Selective oxidation of CO in the presence of air over gold-based catalysts Au/TiO2/C (sonochemistry) and Au/TiO2/C (microwave)

Two model catalysts, Au/TiO2/C (S) (sonochemically derived) and Au/TiO2/C (M) (microwave derived), were produced by employing ultrasound irradiation and microwave irradiation, respectively. The deposition of gold colloids onto the support powders, TiO2/C, was accomplished by using a solvated metal atom impregnation (SMAI) method. The SMAI technique provides highly-dispersed gold particles on the TiO2/C support. The catalytic performance of Au based catalysts 1 wt% Au-TiO2/C (S) and 1 wt%Au-TiO2(M)/C (M) have been tested for the oxidation of CO in the temperature range of 0-300 degrees C and compared to that of 1 wt% Au-TiO2 (Degussa-P25). A boost in the conversion of CO was observed for the sonochemically-derived catalyst, Au/TiO2/C (S), at low temperature. Hence, the reactivity order found for CO oxidation is (Au/TiO2/C (S)>Au/TiO2 (P25)>Au/TiO2/C (M)).     

Application of TiO2 with different structures in solar cells

The application of TiO2-based devices is mainly dependent on their crystalline structure,morphology,size,and exposed facets.Two kinds of TiO2 with different structures,namely TiO2 pompons and TiO2 nanotubes,have been prepared by the hydrothermal method.TiO2 with different structures is characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),and Brunauer-Emmett-Teller(BET) surface area analysis.Solar cells based on poly(3-hexylthiophene)(P3HT) and TiO2 with different structures are fabricated.In the device ITO/TiO2/P3HT/Au,the P3HT is designed to act as the electron donor,and TiO2 pompons and TiO2 nanotubes act as the electron acceptor.The effects of the TiO2 structure on the performance of hybrid heterojunction solar cells are investigated.The device with TiO2 pompons has an open circuit voltage(Voc) of 0.51 V,a short circuit current(Jsc) of 0.21 mA/cm2,and a fill factor(FF) of 28.3%.Another device with TiO2 nanotubes has a V oc of 0.5 V,J sc of 0.27mA/cm2,and FF of 28.4%.The results indicate that the TiO2 nanotubes with a unidimensional structure have better carrier transport and light absorption properties than TiO 2 pompons.Consequently,the solar cell based on TiO2 nanotubes has a better performance.     

锐钛矿型氧化物XO2（X=Ti,Sn,Zr,Ir）表面氧化性对NH3气体光学气敏传感特性的影响

摘要 金属氧化物气敏传感材料一直是当今的热门研究课题,锐钛矿相金属氧化物XO2（X=Ti,Sn,Zr,Ir）是具有传感特性的常见材料。光学气敏效应是指气体分子吸附在气敏传感材料上,与表面氧空位发生氧化还原反应,由于光学性质发生改变而检测出气体的成分和浓度,因此,氧化还原反应的强弱是反应传感性能的核心原因。本文采用密度泛函理论(DFT)体系下广义梯度近似(GGA)第一性原理平面波超软赝势方法,分析和计算了含氧空位的锐钛矿相XO2（X=Ti,Sn,Zr,Ir）表面特性。通过以NH3为目标分子,研究分子表面吸附引起的氧化还原反应的机理,分析不相同的氧化物表面的几何结构、吸附能、态密度、差分电荷密度、电荷布居、电荷转移、光学性质等。研究发现：目标分子稳定吸附在氧化物表面后改变材料光学性质。SnO2表面对分子的吸附能最大,IrO2表面与分子的吸附距离最小。NH3分子与表面间存在电荷转移,其转移电子数目大小为:IrO2＞TiO2＞ZrO2＞SnO2,氧化物表面氧化性的大小为:IrO2氧空位＞TiO2氧空位＞ZrO2氧空位＞SnO2氧空位;比较吸收谱和反射谱发生变化最为明显的是TiO2表面。结论,在可见光范围内,波长在400~530nm时,SnO2表面光学气敏传感效应更好。而在530~760nm范围TiO2表面光学气敏传感效应更好。     

Bonding of gold nanoclusters to oxygen vacancies on rutile TiO2(110)

Through an interplay between scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we show that bridging oxygen vacancies are the active nucleation sites for Au clusters on the rutile TiO2(110) surface. We find that a direct correlation exists between a decrease in density of vacancies and the amount of Au deposited. From the DFT calculations we find that the oxygen vacancy is indeed the strongest Au binding site. We show both experimentally and theoretically that a single oxygen vacancy can bind 3 Au atoms on average. In view of the presented results, a new growth model for the TiO2(110) system involving vacancy-cluster complex diffusion is presented.     

