In situ construction of oxygen-vacancy-rich Bi~0@Bi_2WO_(6-x) microspheres with enhanced visible light photocatalytic for NO removal

Surface oxygen vacancy defects and metal deposition on semiconductor photocatalysts play a critical role in photocatalytic reactions.In this work,oxygen-deficient Bi_2WO_6 microspheres have been prepared by a facile ethylene glycol-assisted solvothermal method.Bi~0 nanoparticles were reduced by in situ thermaltreatment on Bi_2WO_6 microspheres to obtain Bi~0@Bi_2WO_(6-x) as well as maintaining the oxygen vacancies(OVs) under N_2 atmosphere.Afterwards,photocatalytic NO oxidation removal activities of these photocatalysts were investigated under visible light irradiation and Bi~0@Bi_2WO_(6-x) shows the best NO removal activity than other samples.The photogenerated cha rge separation and trans fe r are promoted by Bi~0 nanoparticles deposited on the surface of semiconductor catalysts.OVs defects promote the activation of reactants(H_2 O and O_2),thereby enhancing the formation of the active substance.Moreover,both OVs defects and Bi~0 metal have the characteristics of extending light absorption and enhancing the efficient utilization of solar energy.Besides,the photocatalytic NO oxidation mechanism of Bi~0@Bi_2WO_(6-x)was investigated by in situ FTIR spectroscopy for reaction intermediates and final products.This work furnishes insight into the synthesis strategy and the underlying photocatalytic mecha nism of the surfacemodified Bi~0@Bi_2WO_(6-x) composite for pollutants removal.     

Upconversion Luminescence Properties of NaY_(0.92)Yb_(0.05)Er_(0.03)F_4 Enhanced by Zr~(4+) Codoping

In this paper we present a novel report on the upconversion luminescence performance of NaY_(0.92)Yb_(0.05)Er_(0.03)F_4 enhanced by Zr~(4+) codoping. The luminescence intensity of the tridoped hexagonal NaYF_4 synthesized by a hydrothermal method increased to the maximum, about seven times of the non-Zr~(4+) sample when the Zr~(4+) codoping concentration rose to 6 mol%, while the luminescence lifetime was also prolonged by Zr~(4+) codoping. To explore the relationships between the microstructure and upconversion properties, X-ray powder diffraction, field emission scanning electron microscope, electron energy-dispersive spectroscopy and upconversion emission spectroscopy were employed. From these characterizations, we found that the codoping of Zr~(4+) could modulate the crystal microstructure of NaYF_4 for higher upconversion luminescence intensity and longer lifetime. This study may be helpful for the design and synthesis of high-performance upconversion materials.     

Fabrication of HRP/Bi_2WO_6 photoenzyme-coupled artificial catalytic system for efficiently degrading bisphenol A

A novel photoenzyme-coupled artificial catalytic system is fabricated by immobilizing horseradish peroxidase(HRP) on the Bi_2WO_6 hollow nanospheres via a facile electrostatic self-assembly process. The obtained Bi_2WO_6/HRP sample not only improves the visible light harvest ability but also promotes the high-efficiency separation of charge carriers. More importantly, the photogenerated electrons and produced H_2O_2 on Bi_2WO_6 directly take part in redox cycle reactions of HRP to induce photoenzyme synergic catalytic effect. In consequence, the degradation activity of Bi_2WO_6/HRP is significantly improved relative to Bi_2WO_6 and HRP for removing bisphenol A(BPA) under the visible light irradiation.This work launches a feasible design strategy for exploiting photoenzyme-coupled artificial catalytic system with special structure to degrade organic pollutants in water efficiently.     

Rapid Microwave-assisted Hydrothermal Synthesis of Bi_(0.76)Sb_(1.24)S_3 and Its Application in the Photocatalytic Degradation of Pollutants by Visible Light Irradiation

Bi_(0.76)Sb_(1.24)S_3 nanocrystals were synthesized by a rapid microwave-assisted hydrothermal method using bismuth nitrate, antimony pentoxide and thioacetamide as starting materials and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and UV-vis diffuse reflectance spectroscopy(DRS). The effects of the synthetic condition on the product composition were investigated. The photocatalytic activities of Bi_(0.76)Sb_(1.24)S_3 nanocrystals for the degradation of methyl orange and p-hydroxyazobenzene under visible light irradiation were evaluated. Bi_(0.76)Sb_(1.24)S_3 exhibited good and stable visible light photocatalytic activity.     

