纳米结构Pt/WO3薄膜的制备、表征及氢敏性能

以钨粉和双氧水为主要原料,采用溶胶 - 凝胶法制备了WO3纳米薄膜,并用磁控溅射法在该WO3薄膜表面溅射掺杂了催化剂Pt.研究了该Pt/WO3纳米薄膜的结构和氢敏性能,结果表明,用此种方法制备的WO3基掺Pt薄膜具有良好的氢敏特性;平均膜厚160nm;薄膜经400℃以下退火处理后是非晶态结构,表面疏松多孔,氢敏效果好;经400℃以上退火处理后呈晶态结构,表面粗糙致密,氢敏效果差;Pt掺杂量对薄膜的氢敏效果有影响,掺杂量越多,氢敏效果越差.     

前驱体热处理温度对LiNi1/3Co1/3Mn1/3O2材料的影响

以NaCO3为沉淀剂,NH3·H2O为缓冲溶液,将NiSO4、CoSO4和MnSO4混合溶液共沉淀制备（Ni1/3Co1/3Mn1/3）CO3前驱体,将其在400-900℃热处理5h制备得（Ni1/3Co1/3Mn1/3）Ox氧化物。EDTA络合滴定、BET、XRD及SEM研究表明,随着热处理温度的升高,（Ni1/3Co1/3Mn1/3）Ox中过渡金属含量及结晶度随着增加,而比表面积却减小。（Ni1/3Co1/3Mn1/3）Ox与LiOH混合后在850℃热处理24h制备出LiNi1/3Co1/3Mn1/3O2材料,其结构、形貌及电性能的测试结果表明,前驱体在600℃条件下热处理制备的正极材料电化学性能最佳,其首次放电比容量为189.7mAh·g^-1,不同倍率循环60周后,循环保持率为92.4%。     

Pt／WO3纳米薄膜的氢敏特性

用溶胶-凝胶法和磁控溅射法相结合制备了催化剂Pt掺杂的WO3纳米薄膜,通过改变氢气的体积分数、催化剂Pt的含量及热处理温度等实验因素,对Pt／WO3薄膜的氢致变色性能进行了测试;并利用X射线光电子能谱仪（XPS）分析了薄膜的氢敏机理。实验结果表明：先用溶胶-凝胶法制得WO3薄膜,然后再用磁控溅射法在该WO3薄膜上溅射掺杂5％的Pt,制得Pt／WO3双层纳米薄膜,经100℃热处理后,可以获得性能稳定且具有良好氢敏特性的优质薄膜;薄膜能检测的氢气浓度低至0．008％;XPS分析表明,W^5＋与W^6＋之间的转换是引起WO3薄膜氢致变色现象的主要原因。     

Pt纳米颗粒负载SrTiO3/TiO2异质结结构制备及制氢性能

本文以固定n(Sr)/n(Ti)摩尔比0.4的SrTiO_3/TiO_2(金红石相)异质结纳米颗粒,通过"光催化还原沉积方法"制备不同质量分数的纳米铂颗粒(0、1%、2%、5%),探究其催化活性的变化,采用XRD、SEM、UV-vis、XPS方法对其进行表征,并做了相关光催化分解水产氢性能测试.结果表明:负载贵金属Pt纳米颗粒量越大,对应的Pt晶粒平均尺寸为40.8 nm,1%Pt纳米颗粒SrTiO_3/TiO_2异质结构的BET比表面积在23.195 m~2/g处最高,并且介孔材料的特征是平均Barrett-Joyner-Halenda(BJH)孔径为13.60 nm,总孔体积为0.079 cm~3/g;高BET表面积和大的总孔体积强烈地支持SrTiO_3/TiO_2具有介孔结构的事实;相应的催化剂催化活性越高,其中负载5%Pt纳米颗粒的SrTiO_3/TiO_2纳米颗粒光催化8 h产氢量为3.574 mmol,平均产氢效率为0.447 mmol/(gcat·h),但从性价比的角度来考虑,其催化效率远不及负载1%Pt纳米颗粒的SrTiO_3/TiO_2纳米颗粒催化效率的5倍,因此负载5%Pt的SrTiO_3/TiO_2纳米颗粒光催化效率最高.     

