X-ray Spectroscopically Probing Mo_(2)C@MoSe_(2)Heterojunction Electrodes

Due to their high electrical conductivity and layered structure,two dimensional MXene materials are re⁃garded as promising candidates for energy storage applications.However,the relatively low stability and specific ca⁃pacity of MXene materials limit their further utilization.In this study,these issues are addressed using a heterostruc⁃ture strategy via a one-step selenization method to form Mo_(2)C@MoSe_(2).Synchrotron radiation X-ray spectroscopic and high-resolution transmission electron microscopy(HRTEM)characterizations revealed the heterostructure consisting of in-situ grown MoSe_(2)on Mo_(2)C MXene.Electrochemical tests proved the heterojunction electrode’s superior rate perfor⁃mance of 289.06 mAh·g^(-1)at a high current density of 5 A·g^(-1)and long cycling stability of 550 mAh·g^(-1)after 900 cycles at 1 A·g^(-1).This work highlights the useful X-ray spectroscopic analysis to directly elucidate the heterojunction structure,providing an effective reference method for probing heterostructures.

Extraction of nickel from molybdenum leaching residue of metalliferous black shale by segregation roasting and acid leaching

The recovery of nickel from molybdenum leach residue by the process of segregation roasting-sulfuric acid leaching-solvent extraction was investigated. The residue was characterized by microscopic investigations, using X-ray fluorescence spectrometry （XRF） and X-ray diffractometry （XRD） techniques and the residue after segregation roasting was characterized by chemical phase analysis method. A series of experiments were conducted to examine the mass ratio of activated carbon （AC） to the residue, segregation roasting time and temperature, sulfuric acid concentration, liquid-to-solid ratio, leaching time, leaching temperature, addition amount of 30% H2O2, stirring speed （a constant） on the leaching efficiency of nickel. A maximum nickel leaching efficiency of 90.5% is achieved with the mass ratio of AC to the residue of 1：2.5, segregation roasting time of 2 h, segregation roasting temperature of 850 ℃, sulfuric acid concentration of 4.5 mol/L, liquid-to-solid ratio of 6：1, leaching time of 5 h, leaching temperature of 80 ℃, addition of 30% H202 of 0.6 mL for 1 g dry residue. Under these optimized conditions, the average leaching efficiency of nickel is 89.3%. The nickel extraction efficiency in the examined conditions is about 99.6%, and the nickel stripping efficiency in the examined conditions is about 99.2%.

Coexistence of antiferromagnetic and ferromagnetic in Mn-doped anatase TiO_2 nanowires

A series of Mn-doped TiO2 nanowires(NWs) were prepared by hydrothermal method at the mole fraction of Mn changing from 0 to 12.0%.X-ray powder diffraction(XRD) analysis shows that all the samples have pure anatase structure.SEM and TEM studies show that the diameter and the length of the Mn-doped TiO2 NWs are larger than those of the undoped TiO2 NWs.Energy dispersive X-ray spectroscopy(EDX) reveals that the samples are composed of Ti,Mn and O.According to magnetization measurements,all samples show ferromagnetic behavior,but only the undoped TiO2 NWs are completely ferromagnetic with a saturated magnetization about 1.0 mA·m2/kg.Mn-doped TiO2 samples exhibit antiferromagnetic and ferromagnetic(AF-FM) behaviors simultaneously.Photoluminescence(PL) spectra demonstrate the existence of MnO2 sublattice.These observations indicate that an AF-WF crossover is induced by the coexistence of TiO2 sublattice and MnO2 sublattice.

同步辐射X射线磁二色性在自旋电子学研究中的应用

文章对同步辐射X射线磁圆二色谱和X射线磁线二色谱的独特优点进行了综合分析,并通过一些典型应用实例说明同步辐射磁性测量技术具有元素分辨能力、高灵敏度、纳米量级空间分辨能力和皮秒量级时间分辨能力,并可用于测量铁磁性和反铁磁性,因而在自旋电子学材料和器件研究领域具有广泛的应用前景.