MgWO_4:Nd~(3+)的水热合成及近红外发光性能研究

采用水热法制备MgWO_4:Nd~(3+)近红外发光材料.通过XRD,SEM和发光光谱等手段对样品的物相、形貌、发光性质进行表征.XRD测试结果表明:水热法制备MgWO_4:Nd~(3+)在850℃以上煅烧时,四方晶系转变为单斜晶系;1050℃煅烧后,sEM显示样品形貌由片状变为棒状且分散良好;激发和发射光谱的对比研究表明,MgWO_4:Nd~(3+)中WO_4~(2-)对Nd~(3+)存在有效的能量传递.研究了Nd~(3+)的掺杂量、煅烧温度、煅烧时间对材料近红外发光的影响.结果表明:在1050℃煅烧时,Nd~(3+)掺杂量为0.5%时发光最强;随着煅烧温度的升高,MgWO_4:Nd~(3+)的近红外发光强度先增强后减弱,而煅烧时间对发光强度影响很小.     

Synthesis, Characterization, and Photocatalytic Activity of Bi_2O_3

A series of Bi2O3 were prepared by a facile hydrothermal method using NaOH and ammonia as the mineralizers. The products were characterized by XRD, IR, UV-vis diffuse reflectance spectra, and photodegradation of Rhodamine B dye. Simply using NaOH to supply a strong base condition, single phase α-Bi2O3 was formed. When changing the amount of NaOH and ammonia, mixed phases of α-Bi2O3, （BiO）4CO3（OH）2 and Bi2O2CO3 were obtained. All samples were found to show photocatalytic activities towards the degradation of Rhodamine B dye under UV light irradiation, in which mixed phase samples showed higher activities than single phase α-Bi2O3 possibly owing to the synergistic effect of the mixed phases.     

ZrO_2表面上Zr~(3+)中心上的O_2吸附平衡

以ESR为主要研究手段,研究了一种最可几粒径为9.8 nm的ZrO_2样品在室温不 同气体（He,H_2,O_2,空气,温空气）中及经不同温度处理后ZrO_2中Zr~(3+)中 心信号的变化。根据ZrO_2样品中Zr~(3+)浓度在室温下对于介质气体中O_2分压改 变的响应极快及Zr~(3+)浓度在室温下对于介质气体变化可逆性等特点提出, ZrO_2中Zr~(3+)中心绝大多数存在于样品的表面上,Zr~(3+)是ZrO_2晶体表面上那 些O~(2-)配位不饱和的Zr原子点位。ZrO_2表面上ESR活性Zr~(3+)中心的数目与其 上氧吸附平衡有关。由ESR法对ZrO_2样品中Zr~(3+)中心的定量和对ZrO_2晶体的粒 度分析,推测ZrO_2表面上Zr~(3+)中心是那些位于ZrO_2微晶的晶角处O~(2-)配位 不饱和的Zr原子。     

球磨法制备异质结型光催化剂ZnO/Bi_4Ti_3O_(12)及催化性能

本文用水作为分散介质,掺杂一定量的ZnO于Bi_4Ti_3O_(12)中,采用高能球磨法制备了异质结型光催化剂ZnO/Bi_4Ti_3O_(12).利用UV-Vis、XRD、SEM和PL等仪器对样品进行了分析与表征.以375 W中压汞灯为光源,通过对亚甲基蓝的氧化来研究其光催化活性.结果表明,对于光氧化亚甲基蓝(MB),异质结型光催化剂ZnO/Bi_4Ti_3O_(12)光催化活性高于钛酸铋的光催化活性.当ZnO的掺杂量分别是0.0和0.5wt.%,异质结型光催化剂ZnO/Bi_4Ti_3O_(12)对亚甲基蓝光氧化率分别达到50.2和80.3 %.     