氮掺杂SrTiO3的制备及其可见光催化产氢活性研究

采用溶胶-凝胶法制备了钛酸锶,进而用固相法制备了氮掺杂SrTiO3,并用光沉积和氢气还原法制备了Pt负载的氮掺杂SrTiO3光催化剂.用XRD、SEM、UV-Vis漫反射和荧光光谱对其进行了表征和分析,考察了光催化剂在可见光下的产氢活性.研究了不同氮源、掺杂量、烧结温度和Pt负载量对催化剂产氢活性的影响.结果表明,三种不同氮源剂其掺杂效果为六次亚甲基四胺(HMT)>EDTA>尿素,而EDTA掺氮效果稍低于HMT.当氮源剂为HMT,SrTiO3与HMT质量比为1:3,焙烧温度为450℃时,所制备的光催化剂具有最佳的光催化产氢活性.在负载金属铂后,产氢活性有较大幅度的提高,其中用氢气还原法制备所得的光催化剂较光沉积法制备的具有更高的光催化活性,在最佳负载量均为2wt%时,两种光催化剂6h内的产氢量分别为6.89mmol和2.24mmol,分别是未负载铂样品产氢量的12倍和4倍多.     

Pt/Fe2O3/TiO2的制备、表征及其光催化活性研究

报道了担载不同贵金属或过渡金属氧化物的TiO2催化剂对空气中微量甲醛的光催化氧化的研究结果.实验发现,TiO2上担载Fe2O3或Pt时对甲醛均有较高的光催化氧化活性.同时担载双组分的光催化剂Pt/Fe2O3/TiO2,由于2种组分的协同作用,具有更高的光催化活性.研究了催化剂制备因素、催化剂的结构及表面特性对催化活性的影响.     

硅钛杂化介孔球负载金纳米粒子及其催化性能调控

以能源开发(如光解水制氢)及环境保护(如有机物降解)应用为目标, 负载型贵金属催化剂在设计、制备及理论研究方面已取得了长足的发展。本工作以具有特异形貌及结构的树枝状二氧化硅纳米球载体为基础, 通过溶胶-凝胶法在其孔道引入二氧化钛纳米颗粒形成硅钛杂化结构。通过有机改性技术, 在树枝状硅钛杂化纳米球表面接枝氨基官能团。然后, 通过浸渍法和硼氢化钠还原手段, 在杂化纳米球孔道负载超细金纳米粒子。不同手段表征结果显示实验成功制备了树枝状硅钛杂化纳米球负载金纳米颗粒复合材料。在模拟太阳光下, 所得催化剂光解水产氢量及速率为69.08 μmol·g^-1和13.82 μmol·g^-1·h^-1, 约为对比样催化剂(树枝状二氧化硅纳米球负载金纳米粒子)的7倍。在无光条件下, 其降解对硝基苯酚的表观动力学常数为6.540×10^-3 s^-1, 约为对比样的17倍(0.372×10^-3 s^-1)。由此可见, 设计合成的新型催化剂展现出优越的多功能催化活性。     

热处理温度对Pt—WO3薄膜结构和氢敏性能的影响

以钨粉和双氧水为主要原料,采用溶胶-凝胶法及旋转涂膜技术在K9玻璃上制备了WO3纳米薄膜,然后用磁控溅射法在该WO3薄膜表面溅射掺杂了Pt作催化剂.将此Pt-WO3薄膜分别在100～500℃的氮气环境中进行热处理,用XRD,AFM,分光光度计等观察了薄膜的结构和表面形貌,分析了薄膜的微观结构及热处理温度和催化剂含量对薄膜的结构和氢敏性能的影响.结果表明,薄膜经400℃以下热处理后是非晶态结构,表面疏松多孔,透光率较高,氢敏效果好;经400℃以上热处理后呈晶态结构,表面粗糙致密,透光率较低,氢敏效果差;催化剂Pt的含量对薄膜的氢敏效果有影响,当含量为5%(质量分数)时,Pt-WO3薄膜的氢敏感性能较好.     