神光Ⅱ黑腔等离子体时间分辨的电子温度诊断

在神光Ⅱ强激光装置上,用条纹晶体谱仪对埋点于黑腔靶内壁上的双示踪Ti和Cr材料的激光等离子体高离化态离子发射的X射线谱线进行实验测量,获得超高时间分辨的X射线细致结构谱线。用碰撞辐射模型计算了非局域热动平衡的等离子体布居数,组态平均速率系数由一级微扰理论计算,电子波函数由Hartree-Fock Slater自洽场方法计算,给出了Ti和Cr激光等离子体在电子密度为1019~1022cm-3范围内的He-α线强比与电子温度的关系曲线。采用等电子X射线谱线法,获得了黑腔靶激光等离子体冕区的电子温度随激光脉冲加热从低温到高温、然后缓慢下降的演化过程,其峰值达到2.05 keV。

从不同的方向检测NaCl单晶体结构的研究

利用X衍射仪,研究(100),(110),(111)晶面的NaCl单晶,对其特征谱线做了分析,得出各个晶体的晶面间距.发现(100)晶面很好的切割了NaCl离子晶体,并对各个晶面的NaCl单晶特征峰的进行了比较,分析了衍射峰不同的原因.

莫塞莱与原子序数规律

英国早逝的物理学家莫塞莱在去世前的两年对物理学界所做的贡献,证明原子中的电子数正是元素周期表中的原子序数,并且发现了原子光谱谱线频率和原子序数之间的关系,也就是莫塞莱定律。本文简述了莫塞莱生平,回顾了莫塞莱通过测量不同金属发出的X射线的波长,发现原子序数和辐射频率的关系,并指出原子序数才是原子最本质的属性。他的杰出贡献在原子物理学的发展史上产生了深刻影响。

Visible-Light Activities of Erbium Doped BiVO4 Photocatalysts

Er-doped BiVO4 composite photocatalyst was hydrothermal synthesized and characterized by X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray Spectroscopy, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectra techniques. The activity of the catalyst was determined by oxidative decomposition of methyl orange in aqueous solution under visible-light irradiation. X-ray photoelectron spectroscopy and energy-dispersive X-ray Spectroscopy analysis revealed that the doped Er existed in the form of Er2O3. It also showed that the Er doping can enhance the visible-light absorption abilities of catalysts and their visible-light-driven photocatalytic activities in comparison with those of pure BiVO4.

Catalytic performance and kinetics of Au/γ-Al_2O_3 catalysts for low-temperature combustion of light alcohols

Au/γ-Al2O3 catalysts were prepared by deposition-precipitation method for the catalytic combustion of low concentration alcohol streams(methanol,ethanol,iso-propanol and n-propanol).The catalysts were characterized by X-ray photoelectron spectroscopy(XPS),X-ray diffractometry(XRD) and energy dispersive X-ray micro analysis(EDS) techniques.The XPS results showed that there was only Au0 on the surface of catalysts.The XRD patterns showed that Au was presumably highly dispersed over γ-Al2O3.The temperatures for complete conversion of methanol,ethanol,iso-propanol and n-propanol with concentration of 2.0 g/m3 were 60,155,170 and 137 ℃,respectively,but they were completely mineralized into CO2 and H2O at 60,220,260 and 217 ℃ respectively over the optimized catalyst.The activity of the catalyst was stable in 130 h.The kinetics for the catalytic methanol elimination followed quasi-first order reaction expressed as r=0.652 8c0+0.084 2.The value of apparent activation energy is 54.7 kJ/mol in the range of reaction temperature.

Conversion of CO2 by non-Thermal Inductively-Coupled Plasma Catalysis

CO2 decomposition is a very strongly endothermic reaction where very high temperatures are required to thermally dissociate CO2.Radio frequency inductively-coupled plasma enables to selectively activate and dissociate CO2 at room temperature.Tuning the flow rate and the frequency of the radio frequency inductively-coupled plasma gives high yields of CO under mild conditions.Finally the discovery of a plasma catalytic effect has been demonstrated for CO2 dissociation that shows a significant increase of the CO yield by metallic meshes.The metallic meshes become catalysts under exposure to plasma to activate the recombination reaction of atomic O to yield O2,thereby reducing the reaction to convert CO back to CO2.Inductively-coupled hybrid plasma catalysis allows access to study and to utilize high CO2 conversion in a non-thermal plasma regime.This advance offers opportunities to investigate the possibility to use radio frequency inductively-coupled plasma to store superfluous renewable electricity into high-valuable CO in time where the price of renewable electricity is plunging.