时间分辨红外光谱研究Pt/TiO2上甲醇光催化反应中光生电子衰减动力学

采用时间分辨红外光谱直接观测了甲醇在Pt/TiO2上光催化反应制氢过程中光生电子还原氢离子生成氢气的反应过程．结果表明Pt的担载量存在一最佳值，使得该催化剂中光生电子的反应速度最快．当Pt担载量相同时，Pt/TiO2催化剂中光生电子参与产氢反应的速度随样品还原温度的不同而明显变化．可能的原因是较高温度下氢气还原的Pt/TiO2催化剂中Pt粒子占据了TiO2表面的一些能够解离吸附甲醇的活性位置，而对于较低温度下氢气还原的Pt/TiO2催化剂，这种占据作用很不明显．实验中还发现瞬态动力学研究中光生电子衰减较快     

掺磷TiO_2优化TiO_2/MBA/Ag三明治结构的SERS性能

本文以磷酸为磷源,通过溶胶水热法制备磷掺杂TiO_2,利用Lee和Meisel的方法制备银溶胶,以4-巯基苯甲酸(MBA)为探针分子,通过构建TiO_2/MBA/Ag三明治结构,研究磷掺杂二氧化钛对该基底表面增强拉曼(SERS)性能的提升。通过TEM、XRD、XPS、DRS和拉曼光谱图表征二氧化钛的形貌结构、化学组成、光学和拉曼性能,结果表明,制备出的磷掺杂二氧化钛为锐钛矿型纳米颗粒,粒径范围6~12nm,XPS显示磷以P~(5+)替代了Ti~(4+),形成O-P-O键掺入TiO_2的晶格中,当磷的掺杂量在1.77%时,TiO_2/MBA/Ag三明治体系具有最佳的SERS信号,这是因为适量的磷掺杂降低了TiO_2的能带间隙,丰富TiO_2的表面态,这能促进TiO_2向MBA分子的电荷转移。     

亚纳米厚的氧化铝包裹层可以显著提高负载型金纳米颗粒催化剂的热稳定性

负载型金纳米颗粒催化剂在许多催化反应中展现出非常好的催化活性,但是金纳米颗粒在高温等反应条件下容易烧结团聚,极大地限制了金催化剂的应用。利用原子层沉积技术在Au/TiO₂催化剂表面分别精确沉积了一层超薄的二氧化钛和氧化铝包裹层,并对比研究了包裹层对金纳米颗粒的热稳定性影响。原位红外漫反射CO吸附和x-射线光电子能谱数据证实了氧化物包裹层的存在。发现亚纳米厚的氧化铝包裹层能够在600 C完全避免金纳米颗粒的团聚;相反,二氧化钛包裹层对金纳米颗粒稳定性的提高没有明显效果。通过CO氧化探针反应的活性测试,发现随着煅烧温度的升高氧化铝包裹的Au/TiO₂ 催化剂的活性逐渐提高,表明高温处理可以促进被包裹金原子的暴露并表现出催化活性。提供了提高金纳米颗粒稳定性的有效方法,为拓展金催化剂在条件苛刻的反应中的应用奠定了技术基础.     