Pt/TiO_2纳米薄膜的制备及光催化气相甲醇制氢的研究

通过溶胶-凝胶法制备了Pt/TiO2纳米薄膜,并在气相连续流动装置中,对甲醇的光催化脱氢反应进行了研究。将Pt/TiO2薄膜催化剂与TiO2薄膜催化剂的光催化活性进行了比较,考察了产氢量甲醇浓度、光照时间的关系,以及空速、反应温度对甲醇转化率的影响。结果表明,经过还原后分散于TiO2薄膜表面的Pt是以Pt2+及Pt0价态存在的。Pt/TiO2纳米薄膜是未负载Pt的纳米薄膜光催化活性的28倍。增加甲醇蒸汽的浓度会使产氢速率增大;当甲醇浓度在29%时,产氢速率达到最大,为4.68mmol/h。醇的转化率随着空速的增加而减小。该反应在一定的浓度范围内是一级反应,其反应的活化能为26.19kJ/mol。     

ZnO/Ag/CdCO_3纳米复合光催化剂的制备及性能研究

采用配位均匀共沉淀法制备出ZnO/Ag/CdCO3纳米复合光催化剂,用TEM、XRD、FT-IR、ICP等对产物的形貌、微观结构及组成进行了表征,着重研究了反应物配比及Cd(NO3)2浓度对ZnO/Ag/CdCO3纳米复合光催化剂催化降解甲基橙光催化活性的影响规律,结果表明,n(Zn2+):n(Ag+):n(Cd2+)=21:1.76:1.75,Cd(NO3)2浓度为0.168mol·dm-3时制得的纳米复合光催化剂对甲基橙(MO)的降解率较ZnO/Ag提高51%,ZnO/Ag/CdCO3对MO的光催化降解符合一级反应动力学方程,表观速率常数为1.4551h-1,是ZnO/Ag的7倍。     

SrTiO3-CaCr0.5Nb0.5O3 solid solutions as p-type photocatalysts for Z-scheme water splitting under visible light illumination

P-type semiconductivity has been observed in solid solution series (SrTiO3)1-x(CaCr0.5Nb0.5O3)x (0.0 ≤x ≤ 0.15),which all adopt cubic symmetry and own intense absorption in the visible light region.These solid solutions are superior H2 evolution photocatalysts under visible light illumination (λ ≥400 nm).An AQE as high as 1.02 ％ at 420 ± 20 nm has been achieved at optimal composition(SrTiO3)0.85(CaCr0.5Nb0.5O3)0.15 which significantly surpasses the parent compounds.Stoichiometric H2/O2 production under visible light illumination has been successfully realized using Z-scheme system containing (SrTiO3)0.85(CaCr0.5Nb0.5O3)0.15,WO3 and I-/IO3-redox couple.     

WO3-Ag/石墨相C3N4 Z型复合光催化剂的合成及其光催化性能

采用水热法合成WO₃纳米棒，并通过简单的溶剂蒸发法及光沉积法实现WO₃-Ag/石墨相C₃N₄(g-C₃N₄)复合光催化剂的合成。采用XRD、SEM、TEM等对材料进行全面表征。结果表明，由于成功构建了Z型异质结，WO₃-Ag/g-C₃N₄复合光催化剂能够拓展可见光响应，有效抑制光生电子与空穴复合。最佳工艺条件下所得WO₃-Ag/g-C₃N₄复合光催化剂在100 min时光催化降解罗丹明B (RhB)的效率可达96.8%，且WO₃-Ag/g-C₃N₄复合光催化剂具有优异的稳定性。光催化机制表明，光催化实验中真正的活性物质为羟基自由基与超氧自由基。      

Noble Metal-Free Reduced Graphene Oxide-Zn(x)Cd(1-x)S Nanocomposite with Enhanced Solar Photocatalytic H(2)-Production Performance

