具有可见光活性的光催化剂研究进展

简述了可见光光催化机理,该机理与紫外光光催化机理的不同之处在于其电荷传输与分离机制。综述了近年来具有可见光活性的光催化材料的研究进展。贵金属、过渡金属及其化合物的掺杂、染料光敏化、氮掺杂和在适当载体上的负载可使复合物的复合禁带宽度小于TiO2的禁带宽度,从而使TiO2的吸收带发生红移,实现可见光响应,其中,氮掺杂ZnO或氮掺杂TiO2及其复合半导体具有较好的可见光光催化活性,另外一些氮氧化物、氮化物及许多钙钛矿型半导体可以作为可见光分解水的有效催化剂。     

金属掺杂二氧化钛的研究进展

二氧化钛(TiO2)是一种比较理想的光催化剂,具有无毒、生产成本低、耐光照等特点。但是较宽的禁带使其应用受到一定的限制,通过掺杂可以改变禁带的宽度提高TiO2的光催化和光电性能。掺杂可分为非金属掺杂和金属掺杂,非金属掺杂一般是拓展其光吸收范围,提高对可见光的响应能力。金属掺杂为了抑制电子—空穴的复合,提高光催化性能,此外TiO2掺杂金属后表现出光、电、磁性能。     

非金属掺杂的第二代二氧化钛光催化剂研究进展

寻求廉价、环境友好并具有可见光光催化活性的第二代光催化剂将是光催化发展进一步走向实用化的关键。氮掺杂的TIO2是新发现的具有可见光光催化活性的复合光催化剂,非金属掺杂可以使复合物的复合禁带宽度小于TIO2的禁带宽度,从而使TIO2的吸收边向可见光移动。对TIO2的氮、碳、硫、卤素掺杂国内外研究现状进行了系统评述,分析了提高TIO2可见光活性的原因,指出非金属元素特别是氮元素的阴离子掺杂是在不降低紫外光催化活性的基础上实现可见光响应的较好方法。     

掺杂改性TiO2可见光光催化剂研究的最新进展

纳米TiO2在紫外光照射下具有良好的光催化活性,在环境污染物治理方面具有重要的应用前景。为提高TiO2对可见光的吸收,常常需要对TiO2进行掺杂改性以缩小其禁带宽度。本文综述了近些年来国内外在金属掺杂、非金属掺杂、金属-金属共掺杂、金属-非金属共掺杂、非金属-非金属共掺杂以及杂多酸盐掺杂改性TiO2光催化剂方面的最新进展,并对TiO2可见光光催化剂的研究进行了展望。     

N-TiO2/g-C3N4复合光催化剂的制备及其光催化性能

采用水热法制备N掺杂TiO2,将其与二氰二胺混合进行高温焙烧合成N-TiO2/g-C3N4复合光催化剂。采用XRD、UV-Vis、N2吸附-脱附和SEM等对催化剂进行微观结构表征,以200W氙灯模拟光源并过滤掉420nm以下的紫外光,对比研究TiO2、g-C3N4、N-TiO2和复合光催化剂对罗丹明B的可见光降解性能。结果表明,N掺杂后TiO2的禁带宽度降低,催化活性提高;而复合光催化剂可见光吸收边距相对N-TiO2进一步红移,禁带宽度为2.75eV,降解罗丹明B的一级动力学常数k可达0.12158min-1,是g-C3N4、N-TiO2的2倍;复合催化剂重复使用4次后,对罗丹明B的降解率仍达92%以上,表明催化剂具有较好的光催化活性和稳定性。     

镧铁共掺杂二氧化钛纳米线阵列的可见光催化性能

采用溶胶-电泳沉积技术,在多孔氧化铝模板中合成了二氧化钛(TiO2)纳米线阵列结构.研究了La3 /Fe3 共掺杂对TiO2纳米线可见光催化性能的影响,并分别与La3 ,Fe3 单掺杂TiO2纳米线可见光催化性能进行了比较.结果表明:与La3 ,Fe3 单掺杂TiO2纳米线相比,La3 /Fe3 共掺杂TiO2纳米线具有更高的可见光催化活性,光照4 h对甲基橙的降解率就达到了90%以上,大幅度提高了Ti02的可见光催化活性,这是因为2种不同体系离子的协同作用,不仅有效抑制了光生电子和空穴的复合,而且明显降低了TiO2的禁带宽度,由3.24降低到2.38.研究还表明:TiO2纳米线阵列极大的比表面积以及表面特有的性质和结构是掺杂改性TiO2纳米线具有较高可见光催化活性的重要因素.     