Influence of Au and TiO2 structures on hydrogen dissociation over TiO2/Au(100)

We performed H₂–D₂ exchange reactions over TiO_x/Au(100) and compared the observed reaction kinetics with those reported for TiO_x/Au(111) in order to clarify the influence of the Au and TiO₂ structures on dissociation of H₂ molecules. Low energy electron diffraction observations showed that the TiO₂ produced on Au(100) was disordered, in contrast to the comparatively ordered TiO₂ structure formed on Au(111). The activation energies and the turnover frequencies for HD formation over TiO₂/Au(100) agreed well with those for TiO₂/Au(111), clearly indicating that the hydrogen dissociation sites created over TiO₂/Au(100) were the perimeter interface between stoichiometric TiO₂ and Au, as was previously concluded for TiO₂/Au(111). We concluded that the creation of active sites for hydrogen dissociation was independent of the Au and TiO₂ structures consisting perimeter interface, and that local bonds that formed between Au and O atoms of stoichiometric TiO₂ were essential for the creation of active sites.     

基于FTIR与UV-Vis的Ce-La/TiO_2光-湿-热复合材料制备机理

为获得具有调温调湿且能够进行光催化降解有害物质的多功能复合材料,利用溶胶-凝胶法制备Ce-La/TiO_2空心微球,以Ce-La/TiO_2空心微球为载体材料,采用真空吸附法将相变材料——癸酸-棕榈酸填充在Ce-La/TiO_2空心微球的空腔中制备具有光-湿-热协同性能的Ce-La/TiO_2复合材料。采用傅里叶红外光谱仪(FTIR)对制备过程中主要阶段的产物进行测试,研究SiO2模板的构建作用,表面活性剂聚乙烯吡咯烷酮(PVP)的衔接作用,癸酸-棕榈酸的嵌入对Ce-La/TiO_2空心微球的影响,利用紫外-可见分光光谱仪(UV-Vis)对Ce-La/TiO_2复合材料的光响应范围进行测试,研究Ce-La共掺杂对TiO_2空心微球光响应能力的影响,采用扫描电镜(SEM)对Ce-La/TiO_2复合材料的微观形貌进行表征分析,进一步阐明Ce-La/TiO_2复合材料制备机理。结果表明,氨水提供的碱环境有利于正硅酸乙酯缩合反应,在780.00cm-1处生成Si—O—Si基团,搭建SiO2网络骨架,形成内核,作为支撑TiO_2壁材的模板,构建TiO_2的空腔结构;表面活性剂PVP的添加,在1 035.00cm-1处形成—C—N—基团,有利于TiO_2附着在SiO2的表面;高温煅烧能够有效去除PVP避免杂质离子引入到Ce-La/TiO_2复合材料体系中。Ce-La共掺杂使Ce-La/TiO_2复合材料的吸收边带发生红移,提高在可见光下的催化降解能力,同时在1 630.00cm-1处出现—OH基团能够提高CeLa/TiO_2复合材料的亲水性。癸酸-棕榈酸较好的填充于Ce-La/TiO_2空心微球的空腔中,各组分的特征吸收峰没有发生明显变化,能够保持各组分的基本性能不变。     

TiO2/SiO2的表面化学修饰及其DRS和Raman光谱分析

以氯化醇钛盐表面反应法制备系列TiO2/SiO2,根据XRD,Raman和DRS表征分析,载体表面具有分子级分散的锐钛矿型TiO2微晶粒子和非晶TiOx物种.与本体TiO2相比,TiO2/SiO2的吸收带边显著蓝移,能隙增大为3.96 eV.当金属M(M:Pd,Cu和Ni)负载于TiO2/SiO2表面,可使其光吸收域扩展到可见光区,并引起吸收带边红移.相对Pd的负载,Cu,Ni的负载对TiO2/SiO2的LMCT带影响更大,其中Cu-TiO2/SiO2的能隙减小为3.68 eV.当金属氧化物MoO3负载于TiO2/SiO2上时,可以调变TiO2/SiO2的吸收带边并增强对可见光的吸收;随MoO3载量的增加,表面物种的相互作用增强,形成Mo-O-Ti复合结构,增强了LMCT带的吸收强度,并使能隙减小为3.81 eV.     