Dissolution mechanism and solubility of hemimorphite in NH_3-(NH_4)_2SO_4-H_2O system at 298.15 K

The dissolution mechanism of hemimorphite in NH3-（NH4）2SO4-H2O system at 298.15 K was investigated by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS） analysis. The results show that hemimorphite is soluble in NH3-（NH4）2SO4-H2O system and its residue exists in the form of an amorphous SiO2 layer on the hemimorphite surface. The XPS data also indicate that the Si 2p3/2 and O ls spectra of the hemimorphite are broadened and shift to higher binding energies and their binding energies are closer to silica with an increase of total ammonia and time. Solubility of hemimorphite in NH3-（NH4）2SO4-H2O system was measured by means of isothermal solution method at 298.15 K based on the study of the dissolution mechanism of hemimorphite. The results show that the solubility of zinc in solution increases firstly and then decreases with the increase of cr（NH3） （total ammonia concentration） at different NH3/NH4^＋ ratios. The solubility of silicon in solution decreases from 0.0334 mol/kg in ct（NH3）-4.1245 mol/kg NH3-（NH4）2SO4-H2O solution to 0.0046 mol/kg in cT（NH3）=7.6035 mol/kg NH3-（NH4）2SO4-H2O solution.

Gold-doping of carbon-supported palladium improves reduction catalysis

Bimetallic palladium-gold （PdAu） catalysts have better catalytic performance than monometallic catalysts for many applications. PdAu catalysts with controlled nanostructures and enhanced activi- ties have been extensively studied but their syntheses require multiple and occasionally complicated steps, In this work, we demonstrated that supported PdAu catalysts could be simply prepared by doping a supported Pd catalyst with gold through wet impregnation and calcination. Resulting PdAu-on-carbon （PdAu/C） catalysts were tested for the room-temperature, aqueous-phase hydro- dech/orination of trichloroethene. The most active PdAu/C catalyst （Pd 1.0 wt%, Au 1.1 wt%, dried/air/H2 process] had an initial turnover frequency （TOF] of 34.0×10^-2 mOITcE mOled-1 S-1, which was 〉15 times higher than monometallic Pd/C （Pd 1,0 wt%, initial TOF of 2.2 ×10^-2 molTCE molpd^-1s^-1）. Through X-ray absorption spectroscopy, the gold kept Pd from oxidizing under calcination at 400℃. Probable nanostructure evolution pathways are proposed to explain the observed catalysis,

Preparation and Visible-Light Photocatalytic Activity of FeTPP-Cr-TiO2 Microspheres

Tetraphenyl-porphyrin iron （FeTPP） was chosen to sensitize Cr doped TiO2 （Cr-TiO2） nanoparticles, a novel multimodified photocatalyst FeTPP-Cr-TiO2 with excellent visible- light photocatalytic activity was successfully synthesized. The FeTPP-Cr-TiO2 microspheres were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electronic microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectra and N2 adsorption-desorption isotherms. The photocatalytic activity of FeTPP-Cr-TiO2 was evaluated by degradations of methylene blue in aqueous solution under irradiation with Xe lamp （150 W）. The results showed that the FeTPP-Cr-TiO2 multimodified photocatalyst was anatase phase with high specific surface area （74.7 m^2/g）, and exhibited higher photocatalytic degradation efficiency than Cr-TiO2 and FeTPP-TiO2. The photocatalytic degradations of three quinolone antibiotics （lomefioxacin, norfioxacin, and ofioxacin） were further estimated for the feasibility of practical application of catalyst in wastewater treatment. It is desirable that photodegradation of antibiotics with FeTPP-Cr-TiO2 achieved pretty high degradation rates and all followed the pseudo first-order reaction model, and the rate constants k of 3.02×10^-2, 2.81×10^-2, and 3.86×10^-2 min-1 and the half-lifes t1/2 of 22.9, 24.6, and 17.9 min were achieved respectively.

