Promoting Effects of Iron on CO Oxidation over Au/TiO2 Supported Au Nanoparticles

Fe-doped TiO₂ supported gold nanoparticles as high-performance CO oxidation catalysts were prepared. XRD data revealed that TiO₂ support was in an anatase phase. After calcination at 300℃, the sample showed nanotube structure, and the size of gold nanoparticles was 3.1 nm. When calcined at 500℃, most nanotubes broke, and gold nanoparticles grew up to 5.9 nm. XPS spectrum indicated the presence of Fe in the +3 oxidation state. Au/Fe-TiO₂(Au:1.44%, Fe:1.35%) calcined at 300℃ possessed the best catalytic activity, and it could completely convert CO at 25℃. The temperature of 100% CO conversion(T_100%) of Fe-free catalyst was 40℃. After the catalysts were stored at room temperature for 7 d, T_100% of Au/Fe-TiO₂ increased from 25℃ to 30℃, while T_100% of Fe-free catalyst increased from 40℃ to 80℃. The catalytic activity and storage stability of Au/TiO₂ could be improved by Fe-doping. The increase of specific surface area, generation of oxygen vacancies and new adsorption sites, depression of the growth of gold nanoparticles, and strong metal-support interaction were responsible for the promoting effect of iron on the catalytic performance of Au/TiO₂ for CO oxidation.     

多种纳米结构Fe掺杂TiO2光热耦合水分解制氢研究

氧空位是材料缺陷工程的重要组成. 基于光生氧空位的直接热利用, 实现纯水分解制氢的光热耦合实验, 被认为是太阳能综合利用的有效途径. 以多种制备方法合成的TiO₂纳米材料为基础, 研究了多种形貌纳米TiO₂及其Fe掺杂改性材料的光热耦合反应能力. 通过高分辨透射电子显微镜(HRTEM)、 X射线衍射(XRD)和电子顺磁共振(EPR)对晶体特征进行表征, 利用漫反射光谱(DRS)、 光致发光(PL)和三电极测试法表征了材料的性能, 并结合密度泛函理论(DFT)计算了产氢反应路径. 研究结果表明, 溶胶-凝胶法制备的纳米颗粒相比水热法制备的纳米片及纳米线, 体相内缺陷较多, 载流子强度高, 光热耦合产氢效果较差. Fe掺杂改性扩展了光响应, 增强了载流子分离和寿命, 降低了电子传输阻抗, 利于光反应过程中光生氧空位的形成, 克服了制氢反应中的关键能垒. 同时, 纳米材料中的缺陷促进了Fe离子的有效掺杂, Fe掺杂TiO₂纳米颗粒的光热耦合平均产氢量为9.73 μmol/g, 性能提升达13倍.     

偏压控制Cu2O和Cu在TiO2表面的生长及其光电化学性质

基于TiO2/Ti电极在含Cu2+溶液中的循环伏安图,调节电沉积的沉积电压,我们在TiO2平整表面制备出Cu2O和/或Cu颗粒.通过扫描电镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)表征,发现Cu2O和Cu有不同的生长机制:Cu2O颗粒在TiO2表面分散结晶,而Cu颗粒是在已生长的颗粒上成核,从而形成堆积颗粒结构.这是由于在Cu2O/TiO2界面和Cu/TiO2界面形成不同的能带结构,使得电子的转移方式不同.与纯TiO2光阳极比较,可以观察到Cu2O/TiO2和Cu/TiO2异质结构的光电流均有显著增强.特别地,存在一个电压区间使得Cu2O和Cu同时生长在TiO2表面,此时对应的光电流比较稳定并且能达到最大.紫外-可见(UV-Vis)漫反射光谱、电化学阻抗谱(EIS)和光电流-电压特性曲线均显示,Cu2O和Cu明显有助于光的可见光吸收,同时Cu/TiO2在光电转换过程中显示更宽波段的可见光利用率.此外,开路电压的增加、有效的电荷分离和电极/电解质界面上载流子的快速迁移也增强了材料的光电化学性质.     