TiO2可见光催化剂的研究进展及其应用

TiO2是当前最具应用潜力的光催化剂之一,但仍然存在不足,因为TiO2在禁带窄(为3.2eV)、在紫外光照下才显示出高的活性,为了有效地利用太阳光,希望其在可见光下也能具有光催化活性.因此,TiO2可见光化一直是研究热点.目前TiO2可见光化的研究取得了一定进展,金属离子掺杂、非金属离子掺杂、离子注入、复合半导体、贵金属沉淀以及染料光敏化等方法都不同程度地实现了TiO2可见光化.本文综述了目前的研究现状,并对今后的研究提出了展望.     

金属离子掺杂改性纳米TiO2的能带结构及其光催化性能

为了研究纳米TiO2金属离子掺杂的改性机理,使用Materials Studio软件的Dmol3模块分别对Fe3+、Ag+、Pt4+、La3+4种金属离子掺杂纳米TiO2的能带结构进行分析。分子模拟表明,金属离子掺杂使TiO2的禁带宽度、Fermi能级和禁带偏移发生变化,影响了TiO2的光催化性能。光催化反应表明,Ag+掺杂后TiO2的禁带宽度为1.09eV、Fermi能级为-0.294eV、禁带向下偏移0.28eV,纳米TiO2光催化剂对聚乙二醇模拟废水的处理效果最好。     

UV-Vis光谱研究Al3+,Zn2+,Cu2+掺杂对TiO2薄膜光学禁带宽度的影响

通过采用溶胶一凝胶法制备了稳定的TiO2溶胶，在此基础上制备了Al^3＋，Zn^2＋，Cu^2＋等金属离子氧化物掺杂的复合TiO2薄膜。采用X射线衍射、紫外一可见分光光度计以及NKD-7000W薄膜分析系统对所得薄膜晶相组成、光学性质以及禁带宽度等进行了表征。结果表明，这些金属氧化物与TiO2的复合薄膜体系中，形成了单一的锐钛矿相TiO2，与纯TiO2薄膜相比，复合薄膜中TiO2纳米粒子平均尺寸在一定程度上减小了。同时，复合TiO2薄膜的光学透过率以及光学禁带宽度均随着添加量的增加而规律性变化。     

Zn/TiO_2/泡沫镍可见光下光催化氧化水体中As(Ⅲ)

采用阴极电沉积法在泡沫镍上负载Zn2+掺杂TiO2,制得Zn/TiO2/泡沫镍光催化剂,利用XRD、SEM、UVVis、CA对其进行了晶体结构、表观形貌、光学及光电特性的分析,并研究了可见光催化氧化As(Ⅲ)的反应性能。结果表明,掺杂Zn2+将TiO2禁带宽度减少0.05 e V,使起始吸收带边红移。Zn/TiO2/泡沫镍光电流密度为非掺杂的5倍。Zn/TiO2/泡沫镍可见光催化氧化As(Ⅲ)的去除率为非掺杂的1.8倍,羟基自由基在光催化过程中起重要作用。光催化后溶液未检测到镍基材溶出,可应用于处理饮用水。     

具有可见光催化活性的TiO2系光催化剂研究进展

由于受激发波长的限制，TiO2只能利用太阳能中不足5％的紫外光。本文较为详细NTiO2可见光催化剂的制备、性能及应用进行了综述。研究表明，通过金属及非金属离子掺杂改性、离子注入以及染料光敏化等方法可以将TiO2光催化反应红移到可见光区域进行。     

Visible light-active sub-5 nm anatase TiO2 for photocatalytic organic pollutant degradation in water and air,and for bacterial disinfection

Visible-light-sensitive sub-5 nm anatase titanium dioxide (TiO₂) nanoparticles (NPs) were fabricated without any doping and calcination treatments. The energy band gap was effectively narrowed to ~ 2.98 eV. The surface and subsurface hydroxyl defects were ascertained as the origin for the band gap narrowing and for the efficient azo-based dye degradation in water and formaldehyde decomposition in air, as well as disinfection of Staphylococcus aureus bacteria, under visible light irradiation.     

Synthesis and visible‐light‐derived photocatalysis of titania nanosphere stacking layers prepared by chemical vapor deposition

BACKGROUND: In this study, visible‐light‐derived photocatalytic activity of metal‐doped titanium dioxide nanosphere (TS) stacking layers, prepared by chemical vapor deposition (CVD), was investigated. The as‐grown TS spheres, having an average diameter of 100–300 nm, formed a layer‐by‐layer stacking layer on a glass substrate. The crystalline structures of the TS samples were of anatase‐type. RESULTS: Ultraviolet (UV) absorption confirmed that metallic doping (i.e. Co and Ni) shifted the light absorption of the spheres to the visible‐light region. With increasing dopant density, the optical band gap of the nanospheres became narrower, e.g. the smallest band gap of Co‐doped TS was 2.61 eV. Both Ni‐ and Co‐doped TS catalysts showed a photocatalytic capability in decomposing organic dyes under visible irradiation. In comparison, Co‐doped TiO₂ catalyst not only displays the adsorption capacity, but also the photocatalytic activity higher than the N‐doped TiO₂ catalyst. CONCLUSION: This result can be attributed to the fact that the narrower band gap easily generates electron–hole pairs over the TS catalysts under visible irradiation, thus, leading to the higher photocatalytic activity. Accordingly, this study shed some light on the one‐step efficient CVD approach to synthesize metal‐doped TS catalysts for decomposing dye compounds in aqueous solution. Copyright © 2010 Society of Chemical Industry     

