二氧化钛纳米材料的非均相光催化本质及表面改性（英文）

非均相光催化过程是指多相多尺度体系在光辐射作用下发生的一个复杂的催化过程,被认为最有潜力解决环境污染和能源短缺问题的绿色及可再生的技术之一.在目前已经报道的各种非均相光催化剂中,TiO2纳米材料被证实是应用最广泛、光催化效果最好的催化剂,是当前国际材料、环境和能源等领域的研究前沿和热点,高性能TiO2基光催化材料的设计及改性一直是该领域的难点,其关键问题主要为:如何增强TiO2的表面光催化量子效率、促进光生载流子分离和拓展其可见光响应范围.尽管已经有很多关于TiO2光催化的综述,但大多综述集中在高性能TiO2的制备及各种改性策略研究,而对各种改性策略与光催化分子机理之间的关系阐述较少.为此,本文深入分析了TiO2纳米材料的非均相光催化本质并总结了各种表面改性策略.首先从热力学角度阐明TiO2的热力学能带能够确保其实现各种典型光催化反应(包括光催化降解、CO2还原及光解水),证实其广泛应用的可行性.然后,对TiO2光生载流子的动力学基础进行总结,证实快速的广生载流子复合以及较慢的表面化学反应动力学是限制其光催化活性提高的关键制约性因素.于此同时,对TiO2纳米材料的表面Zeta点位、超亲水性、超强酸光催化剂制备(表面羟基取代)等重要的表面化学性质也进行了详细阐述.从而可以初步得出如下结论:表面改性是设计高性能TiO2光催化材料的重中之重,并将各种改性策略浓缩在6个方面:表面掺杂和敏化,构建表面异质结,负载纳米助催化剂,增加可利用的比表面剂,利用表面氟效应以及暴露高活性晶面等.显然,表面掺杂和敏化可以减小TiO2纳米材料的禁带宽度,从而大幅拓宽其可见光吸收范围及光催化效率.而构建紧密的表面异质结可以创建界面电场,不仅可以促进光生电荷分离效率,而且可以有效提高界面电荷转移效率,最终实现异质结的高光催化效率.负载纳米助催化剂则可以大幅加快表面化学反速率,降低光生载流子的表面复合并增加其利用率,并有可能减少不期望的表面逆反应,从而实现光催化活性提升.增加可利用的比表面剂,可以有效提升光催化剂与吸附质之间的有效接触面积,缩短了载流子的传输距离以及通过多次反射与折射提升光能的利用率,从而全方位地提升TiO2纳米材料的光催化活性.对TiO2纳米材料表面进行氟化,可以增加光生羟基自由基的速率以及浓度,并可以通过调节TiO2表面酸碱性而控制其光催化选择性,从而实现高效高选择性光催化.最后,通过暴露TiO2纳米材料的高活性晶面,也可以促进光生载流子分离、增加吸附性能或羟基自由基生成速率,从而获得高光催化效率.另外,这些表面改性策略的协同效应仍是较有前景的TiO2纳米光催化剂改性技术,值得深入研究.同时,深入的光催化分子机理探索仍然是必须的,其不仅有助于发现影响TiO2纳米材料光催化活性提高的关键性制约因素,而且也可以指导开发新型的TiO2纳米光催化剂改性技术.总而言之,通过总结TiO2纳米材料在光催化、表面化学及表面改性等方面的重要进展,可为设计高效的TiO2基及非TiO2基光催化剂并应用于太阳燃料生产、环境修复、有机合成及相关的领域(如太阳能电池、热催、分离和纯化)等提供新的思路.     

乙酰丙酮金属配合物表面改性纳米二氧化钛

以乙酰丙酮稀土和乙酰丙酮铁配合物通过吸附法对纳米TiO2进行表面改性,以光催化降解甲基橙为探针反应,在紫外光照条件下考察了改性条件对纳米TiO2催化活性的影响,包括金属元素种类、配合物含量、吸附温度、溶剂用量、吸附时间等.研究表明,乙酰丙酮铁改性纳米TiO2最有效.当w[Fe(acac)3/TiO2]为0.25%,吸附温度为60℃,溶剂用量为乙醇/TiO2等于29 mL/g,吸附1.5 h时,改性后的纳米TiO2催化活性比改性前有了很大的提高.即使在普通白炽灯光照条件下,改性催化剂仍显示出很高的光催化活性,明显优于非改性的纯TiO2.改性纳米TiO2经过IR、XRD、UV-Vis、荧光、SEM-EDS和高倍光学显微镜等分析表征.     

