based field effect devices.

NITRIC OXIDE DECOMPOSITION ON ALKALI-PROMOTED Pd/AL_2o_3 CATALYSTS

Alkali-promoted Pd/Al2O3 catalysts exhibit much higher activities in NO decomposition than Pd/Al2O3. FTIR study shows that on the alkali promoted catalyst.nitric oxide exists on the surface mainly in negatively charged form(NO-)at high temperatures.which is consistent with the activity improvement.