铁酸铋的水热合成及其光催化性能

以Fe(NO_3)_3·9H_2O和Bi(NO_3)_3·5H_2O为原料,NaOH为矿化剂,用水热法合成了柱状晶体Bi_2Fe_4O_9,其结构和催化性能经XRD,SEM和UV-Vis表征.结果表明,Bi_2Fe_4O_9截面边长约500 nm,长约2μm～3μm,分散均匀.Bi_2Fe_4O_9在可见光区域有较强吸收,对甲基橙降解效果较好.     

铬和钼掺杂对HCa2Nb3O10/Pt光催化性能的影响

通过高温固相反应合成了铌酸盐KCa2Nb3O10及Cr3+和Mo6+掺杂(摩尔分数5%)的KCa2Nb3O10,并通过离子交换反应制备出HCa2Nb3O10及Cr3+和Mo6+掺杂的HCa2Nb3O10,采用X射线衍射、原子吸收光谱、扫描电镜等对所制得的样品进行了表征.在甲醇为电子给体、Pt为助催化剂的情况下,研究了催化剂HCa2Nb3O10及Cr3+和Mo6+掺杂的HCa2Nb3O10在紫外光辐射下分解水产氢的光催化活性,并讨论了引起催化剂活性差异的原因.     

Efficient fabrication of ZrO2-doped TiO2 hollow nanospheres with enhanced photocatalytic activity of rhodamine B degradation

ZrO(2)-doped TiO(2) hollow nanospheres with anatase phase are efficiently fabricated via functionalized negatively charged polystyrene (PS) spheres without any surfactant or polyelectrolyte. The resulting Ti(1-)(x)Zr(x)O(2) (hereafter denoted as TZ) hollow nanospheres are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF), nitrogen sorption, and UV-vis diffuse reflectance spectroscopy (UV-vis). The Zr(4+) incorporation decreases the anatase crystallite size, increases the specific surface area, and changes the pore size distribution. Furthermore, it induces enrichment of electron charge density around Ti(4+) ions and blueshift of absorption edges. The TZ hollow nanospheres doped with moderate ZrO(2) (molar ratio, Ti:Zr=10:1) exhibit better photocatalytic activity than the other samples for the degradation of rhodamine B in aqueous solution, which is correlated with the effect of Zr(4+) doping on the physicochemical properties in terms of surface structures, phase structures, and the electronic structures.     

Ce(4+) doped TiO<Subscript>2</Subscript> thin films: Characterization and photocatalysis

Undoped and Ce(4+) doped TiO₂ thin films were prepared by sol-gel method. The samples were characterized using scanning electron microscopy, the photocatalytic reactivity was evaluated by degradation of methylene blue in the aqueous solution. 0.5 wt. % Ce(4+) doped TiO₂ thin films calcined at 400°C show the highest photocatalytic activity. The text was submitted by the authors in English.     

钙的加入对含锆熔铁型氨合成催化剂性能的影响

近年来，对于熔铁型氨合成催化剂在不断通过加入新的助剂来改善其性能。本文用Mossbauer谱等手段分析与研究加入钙后对含锆催化剂的影响。     

Controlled Synthesis and Optical Properties of Lanthanide-doped Na_3ZrF_7 Nanocrystals

In this paper,we report for the first time the controlled synthesis of lanthanide ion(Ln~(3+))-doped tetragonal-phase Na_3Zr F_7 nanocrystals(NCs)via a high-temperature co-precipitation approach.The as-synthesized Na_3Zr F_7 NCs are systematically studied by utilizing the XRD,TEM as well as high-resolution photoluminescence(PL)spectroscopy.The morphology and size for the as-synthesized Na_3Zr F_7 NCs can be finely controlled by changing the experimental parameters such as the amount of precursor,solvent ratio,reaction temperature and time.By utilizing the red-emitting Eu~(3+)ion as an efficient optical/structural probe,the successful hetero-valence doping of Ln~(3+)activators in the lattices of Na_3Zr F_7 NCs is well-established regardless of their different valences and radii between host Zr~(4+)ion and Ln~(3+)dopant.As a result,intense upconversion(UC)luminescence(UCL)ranging from UV to visible and to NIR spectral regions can be readily achieved after the doping of typical UCL couples of Yb~(3+)/Er~(3+),Yb~(3+)/Tm~(3+)and Yb~(3+)/Ho~(3+)into the lattices of Na_3Zr F_7 NCs when excited by using a 980-nm NIR diode laser.     