Design and preparation of efficient artificial photosynthetic systems for harvesting solar energy by production of hydrogen from water splitting is of great importance from both theoretical and practical viewpoints. ZnS-based solid solutions have been fully proved to be an efficient visible-light driven photocatalysts, however, the H(2)-production rate observed for these solid solutions is far from exciting and sometimes an expensive Pt cocatalyst is still needed in order to achieve higher quantum efficiency. Here, for the first time we report the high solar photocatalytic H(2)-production activity over the noble metal-free reduced graphene oxide (RGO)-Zn(x)Cd(1-x)S nanocomposite prepared by a facile coprecipitation-hydrothermal reduction strategy. The optimized RGO-Zn(0.8)Cd(0.2)S photocatalyst has a high H(2)-production rate of 1824 μmol h(-1) g(-1) at the RGO content of 0.25 wt % and the apparent quantum efficiency of 23.4% at 420 nm (the energy conversion efficiency is ca. 0.36% at simulated one-sun (AM 1.5G) illumination). The results exhibit significantly improved photocatalytic hydrogen production by 450% compared with that of the pristine Zn(0.8)Cd(0.2)S, and are better than that of the optimized Pt-Zn(0.8)Cd(0.2)S under the same reaction conditions, showing that the RGO-Zn(0.8)Cd(0.2)S nanocomposite represents one of the most highly active metal sulfide photocatalyts in the absence of noble metal cocatalysts. This work creates a green and simple way for using RGO as a support to enhance the photocatalytic H(2)-production activity of Zn(x)Cd(1-x)S, and also demonstrates that RGO is a promising substitute for noble metals in photocatalytic H(2)-production.     

Microwave hydrothermal synthesis of WO3(H2O)0.333/CdS nanocomposites for efficient visible-light photocatalytic hydrogen evolution

WO₃(H₂O)_0.333/CdS (WS) nanocomposites are obtained via a rapid microwave hydrothermal method, and they are served as visible light-driven photocatalysts for the H₂ generation. By using Pt as the cocatalyst, the WS nanocomposite with 70 wt.% CdS reaches the H₂ evolution rate of 10.32 mmol·g⁻¹·h⁻¹, much quicker than those of WO₃(H₂O)_0.333 and CdS. The cycling test reveals the good photocatalytic stability of the WS nanocomposite. The carrier transfer mechanism of WS nanocomposites can be explained by the Z-scheme mechanism. The existence of the Z-scheme heterojunction greatly helps to separate photogenerated carriers and thus improves the photocatalytic activity. The present work provides a rapid synthesis method for preparing Z-scheme heterojunction photocatalysts, and may be helpful for the green production of hydrogen.     

Significantly enhanced photocatalytic hydrogen production performance of g-C3N4/CNTs/CdZnS with carbon nanotubes as the electron mediators

The electron mediator can effectively improve the performance of the direct Z-scheme heterojunction photocatalysts.However,it is still a great challenge to select cheap and efficient electron mediators and to design them into the Z-scheme photocatalytic system.In the present paper,the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst was prepared using carbon nanotubes (CNTs) as the electron mediators,and its photocatalytic hydrogen production performance was studied.Compared with single-phase g-C3N4,CdZnS and biphasic g-C3 N4/CdZnS photocatalysts,the photocatalytic hydrogen production performance of the prepared g-C3N4/CNTs/CdZnS has been significantly enhanced.Meanwhile,g-C3N4/CNTs/CdZnS possesses very good photocatalytic hydrogen production stability.The enhanced photocatalytic hydrogen production performance of g-C3 N4/CNTs/CdZnS is attributed to the fact that CNTs,as an electron mediator,can accelerate the recombination of the photogenerated holes in the valence band of g-C3N4 and the photogenerated electrons in the conduction band of CdZnS,which makes the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst be easier to escape the photogenerated electrons,increases the concentration of the photogenerated carriers and prolongs the lifetime of the photogenerated carriers.This work provides a theoretical basis for the further development and design of CNTs as the intermediate electron mediator of the Z-scheme heterojunction photocatalyst.     

Intrinsic sensitivity of Cd/sub 1-x/Zn/sub x/Te semiconductors for digital radiographic imaging

The intrinsic sensitivity of cadmium zinc telluride (Cd/sub 1-x/Zn/sub x/Te) semiconductor detectors has been experimentally measured, within the X-ray diagnostic energy range. The results of this study indicate that the intrinsic efficiency of Cd/sub 1-x/Zn/sub x/Te can be increased by optimizing geometrical and physical detection parameters such as X-ray irradiation geometry, detector thickness, and applied electric field. These results indicate that Cd/sub 1-x/Zn/sub x/Te is a suitable candidate for digital imaging applications.     