基于金纳米棒@二氧化硅表面等离子体共振增强的有机太阳能电池

把包裹SiO₂的金纳米棒（Au NRs@SiO₂）掺杂到有机太阳能电池的活性层中,利用表面等离子体共振效应来增强活性层对光的吸收,从而提高有机太阳能电池的能量转换效率。研究了不同掺杂浓度和不同包裹厚度对电池性能的影响。结果表明,掺杂浓度为1.5%时,器件性能最佳,能量转换效率达到4.02%;SiO₂壳层厚度为3 nm时,转换效率达到4.38%,较标准电池提升了29.2%。     

双金属/TiO2纳米管复合结构中增强的光电流

将传统半导体材料与金属微纳结构相结合,利用其表面等离激元共振效应,可有效地增强复合结构的光电转换效率,使其广泛地被用于光电化学和光电探测等领域.本文以氧化铝纳米管为模板,采用原子层沉积技术制备出高有序的TiO2纳米管,并通过电子束热蒸发技术在大孔径的纳米管薄膜中分别负载金、铝和双金属金/铝纳米颗粒,形成金属纳米颗粒/TiO2纳米管复合结构.研究结果表明,相对于纯TiO2纳米管,Au/TiO2复合纳米管在568 nm的可见光照射下,其光电流密度约有400%的提高;在365 nm紫外光照射下,Al/TiO2复合纳米管的光电流提高约50%;同时负载双金属Au和Al纳米颗粒的TiO2纳米管在整个紫外-可见光区域光电流均显著增强.     

C1催化剂MoS2/K2CO3/TiO2的制备

根据“盐类及氧化物等在高比表面载体上有自发分散倾向”的原理，制备了一种新型的用于由合成气（H2／CO）合成甲醇的催化剂MoS2/K2CO3/TiO2(DSA),该催化剂具有较好的耐硫性和对甲醇有较高的选择性。     

XPS analysis of β-AlF3 phases with Al successively substituted by Mg to be used for heterogeneously catalyzed Cl/F exchange reactions

A new method of static charge referencing was applied in a XPS study of β-AlF₃ phases with aluminum successively substituted by magnesium. This class of compounds is characterized by strong Lewis acid sites, which are assumed to be the catalytically active sites for Cl/F exchange reactions. In order to adjust their strengths Mg was introduced into the β-AlF₃ lattice. At low amounts of Mg the resulting samples were found to be highly catalytically active in Cl/F exchange reactions. 20 nm gold particles were deposited on the sample surface to provide a static charge reference. With the help of this procedure binding energies (BE) of photo peaks as well as kinetic energies (KE) of Auger electron emission peaks are presented in relation to the Au4f_7/2 BE reference. Furthermore, a detailed analysis of the relaxation behavior of the Mg nucleus lead to the conclusion that, at low Mg contents, strong Lewis acidic Mg cations in Mg_xF_y clusters act as the catalytically active sites. At high Mg contents, small MgF₂ like crystallites are formed in the disturbed β-AlF₃ lattice, which are catalytically inactive as MgF₂.     

RuO2/TiO2/漂珠复合光催化剂的制备及性能

"利用RuO2/TiO2前驱体溶胶,采用溶胶-凝胶-浸渍法在漂珠(FP)表面沉积RuO2/TiO2膜,经120 ℃干燥、500 ℃焙烧制备复合光催化剂RuO2/TiO2/FP,并通过SEM、XRD以及FT-IR分别对其结构进行了表征． 结果表明,RuO2/TiO2膜的平均厚度(三层)约1 1m,膜材料中TiO2主要呈现锐钛矿型结构,而RuO2是以非晶态高度分散在粒子表面．以高效氯氰菊酯杀虫剂的光催化降解为模型反应,研究了RuO2/TiO2/FP的光催化性能,探讨了影响催化剂活性的因素及采用太阳光做光源处理     

Effect of TiO2 powder addition on sonochemical destruction of 1,4-dioxane in aqueous systems

Effects of TiO(2) powder addition on sonochemical destruction of 1,4-dioxane in water were investigated through comparison of a SiO(2) powder that had similar specific surface area. Results show that addition of TiO(2) is more effective for decomposition of 1,4-dioxane in water than addition of SiO(2). The contribution of photocatalytic destruction through sonoluminescence is not a dominant mechanism for acceleration of sonochemical reactions by adding TiO(2). Sonication of TiO(2)-added water generated thermally excited holes in this case. Moreover, intrinsic oxygen vacancies in TiO(2) surface play an important role in achieving high decomposition efficiency by producing cavitation. The addition of reduced TiO(2) powder increases both the ultrasonication energy that is consumed in water and the destruction efficiency of 1,4-dioxane.     