乙二醇表面改性纳米二氧化钛的制备及其对水性聚氨酯的改性

以乙二醇(EG)和钛酸四丁酯(TBOT)为原料,采用原位表面修饰方法成功制备了乙二醇表面改性纳米TiO2(EG-TiO2);利用傅立叶红外光谱仪、X射线衍射仪、透射电子显微镜表征了其结构,采用热重分析仪测定了其热稳定性.结果表明,经表面修饰的纳米二氧化钛在水性聚氨酯皮革涂饰剂(WPU)基体中分散良好;将EG-TiO2添加到WPU中能显著提高其抗紫外线性能、热稳定性及耐磨性能.     

硅烷偶联剂改性的二氧化钛光催化降解气相苯

 用硅烷偶联剂KH-570对二氧化钛光催化剂进行了改性,制备了一种新型光催化剂. 以苯作为 模拟气体,在静态反应装置中考察了该催化剂的光催化性能. 结果表明,KH-570能显著提高 二氧化钛对气相苯的光催化降解性能,其转化率是纯二氧化钛的2.5倍. 采用红外光谱和X射线光电子能谱对催化剂进行了表征.     

二氧化钛表面光学特性与光催化活性的关系

本文考察了二氧化钛经氢气氛热处理后对其光催化降解苯酚活性的影响。结果ＤＲＳ，ＦＳ，ＸＲＤ等研究手段，发现二氧化钛光催化降解苯酚的活性与其光学特性（吸收光能力和荧光发射强度）有较好的一致性，而光学特性来自表面态。由此，提出了二氧化钛光学表面态的概念，认为与光催化活性密切相关的二氧化钛光学表面态的性质，是由这些钛羟基和低价钛的数量及比例决定的。     

二氧化钛微粒存在下表面活性剂光催化分解机理的研究

半导体微粒子(二氧化钦等)在光照射下产生强烈的氧化能力,可以把水和空气中的许多难分解有毒有机污染物氧化分解为二氧化碳、水等无机物。该方法分解速度快、除净度高,有着很大的应用前景^[1~3]。在过去几年里,我们广泛地报导了在二氧化钦半导体微粒子催化下表面活性剂^[3,4]、农药^[5]氰化物困等环境污染物的光催化分解。烷基、芳香基及含氧碳氢基团可被氧化分解为二氧化碳和水^[4];有机化合物中的卤素^[5]、磷川、硫^[8]氮^[9]原子分别被光分解为卤素离子、磷酸根离子、硫酸根、按和硝酸根离子。因多相光催化反应十分复杂,目前对光催化分解过程,特别是中间化合物的生成及其浓度变化了解很少,甚至连光致电子及空穴的反应也并不十分明确。     

改性二氧化钛纳米棒的制备及光催化有机污染物研究

为了改善纳米二氧化钛的光催化活性,通过水热法制备了氮钨共掺杂二氧化钛纳米棒。通过扫描电镜(SEM),X射线衍射(XRD),透射电镜(TEM),X射线光电子能谱(XPS)和紫外可见光吸收光谱 (UV-VIS)等对产物进行了相关表征。结果显示：与未掺杂的二氧化钛相比,氮钨共掺杂的二氧化钛纳米棒在可见光区域显示出了较强的光催化活性。因为氮钨阳离子的掺入拓宽了可见光的吸收区域。     

镍离子表面处理对二氧化钛光催化活性的影响

采用溶胶-凝胶法制备出纳米TiO2和TiO2-Ni催化剂. 光催化降解对氯苯酚实验证明, TiO2-Ni催化剂的紫外、可见光催化活性均高于TiO2. FTIR和Raman结果表明, Ni2+离子被化学吸附在TiO2表面形成ONiOO表面物种. SPS的结果表明, TiO2-Ni表面ONiOO物种的表面态能级在价带上方2.84 eV. 该能级既能产生可见光响应, 又有效地促进了光生载流子的分离, 使催化剂紫外、可见光催化活性提高.     