氮自掺杂暴露（001）晶面TiO2微米片的可见光光催化CO2还原性能增强

化石能源的使用可产生大量CO2,带来严重的温室效应。光催化CO2还原生产太阳燃料技术既有望缓解温室效应,又可以将低能量密度的太阳能转化为高能量密度的化学能储存起来方便使用。高效光催化材料的开发是发展光催化技术的关键。迄今,在已开发的所有半导体光催化材料中, TiO2仍是广泛研究的明星材料。在实际使用中, TiO2的光催化效率仍受限于其极弱的可见光利用率和较高的电子-空穴复合几率。近年来,越来越多的研究表明TiO2的结构与形貌特征极大地影响其光催化效率。尤其, TiO2的外露晶面设计与晶面效应研究引起了广泛关注。由于具有较高表面能和较多表面不饱和键,起初大多数理论和实验研究认为锐钛矿TiO2(001)晶面是光催化活性晶面。后来,越来越多研究表明并非锐钛矿TiO2(001)晶面的暴露比例越高其光催化活性就越高。最近,我们发现锐钛矿TiO2(001)晶面与(101)晶面在调控光催化CO2还原性能上具有良好的协同效应。密度泛函理论计算表明,锐钛矿TiO2的(001)晶面与(101)晶面的能带结构有差异,(001)晶面的导带位置相对于(101)晶面而言较高,而(101)晶面的价带位置相对于(001)晶面而言较低。基于此我们提出,具有合适比例的锐钛矿TiO2的(001)晶面与(101)晶面的交界处可以形成最佳的表面异质结或晶面异质结。表面异质结的形成导致光生电子倾向于向(101)扩散,光生空穴倾向于向(001)扩散,从而促进光生电子-空穴分离,降低光生电子-空穴复合几率。在此工作基础上,我们直接以氮化钛为原料,氢氟酸为添加剂,通过简单的水热反应一步合成了氮自掺杂的TiO2微米片。利用X射线粉末衍射、扫描电镜、X射线光电子能谱、紫外-可见漫反射光谱、氮气吸附-脱附以及电化学阻抗谱等方法手段对所制备的光催化剂进行了基本结构与理化性质表征分析,并研究了其可见光光催化CO2还原性能。电镜照片结果表明,我们所制备的氮自掺杂锐钛矿TiO2微米片的(001)晶面与(101)晶面比例分别为65%和35%。基于我们前期研究结果, TiO2微米片的(001)晶面与(101)晶面可以形成表面异质结,具有良好的电荷分离效率,这也得到了电化学阻抗谱研究结果的证明。同时,由于N的原位掺杂,所制备的TiO2微米片具有优异的可见光捕获能力。由于可见光利用效率增强与光生电子-空穴分离效率提高这两方面的综合作用,所制备的氮自掺杂TiO2微米片具有非常好的可见光光催化CO2还原制甲醇性能,比商用P25及氮掺杂TiO2纳米粒子等参考样品的可见光光催化性能更优异。研究表明,通过原位自掺杂方法与晶面设计方法相结合,可以同时改善TiO2的可见光利用效率和光生电子-空穴分离效率,优化TiO2的可见光光催化性能,这也为后续开发新型高效光催化材料提供了新思路。     

Zn-TiO2/AC复合催化剂的制备及其光催化活性

以硝酸锌、钛酸四丁酯和活性炭为原料,采用真空吸附法制备了不同组成的Zn TiO₂/AC.通过X射线衍射(XRD)和透射电镜(TEM)对催化剂进行了表征.选择较难降解的Cl₃CCOOH作为探针分子考察了其光催化活性.结果表明,掺锌能提高TiO₂/AC的催化活性,当Zn的摩尔分数为0.5%(相对TiO₂)、处理温度为400℃,溶液的pH值为6时,Zn TiO₂/AC催化剂具有很好的光催化活性.     