一步火焰辅助热解法制备Fe掺杂嵌碳TiO2及其光催化性能

以钛酸四丁酯、无水乙醇和无水氯化铁为前驱体,通过一步火焰辅助热解法制备了Fe掺杂嵌碳TiO₂,并研究了样品的光催化活性. 利用扫描电子显微镜及能谱、X射线光电子能谱、X射线粉末衍射和紫外-可见漫反射吸收光谱等对样品的形貌、组分、晶型和光吸收进行了表征,并研究了样品在紫外和可见光下的光催化活性. 结果表明,无需后续热处理可直接得到主要是锐钛矿相TiO₂的样品,Fe³⁺以替位掺杂形式进入TiO₂晶格,随掺杂量增加,样品在可见光区域的吸光度提高,吸收带边红移. Fe掺杂量（摩尔分数）小于0.2%可改善样品的光催化活性,当Fe掺杂量为0.1%时,样品在可见光和紫外-可见光照射下均显示出最高的降解亚甲基蓝速率.     

Preparation and photoelectrochemical characterization of nano-particulate TiO2 and polyaniline composite films on Au

TiO₂ and polyaniline(PANI) composite film was obtained by electrochemical methods^[1] and investigated for solar energy conversion application. A strong rectifying effect was found in the cyclic voltammogram of the film in dark when the scan speed was slow enough (5 mV/s) and a quasi-reversible voltammogram of the film was observed when the scan speed was fast (100 mV/s). The results of both the cyclic voltammograms and the SEM images of the composite film show that the PANI film is almost completely covered with nano-particulate TiO₂. Two anodic photocurrent bands and a cathodic band was observed in the spectra of the photocurrent of the TiO₂/PANI/PATP(p-aminothiophenol)/Au film in 0.05 mol/L Fe(CN)₆^3-/Fe(CN)₆^4- solution. The band at 300~400 nm (3.1~4.1 eV) can be ascribed to the photocurrent band of TiO₂ particles and the bands at 450~730 nm (1.7~2.8 eV) can be ascribed to those of the PANI. The partially-oxidized PANI has internal photoemission function and the insulating matrix of PANI is verified to be reduced PANI with a 3.33 eV bandgap energy. The flat-band potentials of partially-oxidized PANI and TiO₂/PANI composite film in 1.0 mol/LHClO₄ solution are determined as 0.87 V and 0.09(SHE) from Mott-Schottky plots, respectively.     

Si掺杂TiO2催化剂的结构与可见光催化活性研究

采用溶胶-凝胶法制备出Si⁴⁺离子掺杂的TiO₂可见光催化剂 (TiO₂-xSi),该催化剂的可见光催化活性高于纯TiO₂和N掺杂的TiO₂(TiO₂-N).利用XRD、XPS、FT-IR和UV-Vis DRS等表征技术,研究了TiO₂-xSi催化剂的晶体结构、能带结构和表面性质.研究发现:掺入Si⁴⁺离子在TiO₂粒子表面主要形成Ti-O-Si结构,并在导带下0.2-0.6 eV区域形成表面态能级,该表面态能级的存在是催化剂产生可见光响应、实现可见光催化的根本原因.另外,讨论了Si⁴⁺离子的掺杂对金红石相和晶粒的生长抑制作用,以及催化剂的比表面积和表面羟基物种增加对可见光催化活性的影响.     

磁功能性TiO2光催化剂的制备及特性

采用溶胶-凝胶法以Fe₃O₄为磁核制备了磁功能性光催化剂,以甲基橙为模拟污染物,考察了掺杂Fe比例、催化剂煅烧温度以及煅烧时间对催化剂活性的影响.催化剂的最佳制备条件为:Fe₃O₄掺杂Fe含量为5%,煅烧温度为450 ℃,煅烧时间为2 h.通过TG-DTA、XRD、UV-Vis、TEM对催化剂进行了表征,结果表明:制备的催化剂具有明显的核壳结构,原Fe₃O₄磁核经过高温煅烧被氧化;TiO₂包覆在磁核表面;催化剂的吸收带边发生红移,在可见光区的吸收强度有所增强;催化剂颗粒的平均粒径为20 nm.     