氮掺杂光催化剂的研究进展

光催化剂尤其是二氧化钛及一类钛基铌基固体粉末在能源和环境问题上的应用有巨大潜质。然而,限制于其自身的带隙能量,对可见光的响应能力较弱,为对催化剂进行改性采取掺杂方法,对该类物质氮掺杂改性进行总结,阐述目前现阶段在掺氮方面存在的问题和争议。     

Experimental and theoretical studies of KxZn1-xO

In this paper, K-doped ZnO nanocrystalline powders were prepared by the sol-gel method at 500 °C. The effects of potassium (K) doping on the particle size, phase composition, and light absorption properties of zinc oxide nanocrystals were investigated by X-ray diffraction, transmission electron microscopy and ultraviolet–visible spectroscopy. The main crystalline phase of the powders before and after K doping is wurtzite ZnO. With the increased K doping amount, the purple and blue luminescent peaks are enhanced. The band gap of the sample obtained from the light absorption spectra initially increased with the K doping amount, then decreased, and increased again with the K doping amount, which is consistent with the theoretical calculation results. The calculated energy band and density of states results show that when the K doping amount is small, the band gap is reduced because the K doping forms the impurity level and the conduction band moves downward. This decrease is due to the two impurity levels generated at the bottom of the valence band.     

TiO2可见光催化研究进展及其应用前景

综述了最近二氧化钛可见光催化改性的研究进展,并展望了二氧化钛光催化剂的应用前景。二氧化钛可见光催化剂改性方法包括:金属离子掺杂、非金属离子掺杂、半导体复合、表面光敏化及共掺杂等主要方法。其中运用最广泛的方法是共掺杂,因为共掺杂能集合其他改性方法的优点,可以同时在降低禁带宽度、提高吸光能力与降低电子与空穴复合等方面提高二氧化钛的性能。同时总结了其最近在环境污染物降解、有机物还原、太阳能电池等多方面的实验研究,展示其在多个领域的应用潜力。最后展望了未来二氧化钛可见光催化剂的发展方向及其应用前景。     

Plasma dynamic synthesis of highly defective fine titanium dioxide with tunable phase composition

Titanium dioxide is currently one of the most known promising photocatalysts. However, its use in the visible light range is limited due to its high energy gap. In this work, to solve the mentioned problem, it is proposed to obtain highly defect structures of titanium dioxide by means of a high-energy plasma dynamic synthesis method. It possible to synthesize TiO₂ Titanium dioxide powders with a tunable ratio of rutile and anatase modifications, as well as a particle size distribution were synthesized, by optimizing the synthesis conditions, including the process energy and parameters of the gaseous medium. The formation of shock-wave structures in the pulsed synthesis process results in obtaining fine particles of rutile and anatase with a highly defective crystal structure. The final product was revealed to have an extended working absorption spectrum region and a reduced band gap (2.74 eV). A possibility of photocatalytic applications for the synthesized TiO₂ powder was demonstrated in measurements of photocurrent density with time (j-t) under intermittent visible light irradiation.     

Remarkably enhanced photocatalytic activity by nickel nanoparticle deposition on sulfur-doped titanium dioxide thin film

To enhance the photocatalytic performance of titanium dioxide, the structures of both bulk and surface were modified. Doping of sulfur atoms to be substituted for lattice oxygen atoms of titanium dioxide was carried out to extend the light absorption by atmosphere-controlled pulsed laser deposition, which allows direct preparation of impurity-included thin film such as sulfur-doped titanium dioxide. On the other hand, to enhance the surface catalytic reaction, nickel nanoparticles were deposited at the thin film substrate by chemical vapor reductive deposition method, which is a novel preparation technique of metallic nanoparticles on the substrate surface. Obtained sulfur-doped titanium dioxide was found to possess sensitivity to visible light with the wavelength up to 550 nm, indicating the photocatalytic activity in visible region. Sulfur doping induced the dye degradation activity under visible light irradiation. When nickel nanoparticles were deposited, a remarkable enhancement of the hydrogen evolution activity through ethanol decomposition of more than 20 times as much as unmodified titanium dioxide thin film was accomplished. In addition, the stability of sulfur atom doped into titanium dioxide structure was investigated.