Amorphous WO3-x thin films with color characteristics tuned by the oxygen vacancies created during reactive DC sputtering

Tungsten oxides are interesting for a variety of applications due to their versatile optoelectronic charac-teristics,which can be tuned changing the composition and/or the crystalline structure.Coloration due to sub-bandgap absorption is often achieved by ion intercalation or doping in WO3:M films(with M=H+,Li+,Na+,etc.introducing extra electrons),but a more direct way is creating charged oxygen vacancies(Vo+and/or Vo2+)in sub-stoichiometric WO3-x forms.Here,amorphous WO3-x thin films are obtained by reactive DC sputtering of a pure W target,on unheated glass substrates,changing the oxygen to argon pressures ratio.The control of intrinsic defects(oxygen vacancies and tungsten valence states)by the oxy-gen partial pressure allows tuning the morphology,sub-bandgap absorption and carrier density in these WO3-x films,as it is proven by Raman spectroscopy,atomic force microscopy,optical spectrophotometry and Hall effect measurements.     

Cd/sub 1-x/Mn/sub x/Te semimagnetic semiconductors for ultrafast spintronics and magnetooptics

We present ultrafast optical characterization of Cd/sub 1-x/Mn/sub x/Te single crystals with high (x>0.5-Mn) concentration, studied by magnetooptical sampling and time-resolved magnetization modulation spectroscopy. We have demonstrated that the dynamics of both Mn spins and carrier spins in Cd/sub 1-x/Mn/sub x/Te is extremely fast (in the subpicosecond range), making the nanostructures based on this material very promising for applications in spintronics and magnetooptics.     

Facile synthesis of defected TiO2-x (B) nanosheet/graphene oxide hybrids with high photocatalytic activity

TiO2 (B) nanosheets/GO (graphene oxide) hybrids are considered to be outstanding performance pho-tocatalysts for high efficiency of H2 evolution.However,they still suffer severe challenges during the synthetic processes,such as a large amount of the capping agents adhering on the surface and easy occurrence of aggregation.To figure out these obstacles,Ar plasma treatment as a modified method in this study not only enable the TiO2 (B) nanosheets distributed uniformly on the GO sheets but also engi-neer defects within TiO2 (B) nanosheetsto significantly improve the photocatalytic activity for the water splitting.The hydrogen evolution rate of the TiO2-x (B)/GO sheets is 1.4 times higher compared with that of original TiO2 (B)/GO sheets without Ar plasma treatment.The improved photocatalytic proper-ties were owing to the synergetic effects of oxygen vacancies and the heterojunction between GO and TiO2 (B),which can promote the visible light utilization and accelerate separation and transportation of photogenerated electron-holes.This study can provide a facile pathway to prepare the two-dimensional hybrid photocatalysts with high photocatalytic H2 activity.     

Experimental and DFT Studies of Au Deposition Over WO3/g-C3N4 Z-Scheme Heterojunction

A typical Z-scheme system is composed of two photocatalysts which generate two sets of charge carriers and split water into H2 and O2 at different locations.Scientists are struggling to enhance the efficiencies of these systems by maximizing their light absorption,engineering more stable redox couples,and discovering new O2 and H2 evolutions co-catalysts.In this work,Au decorated WO3/g-C3N4 Z-scheme nanocomposites are fabricated via wet-chemical and photo-deposition methods.The nanocomposites are utilized in photocatalysis for H2 production and 2,4-dichlorophenol(2,4-DCP)degradation.It is investigated that the optimized 4Au/6%WO3/CN nanocomposite is highly efficient for production of 69.9 and 307.3μmol h−1 g−1 H2 gas,respectively,under visible-light(λ>420 nm)and UV–visible illumination.Further,the fabricated 4Au/6%WO3/CN nanocomposite is significant(i.e.,100%degradation in 2 h)for 2,4-DCP degradation under visible light and highly stable in photocatalysis.A significant 4.17%quantum efficiency is recorded for H2 production at wavelength 420 nm.This enhanced performance is attributed to the improved charge separation and the surface plasmon resonance effect of Au nanoparticles.Solid-state density functional theory simulations are performed to countercheck and validate our experimental data.Positive surface formation energy,high charge transfer,and strong non-bonding interaction via electrostatic forces confirm the stability of 4Au/6%WO3/CN interface.