ZnSe/MoO_3/TiO_2复合膜的制备及其光生阴极保护效应

针对TiO_2半导体不能有效吸收可见光,光电转换效率较低等问题,可通过对TiO_2半导体进行修饰和改性,制备TiO_2复合材料,提高其光电化学性能。因此,本工作以Ti表面制备的TiO_2纳米管膜为基础,分别应用循环伏安电沉积法和脉冲电沉积法在膜表面先后沉积MoO3和ZnSe颗粒,获得具有级联能带结构的ZnSe/MoO3/TiO_2纳米管复合膜,并将其应用于对403不锈钢(403SS)实施光生阴极保护。相较于纯TiO_2纳米管膜,紫外-可见(UV-Vis)吸收光谱和光致发光(PL)谱测试表明,ZnSe/MoO3/TiO_2复合膜的吸收边红移,在可见光区具有良好的光吸收性能,光生载流子复合得到更有效抑制。光电化学测试表明,白光照射下,处于0.5 mol·L~(-1) KOH溶液中的ZnSe/MoO3/TiO_2复合膜的光电流密度达到了同条件下纯TiO_2膜的2倍,可使与之耦连的浸泡于0.5 mol·L-1 NaCl溶液中的403SS电极电位下降470 mV,显示出良好的光生阴极保护效应。复合膜还具有一定的储能特性,在光照后又转为暗态的22.5 h内仍对403SS具有一定阴极保护作用。     

异质结型光催化膜的活性及其机理研究

采用浸渍提拉法制得TiO₂,ZnO,Fe₂O₃,ZnO/TiO₂,TiO₂/ZnO,Fe₂O₃/TiO₂和TiO₂/Fe₂O₃石英玻璃基底负载膜.光催化降解亚甲基蓝实验表明,TiO₂和ZnO具有良好的光催化活性,Fe₂O₃活性较差.但形成异质结后,TiO₂和Fe₂O₃的光催化降解能力发生明显的变化.用254nm紫外光光照后,TiO₂,ZnO和Fe₂O₃等3种氧化物膜与水的接触角均有不同程度的降低,TiO₂表现出超亲水性,ZnO/TiO₂和Fe₂O₃/TiO₂膜与水的接触角小于对应的单纯ZnO和Fe₂O₃膜与水的接触角,其中Fe₂O₃/TiO₂表面出现超亲水性.瞬态光电导谱的少数载流子寿命的测定表明,异质结势垒电场能有效地增强光生电子-空穴对的分离效率.根据能带理论建立的两组异质结能带模型可合理地解释实验结果.     

Dispersion properties of TiO2 nano-powder synthesized by homogeneous precipitation process at low temperatures

The dispersion stability of rutile TiO₂ powder with a unique nano-structure synthesized by homogeneous precipitation process at low temperatures (HPPLT) has been investigated with adding the various electrolytes in both pure aqueous and organic media. Zeta potential measurements have shown that the addition of electrolytes such as CsCl, CaCl₂, FeCl₃, and ZrCl₄ to aqueous and pure organic dispersion media leads to generally a charge reversal from negative to positive on the surface of TiO₂ particle. The electrostatic repulsive force acting on between TiO₂ particles dispersed in pure organic media was found to be significantly greater than that in aqueous media, which is closely related to the physical properties of the organic solvents, such as viscosities and dielectric constant. The surface potentials of TiO₂ particles have been greatly modified by the particulate properties, pH, dispersion medium, and valence of the ionic species, which governs the colloidal behavior of TiO₂ particles virtually.     

Sn4+掺杂对TiO2纳米颗粒膜光催化降解苯酚活性的影响

金属离子掺杂能改善TiO2纳米微粒光催化活性,在光降解大气和水污染物的研究中,已引起人们的重视[1,2].实验证明,掺杂物的浓度、掺杂离子的分布、掺杂能级与TiO2能带匹配程度、掺杂离子d电子的组态、电荷的转移和复合等因素对催化剂的光催化活性有直接影响[3].Kamat等[4]曾利用TiO2颗粒与SnO2颗粒混合制膜,使光催化剂活性得到提高.但Sn4+掺杂TiO2用于光催化剂尚少见报道.本文采用等离子体化学气相沉积法(PECVD)[5]制备了Sn4+离子掺杂的TiO2纳米颗粒膜催化剂(TiO2-Sn),考察了其对苯酚的光催化降解活性,讨论了Sn4+离子的掺杂方式及光催化活性提高的机理.     