High-strength composite yarns derived from oxygen plasma modified super-aligned carbon nanotube arrays

Spinning carbon nanotube （CNT） yarns from super-aligned carbon nanotube （SACNT） arrays is a promising approach to fabricate high-strength fibers. However the reported tensile strengths of the as-prepared fibers are far below that of an individual CNT. It is therefore still a challenge to improve their mechanical strengths. Here we report that the tensile strengths and Young＇s moduli can be further improved to 2.2 GPa and 200 GPa respectively, if we first treat the SACNT array with oxygen plasma by using a reactive ion etching （RIE） facility, then dry spin yarns from it and make composite fibers with polyvinyl alcohol. According to the experimental results obtained using scanning electron microscopy （SEM）, Raman spectroscopy and X-ray photoelectron spectroscopy （XPS）, the improvement is attributed to the oxygen RIE process, as it can create functional groups on the outer walls of CNTs and thus improve the interaction between the CNTs and the polymer molecules.

Enhanced electro-oxidation of formic acid by a PdPt bimetallic catalyst on a CeO_2-modified carbon support

PdPt bimetallic catalysts that employ CeO2-modified carbon black as a support have been prepared using an organic colloidal method. PdPt/CeO2-C shows excellent performance toward the anodic oxidation of formic acid. The effects of varying both Pd to Pt ratio and CeO2 content have been investigated. The optimal Pd to Pt atomic ratio is 15, indicating that addition of small amounts of Pt can significantly enhance the activity of the catalyst. When the CeO2 content in the catalyst reaches as high as ~15 wt.%, the catalyst shows the maximum activity. Adding CeO2 not only enhances the catalytic activity of the material, but may also change the mechanism of its catalysis of the anodic oxidation of formic acid. PdlsPh/15CeO2-C exhibited 60% higher activity than Pd/C, and had a negative shift in onset potential of more than 0.1 V. Based on characterization by X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and transmission electron microscopy, the interactions between the components are revealed and discussed in detail.

Nitrogen-doped graphene supported Pd@PdO core- shell clusters for C-C coupling reactions

The introduction of nitrogen significantly decreases the metal particle size and improves the performance of metal-based graphene-supported catalysts. In this work, the density functional theory is used to understand the interaction between nitrogen-doped graphene and Pd@PdO clusters. Experiments show that small size Pd@PdO clusters （1-2 nm） can be grown uniformly on nitrogen-doped graphene sheets by a facile oxidation-reduction method. The nanoscale interaction relationship between nitrogen-doped graphene and Pd@PdO clusters is investigated through X-ray photoelectron spectroscopy （XPS） and X-ray absorption spectra （XAS）. The composite catalysts are applied in Suzuki-Miyaura reactions giving high yields and good structural stability. These results have potential impact in design and optimization of future high performance catalyst materials for cross coupling reactions.

Size-controlled chalcopyrite CuInS_2 nanocrystals:One-pot synthesis and optical characterization

Chalcopyrite ternary CulnS2 semiconductor nanocry stals have been synthesized via a facile one-pot chemical approach by using oleylamine and oleic acid as solvents. The as-prepared CuInS2 nanocrystals have been characterized by instrumental analyses such as X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, transmission electron microscopy （TEM）/high-resolution TEM （HRTEM）, energy-dispersive X-ray spectroscopy （EDS）, UV-vis absorption spectroscopy （UV-vis） and photoluminescence （PL） spectroscopy. The particle sizes of the CuInS2 nanocrystals could be tuned from 2 to 10 nm by simply varying reaction conditions. Oleylamine, which acted as both a reductant and an effective capping agent, plays an important role in the size-controlled synthesis of CulnS2 nanocrystals. Based on a series of comparative experiments under different reaction conditions, the probable formation mechanism of CulnS2 nanocrystals has been proposed. Furthermore, the UV-vis absorption and PL emission spectra of the chalcopyrite CulnS2 nanocrystals have been found to be adjustable in the range of 527-815 nm and 625-800 rim, respectively, indicating their potential application in photovoltaic devices.