Effect of doped zinc species on the photocatalytic activity of gallium oxide for hydrogen production

Zn-doped Ga(2)O(3) samples were prepared by a homogeneous precipitation (HP) method, and the local structures of Zn ions and their photocatalytic activities for hydrogen production were examined. In the sample with low doping amount, the Zn(2+) ions substituted for the Ga(3+) ions in the Ga(2)O(3) photocatalyst and enhanced the photocatalytic activity, since they would improve the migration of the photoexcited electrons in the conduction band of the Ga(2)O(3) photocatalyst. In the sample with high doping amount, the Zn ions formed a composite ZnGa(2)O(4) phase in the bulk of the Ga(2)O(3) photocatalyst to decrease the photocatalytic activity in the present reaction.     

The effect of group IIIA metal ion dopants on the photocatalytic activities of nanocrystalline Sr0.25H1.5Ta2O6·H2O

A series of group IIIA metal ion electron acceptors doped into Sr(0.25)H(1.5)Ta(2)O(6)·H(2)O (HST) samples have been prepared by an impregnation and calcination method for the first time. The samples are characterized by XRD, TEM, DRS and XPS. The variations in the electronic structure and photoelectric response after metal ion doping are investigated by theoretical calculations and photocurrent experiments, respectively. Results show that the metal ions can be efficiently incorporated into the HST crystal structure, which is reflected in the lattice contraction. Meanwhile, the photoabsorption edges of the metal-doped HST samples are red shifted to a longer wavelength. Taking into account the ionic radii and electronegativities of the dopants, as well as the XRD and XPS results, it is concluded that Ta(5+) ions may be partially substituted by the Al(3+) and Ga(3+) ions in the framework, while In(3+) ions are the favourable substitutes for Sr(2+) sites in the cavity. The first-principles DFT calculations confirm that the variation of the band structure is sensitive to the type of group IIIA metal ion. Introducing the dopant only at the Ta site induces an obvious variation in the band structure and the band gap becomes narrow. Meanwhile, an 'extra step' appeared in the band gap, which can trap photogenerated electrons from the valance band (VB) and could enhance the charge mobility and the photocurrent. For the photocatalytic degradation of methyl orange in an aqueous solution and in benzene in the gas phase, the doped samples show superior photocatalytic activities compared with both undoped samples and TiO(2). The enhanced photocatalytic activities can be well explained by their electronic structure, photoabsorption performance, photoelectric response, and the concentration of the active species. Due to the fact that Ga ion doping can create an acceptor impurity level and change the electronic band, efficiently narrowing the band gap, the Ga-doped sample shows the highest photocatalytic activity.     

Evidence of upconversion luminescence contribution to the improved photoactivity of erbium doped TiO2 systems

Er(3+)-TiO(2) synthesized by a surfactant free hydrothermal method exhibits good photoactivities under sun-like excitation for the degradation of phenol. The presence of Er(3+) does not affect the structural and morphological features of the TiO(2) significantly. The best photocatalytic performance was attained for the samples with 2 wt% of Er. Different photocatalytic runs indicated that the incorporation of the Er(3+) cation would be responsible for the enhanced photocatalytic activity, which participates in different mechanisms under UV and NIR excitation.     

Nanocrystals of CeVO4 doped by metallic heteroions

CeVO(4) nanocrystals doped by heteroions were prepared via a hydrothermal method without the presence of surfactants or templates. Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), solid state (51)V NMR, and inductively coupled plasma (ICP) were used to characterize the morphology, structure, and compositions of the materials. X-ray photoelectron spectroscopy (XPS) results confirmed that there is a valence change from Ce(3+) to Ce(4+) for a fraction of cerium atoms whereas the vanadium atoms remain in the pentavalent state V(5+) upon the substitution of Ca(2+) into CeVO(4). Raman spectroscopy was used to monitor the effects of the doping ion on the CeVO(4) lattice contraction and distortion. The appearance of the shifted and broadened Raman peaks for the doped CeVO(4) was interpreted by theoretical calculations performed with Vienna ab initio simulation package. The redox properties and photocatalytic activities of the obtained nanocrystals were also investigated and discussed in detail.