Synthesis of N-TiO2@NH2-MIL-88(Fe) Core-shell Structure for Efficient Fenton Effect Assisted Methylene Blue Degradation Under Visible Light

Core-shell TiO₂-based photocatalysts with specific composition, morphology, and functionality have attracted considerable attention for their excellent degradation properties on organic pollutants via a photocatalytic oxidation process. Herein, a N-TiO₂@NH₂-MIL-88(Fe) core-shell structure was prepared by coating NH₂-MIL-88(Fe) on nitrogen-doped TiO₂(N-TiO₂) nanoparticles. Introduction of heteroatom nitrogen to pure TiO₂ expands the spectral response range, leading to enhanced quantum efficiency of photocatalyst. Furthermore, loading NH₂-MIL-88(Fe) on N-TiO₂ improved the adsorption ability of the nanocomposites due to the porous tunnels of NH₂-MIL-88(Fe). The resulted core-shell N-TiO₂@NH₂-MIL-88(Fe) nanocomposites realized the transfer of photo excited electrons from N-TiO₂ to NH₂-MIL-88(Fe) rapidly, partially reduced Fe³⁺ to Fe²⁺ in NH₂-MIL-88(Fe), and further enhanced the Fenton effect on efficiently degrading methylene blue dye(MB) under visible light(λ ≥ 420 nm) with the assistance of H₂O₂.     

氟钒锰共掺对TiO2柱撑膨润土光催化脱硝性能的影响

采用溶胶-凝胶法制备氟钒锰共掺改性的TiO₂柱撑膨润土，使用XRD、氮吸附、UV-vis光谱和SEM等手段对其进行了表征测试，并对其室温下的可见光催化脱硝性能进行了评价研究。结果表明，对于NO质量浓度为661 μg/m³的气体，F-V-Mn共掺TiO₂柱撑膨润土的光催化脱除效率近似达到100%，而NO质量浓度提升至1657 μg/m³时，光催化效率为81.9%，与未柱撑的F-V-Mn共掺TiO₂相比提高了33.8%。F-V-Mn共掺TiO₂柱撑膨润土上光催化脱反应速率常数最大，是V-Mn共掺TiO₂柱撑膨润土的2倍，且前者的抗水和抗SO₂中毒能力也更强。TiO₂柱撑不仅保留了膨润土的片状晶体结构，而且使膨润土层间距由0.667 nm增大至0.710 nm，吸附能力增强；同时，掺杂元素能抑制TiO₂金红石相生长，降低TiO₂禁带宽度，提高可见光响应，延长使用寿命，拓宽应用范围。     

The role of n–p junction electrodes in minimizing the charge recombination and enhancement of photocurrent and photovoltage in dye sensitized solar cells

The composite electrode comprising n-type TiO₂ and p-type NiO oxides when sensitized with Ru-dye showed short-circuit photocurrent (I_sc) of 17 mA/cm² and open-circuit photovoltage (V_oc) of 730 mV compared to I_sc of 12 mA/cm² and 700 mV for TiO₂ electrodes. Formation of a n–p junction between TiO₂ and NiO oxide layers contributes to the enhanced photocurrent, photovoltage, fill factor and efficiency. In addition to the junction effect, NiO acts as a barrier for charge recombination leading to higher cell performance. The efficiency of the NiO coated TiO₂ solar cell is 30% more than that of bare TiO₂. The negative shift of the flat-band potential of the NiO coated TiO₂ electrode compared to TiO₂ also could be one of the reasons for higher photovoltage observed for TiO₂/NiO electrode. The highest cell efficiencies were obtained immersing TiO₂ thin films in Ni²⁺ solution and converting them to NiO by firing and the optimum NiO coating thickness was found to be only a few angstroms. The energy levels of the excited dye and the band positions of TiO₂ and NiO suggest that the electron transfer from the excited dye to the underlying n-type oxide layer occurs by tunneling through the p-type NiO layer.     

锐钛矿TiO2（101）表面电子能带结构的理论研究

二氧化钛作为一种理想的光催化和光电转换半导体材料,受到了广泛的关注和研究,其表面的电子能带结构作为其本征的化学性质之一,决定着表面上氧化还原反应发生的可能性. 对二氧化钛表面电子能带结构进行深入研究对于我们从微观上认识并改良二氧化钛这一光电催化材料,以及进一步开发利用更好的光催化材料都具有非常好的指导意义. 本论文采用密度泛函理论,计算研究了锐钛矿TiO₂（101）表面的电子能带结构,并通过与金红石TiO₂（110）晶面的对比,系统分析了两个表面电子能带结构的不同以及水分子的溶剂化作用对电子能带结构的影响.     