氟掺杂提高纳米二氧化钛光催化活性的研究进展

纳米二氧化钛(TiO2)具有光催化活性高、无毒、化学性质稳定、成本低等优点,是目前最具发展前景的光催化剂。但TiO2的宽禁带和低量子效率限制了它的实际应用。因此,对TiO2进行改性研究,实现TiO2的可见光响应和提高其量子效率成为研究的热点。氟掺杂不仅能够使TiO2具有可见光催化活性,而且可提高其紫外光催化活性。本文综述了氟掺杂TiO2的制备,氟掺杂提高TiO2光催化活性的机理、氟与其他元素共掺杂TiO2的研究进展。     

二氧化钛纳米管阵列的制备、改性及应用

二氧化钛因其在光催化、染料敏化太阳电池、生物医药等应用领域表现出优异性能而成为材料科学领域重点研究的化合物之一。本文介绍了近年来阳极氧化法制备不同形貌的TiO2纳米管(TiO2NTs)阵列,探讨了电解液、阳极氧化时间、电压三个因素对TiO2纳米管形貌的影响,综述了掺杂、复合、表面修饰这三种能对TiO2纳米管进行化学或物理修饰的改性手段以及改性后的TiO2纳米管阵列在光催化、太阳能电池、生物医学、传感等领域的应用研究进展。最后,指出国内外针对二氧化钛纳米管阵列研究现状所存在的问题,并对今后的研究工作提出了展望。     

硅铝氧化物二元包覆钛白粉颗粒的有机改性

在二元包覆SiO₂,Al₂O₃薄膜的基础上,用钛酸酯偶联剂、硅烷偶联剂及三乙醇胺、季戊四醇对亚微米TiO₂颗粒表面进行有机改性.考察了改性条件对颗粒表面改性结果的影响.通过疏水性试验和润湿性试验对改性前后TiO₂颗粒的表面特性进行了表征.高温裂解色谱、热重分析、X光电子能谱的测试结果表明,不同改性剂与颗粒表面存在不同程度的化学键合作用.分析了改性剂在颗粒表面的包覆状态与结构.     

A novel Fe（OH）3/TiO2 nanoparticles and its high photocatalytic activity

A very simple and controllable approach was proposed to synthesize novel Fe(OH)_3/TiO_2 nanoparticles.Compared with neat TiO2,the Fe(OH)_3/TiO_2 increased the rate of the photocatalytic degradation of methyl orange at pH 6.0 by more than five times, showing photocatalytic activity as excellent as P25.This enhancing effect is mainly attributed to the ferric hydroxide deposits as the electron scavenger and the enriched surface hydroxyl groups.     

TiO2表面光催化基元过程

在过去的几十年里,得益于二氧化钛(TiO₂)作为光催化剂在光催化分解水、污染物降解方面的潜在应用,人们对TiO₂光催化剂的开发、改良以及TiO₂表面光催化机理的基础研究方面都投入了巨大的精力。因此,在超高真空环境下,利用不同的实验和理论方法,人们对TiO₂表面(特别是金红石TiO₂(110)表面)的热催化和光催化过程进行了大量的研究,以此来获得上述重要反应中的一些机理性的信息。本文中,将从TiO₂的物质结构以及电子结构开始,然后着重介绍TiO₂表面光生电荷(电子和空穴)的传输、捕获以及电子转移动力学方面的进展。在此基础上,总结了甲醇在金红石TiO₂(110)、TiO₂(011)以及锐钛矿TiO₂(101)表面光化学基元反应过程的一些实验结果。这些结果不仅能增进我们对表面光催化基元过程的认识,同时也能激励我们进一步去研究表面光催化基元过程。最后,基于现有光化学实验结果,简短地讨论了我们对光催化反应机理的一点看法,并提出了一个可能的光催化模型,这可以引起人们对光催化反应机理更全面的思考。     

Effects of 3,4-dihydrophenyl groups in water-soluble phospholipid polymer on stable surface modification of titanium alloy