Nano CuO/ZSM-5 zeolite as a green and efficient catalyst for dehydration of 1,4-butanediol to tetrahydrofuran

Nano CuO/ZSM-5 zeolite was prepared and used as a catalyst for dehydration of 1,4-butanediol(BDO) to tetrahydrofuran(THF) in liquid-phase. It was found that the 4.6 wt% CuO/ZSM-5 displayed good catalytic performance, and nearly 100%of BDO conversion and more than 99% of THF selectivity could be achieved by a rotary evaporator reactor at 170 °C under the atmospheric pressure. With such mild reaction conditions, 2400 g BDO could be converted to THF over 1 g catalyst under semi-continuous operation. Characterizations with X-ray diffraction(XRD), temperature-programmed reduction(TPR),NH3-temperature programmed desorption(TPD), X-ray photoelectron spectroscopy(XPS), transmission electron microscope(TEM) and Brunauer-Emmett-Teller(BET) over fresh and used 4.6 wt% CuO/ZSM-5 were conducted. Based on the results of the characterization and catalytic performance of 4.6 wt% CuO/ZSM-5, it can be conjectured that the formed 1–3 nm CuO nanoparticles, suitable acidity of the catalyst due to the synergic interaction of CuO and ZSM-5 support promoted the dehydration of BDO to THF.

Green and low temperature synthesis of nanocrystalline transition metal ferrites by simple wet chemistry routes

Crystalline and nanostructured cobalt （CoFe2O4）, nickel （NiFe2O4）, zinc （ZnFe2O4） and manganese （MnFe2O4） spinel ferrites are synthesized with high yields, crystallinity and purity through an easy, quick, reproducible and low-temperature hydrothermal assisted route starting from an aqueous suspension of copredpitated metal oxalates. The use of water as a reaction medium is a further advantage of the chosen protocol. Additionally, the zinc spinel is also prepared through an alternative route combining copredpitation of oxalates from an aqueous solution with thermal decomposition under reflux conditions. The nanocrystalline powders are obtained as a pure crystalline phase already at the extremely low tem- perature of 75 ℃ and no further thermal treatment is needed. The structure and microstructure of the prepared materials is investigated by means of X-ray powder diffraction （XRPD）, while X-ray photoelectron spectroscopy （XPS） and inductively coupled plasma-atomic emission spectroscopy （ICP-AES） analyses are used to gain information about the surface and bulk composition of the samples, respectively, confirming the expected stoichiometry. To investigate the effect of the synthesis protocol on the morphology of the obtained ferrites, transmission electron microscopy （TEM） observations are performed on selected samples. The magnetic properties of the cobalt and manganese spinels are also investigated using a superconducting quantum device magnetometer （SQUID） revealing hard and soft ferrimagnetic behavior, respectively.

Enhanced photoelectrochemical and photocatalytic activities of CdS nanowires by surface modification with MoS_2 nanosheets

Nanocomposites composed of one-dimensional（1D） CdS nanowires（NWs） and 1 T-MoS2 nanosheets have been fabricated through a two-step solvothermal process. 5 mol% of MoS2 loading results in the best optical properties,photoelectrochemical（PEC） as well as photocatalytic activities for hydrogen evolution reaction（HER）. Compared with pure CdS NWs, the optimized nanocomposite shows 5.5 times enhancement in photocurrent and 86.3 times increase for HER in the presence of glucose and lactic acid as hole scavengers.The enhanced PEC and HER activities are attributed to the intimate contact between MoS2 and CdS that efficiently enhances charge carrier separation. In addition, ultrafast transient absorption（TA） measurements have been used to probe the charge carrier dynamics and gain deeper insight into the mechanism behind the enhanced PEC and photocatalytic performance.