Effect of Magnetic Carrier NiFe2O4 Nanoparticles on Physicochemical and Catalytic Properties of Magnetically Separable Photocatalyst TiO2/NiFe2O4

A series of magnetically separable photocatalyst TiO₂/NiFe₂O₄(TN) with different mass ratios of NiFe₂O₄ to TiO₂ was prepared by sol-gel method. The X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), transmission electron microscopy(TEM), ultraviolet-visible spectroscopy(UV-Vis), Brunauer-Emmett-Teller(BET) surface analysis and photoluminescence spectroscopy(PL) were used to characterize the photocatalyst TN. The XRD patterns of TN indicate that adulterating a smidgen of NiFe₂O₄ into TiO₂(about 0.1%, mass ratio) can promote the phase transformation of TiO₂, however, when the doped amount of NiFe₂O₄ surpasses 1%, the introduction of NiFe₂O₄ can inhibit the growth of TiO₂ crystal grain and reduce the size of TiO₂ crystal grain. The XPS results of TN indicate that some Fe³⁺ replace Ti⁴⁺ of the TiO₂ lattice forming Fe―O―Ti bonds. The PL analysis of TN shows that the NiFe₂O₄ nanoparticles in photocatalyst TN play the role of the effective recombination centre of the photogenerated electrons and holes, leading to the decrease in photocatalytic activity.     

ZnO-TiO2和WO3-TiO2复合薄膜光催化剂的制备与性能

采用溶胶一凝胶法在多孔钛片上制备了 ZnO-TiO₂和WO₃-TiO₂复合半导体光催化剂,用甲基橙的光催化降解反应对所得薄膜的催化活性进行评价,并通过XRD和DTA等手段对样品进行了表征.结果表明,ZnO和WO₃的掺入降低了TiO₂的相转变温度,ZnO适宜掺杂量为0.1 mol%, WO₃适宜掺杂量为0.5 mol%, ZnO-TiO₂和WO₃-TiO₂复合薄膜比纯TiO₂薄膜光催化活性分別高出77.0%和96.7%.     

NiO/TiO2异质结构纳米管阵列膜对不锈钢的光生阴极保护及其储能性能

本工作通过修饰TiO₂制备半导体复合膜,提高其光吸收和光电化学性能,以期应用于光生阴极保护。先采用阳极氧化法在Ti表面制备TiO₂纳米管阵列膜,再应用水热处理法在膜表面沉积NiO纳米颗粒,形成具有异质结构纳米管复合膜。利用扫描电子显微镜、X-射线衍射、X-射线光电子能谱、紫外-可见吸收光谱、光致发光谱和光电化学技术对制备的纳米膜进行表征。结果表明,与纯TiO₂纳米管膜比较,NiO/TiO₂纳米管复合膜的光吸收扩展到可见光区。白光照射下,其在0.5 mol·L^?1 KOH和1 mol·L^?1 CH3OH混合液中的光电流密度达到176μA·cm^?2,是纯TiO₂纳米管膜的2倍。复合膜具有良好的光生阴极保护作用,与0.5 mol·L^?1 NaCl溶液中的403不锈钢耦连后,可使其电极电位下降440 mV,在光照2.5 h再转为暗态后,因具有电荷储存能力还可继续提供约15.5 h的阴极保护效应。     

Fe-V/TiO_2催化剂NH_3选择性催化还原柴油车尾气NO_x

采用浸渍法制备了一系列不同Fe/V比例的Fe-V/TiO2催化剂,考察了催化剂在模拟柴油车尾气中催化还原NOx的催化性能,采用TG、XRD、H2-TPR、NH3-TPD和Raman光谱对催化剂进行了表征。结果表明,当Fe引入后,能显著降低V2O5在高温下的挥发,减轻了钒系催化剂在移动源的生物毒性危害。其中,Fe/V比为1∶1(Fe1-V1/TiO2)的催化剂形成了FeVO4活性中心,表现出最好的催化活性,在220~420℃NOx转化率可达到90%以上。此外,Fe1-V1/TiO2催化剂高温热稳定性较好,并且具有较强的抗硫性能。     

金属镍掺杂改进纳米TiO2的表面增强拉曼散射性能

通过溶胶-水热法合成纯的和不同量Ni离子掺杂的TiO₂纳米粒子, 将其作为表面增强拉曼散射(SERS)活性基底, 研究了金属Ni掺杂对于纳米TiO₂ SERS性能的改进. 结果表明, 适量的Ni掺杂能够在纳米TiO₂的能隙中靠近导带底的位置形成丰富的掺杂能级, 促进TiO₂-to-molecule的电荷转移过程, 进而提高纳米TiO₂基底对吸附分子的SERS增强能力, 显著改进纳米TiO₂的SERS性能.