空气电极/AC作载体对TiO2光催化性能的影响

研究了空气电极和活性碳 (AC)作载体对TiO2 光催化氧化活性艳红 (K 2BP)性能的影响 .实验结果表明 ,用空气电极 /AC作载体能显著提高TiO2 的光催化反应速度 ;空气电极不仅具有良好的合成H2 O2 的性能 ,而且对TiO2 光催化剂可产生大约 +0 .5V的偏压作用 ,大大减小了TiO2 光生电荷的复合几率 ;AC对有机物分子良好的吸附作用提高了有机物分子在TiO2 表面及周围的富集浓度 ,其含量在 2 1%左右可使光催化剂达到最佳的催化效果 .复合电极工作电流密度对活性艳红的氧化脱色速度有影响 ,i=15mA/cm2 ,速度达到最大 ;活性艳红分子在复合电极表面的吸附受溶液pH值的影响 ;提出了复合电极的工作原理 .     

Multienzyme-Mimetic Activity of Gold/Cerium Oxide Nanozyme

Redox-active nanozymes offer low-cost controlled synthesis, high stability, and tunable catalytic properties over natural enzymes, which have attracted wide attention in the field of disease diagnosis and treatment. However, the improvement of catalytic activity remains an important challenge for nanozymes. Herein, the Au/CeO₂ nanozymes is developed to achieve enhanced multiple enzyme-mimetic activity. The Au/CeO₂ nanozymes at 5% doping possess best peroxidase-like activity with threefold higher catalytic rate than CeO₂. For catalase-mimic catalysis, the Au/CeO₂ nanozymes at 5% doping also exhibited a 1.5-fold enhanced reaction rate higher than pure CeO₂. The superoxide dismutase (SOD)-like capacity of Au/CeO₂ nanozymes is proportional to Au content. The Au/CeO₂ nanozymes at 10% doping show optimal SOD-like capacity of 60.2 U mg⁻¹. In vitro experiments validate the regulation ability of intracellular oxidative stress and inflammation. Au/CeO₂ nanozymes can reduce lipopolysaccharide- or H₂O₂-induced oxidative damage by scavenging excess ROS in nerve cell. Therefore, Au/CeO₂ can be used as a promising antioxidant in disease treatment, and the study offers general guidelines for achieving enhanced biocatalytic property through atomic doping.     

Twisted Hubbard model for Sr2IrO4: magnetism and possible high temperature superconductivity

Sr(2)IrO(4) has been suggested as a Mott insulator from a single J(eff)=1/2 band, similar to the cuprates. However, this picture is complicated by the measured large magnetic anisotropy and ferromagnetism. Based on a careful mapping to the J(eff)=1/2 (pseudospin-1/2) space, we propose that the low energy electronic structure of Sr(2)IrO(4) can indeed be described by a SU(2) invariant pseudospin-1/2 Hubbard model very similar to that of the cuprates, but with a twisted coupling to an external magnetic field (a g tensor with a staggered antisymmetric component). This perspective naturally explains the magnetic properties of Sr(2)IrO(4). We also derive several simple facts based on this mapping and the known results about the Hubbard model and the cuprates, which may be tested in future experiments on Sr(2)IrO(4). In particular, we propose that (electron-)doping Sr(2)IrO(4) can potentially realize high-temperature superconductivity.     

Enhanced light absorption of TiO(2) in the near-ultraviolet band by Au nanoparticles

We propose a scheme to enhance near-UV band absorption of a rutile TiO(2) nanoparticle by placing Au nanoparticles in its neighborhood. The discrete-dipole approximation method was employed to calculate the absorption spectrum of pure rutile TiO(2) and that of TiO(2) mixed with Au nanoparticles. The results indicate that pure rutile TiO(2) has its maximum absorption located in the deep-UV band. With the existence of Au nanoparticles, a significant light harvesting effect occurs, and this maximum shifts to the near-UV band, where usual excitation wavelength falls.