The surface of a titanium (Ti) alloy substrate was modified by a simple and quick process using a water-soluble polymer, and the effects of 3,4-dihydroxyphenyl (DHP) groups in the polymer side chain on the modification process were examined. The polymers (PMDP) composed of both 2-methacryloyloxyethyl phosphorylcholine (MPC) unit and 3,4-dihydroxyphenyl methacrylate unit were synthesized for surface anchoring. The Ti alloy substrate was coated with PMDP using an aqueous solution of the polymer. A PMDP layer with a thickness of 20 nm was formed on the Ti alloy substrate simply by dip coating for 10 s without drying. Even when the Ti alloy substrate with PMDP coating was immersed in the aqueous medium for 1 week, no change in the thickness was observed, i.e., the PMDP layer was bound to the surface very stably. Oxidation of the DHP groups reduced the stability of the polymer layer significantly. Thus, the DHP groups play a significant role in achieving stable binding. Protein was adsorbed on the Ti alloy substrate; however, this was not observed for the PMDP-coated Ti alloy substrate. In conclusion, we confirmed the effects of DHP groups in PMDP on the stability of the coating on the Ti alloy substrate. Moreover, we found that surface treatment using PMDP was simple, quick, and reliable, and thus, it has great potential for improving biofouling of Ti alloy substrates used in medical devices.     

Thiobencarb Degradation by TiO2 Photocatalysis: Parameter and Reaction Pathway Investigations

The present study deals with the photocatalytic degradation of the thiocarbamate herbicide, thiobencarb (TBC), in the presence of TiO₂ particles and UV‐A (λ = 365 nm) radiation. Results show rapid and complete oxidation of TBC after 90 min, and slightly over 70% of TBC was mineralized after 32‐h treatment. Factors such as solution pH, TiO₂ dosage, and the presence of anions are found to influence the degradation rate. The establishment of the reaction pathway is made possible by a thorough analysis of the reaction mixture identifying the main intermediate products generated. Results suggest that possible transformation pathways may include hydroxylation, dealkylation and C—S bond cleavage processes. The possible degradation pathways are proposed and discussed on the basis of the evidence of oxidative intermediate formation.     

Synthesis of visible light-activated TiO2 photocatalyst via surface organic modification

A visible light-activated TiO₂ photocatalyst was successfully synthesized by the surface organic modification to sol-gel-hydrothermal synthesized TiO₂. The surface hydroxyls of TiO₂ nanoparticles reacted with the active -NCO groups of tolylene diisocyanate (TDI) to form a surface complex that was confirmed by the FT-IR and XPS spectra. Due to the existence of surface complex, the absorption edge of as-prepared TDI-modified TiO₂ nanomaterial extended well into visible region. Compared with unmodified TiO₂ and Degussa P25, the TDI-modified TiO₂ photocatalysts showed higher activity for the photocatalytic degradation of methylene blue under visible light irradiation.     

Synthesis and surface modification of mesoporous mcm-41 silica materials

Surface modification offers a great opportunity to adjust both the pore diameter and surface properties of MCM-41 type organic–inorganic hybrid materials which result in materials of improved hydrothermal and mechanical stability. Therefore, MCM-41 silica, surface modified with organic ligands, are promising systems with engineered properties and attractive for advanced applications. In the present study, after optimization of the reaction conditions highly ordered MCM-41 silica spheres with uniform mesopores were prepared by the pseudomorphic transformation route. The effect of functionality and alkyl chain length of the alkyl ligands during surface modification was probed by using butyl and octylsilanes with two different functionalities. Due to steric hindrance, the longer chains are assumed to bind only on the outer silica surface and near the entrance of the pores, while the shorter chains are also able to bind to the interior mesopore walls. The resulting materials were comprehensively characterized before and after surface modification using nitrogen sorption techniques, XRD, SEM, solid-state NMR spectroscopy and FTIR spectroscopy. From chromatographic test measurements it was found that the separation power primarily depends on surface coverage and alkyl chain length. On the basis of the present data, surface modified mesoporous silica of MCM-41 type are very promising candidates for future chromatographic applications.     

Corrosion resistance and bioactivity of titanium after surface treatment by three different methods: ion implantation,alkaline treatment and anodic oxidation

The paper compares the effects of various surface modifications, ion implantation, alkaline treatment and anodic oxidation, upon the corrosion resistance and bioactivity of titanium. The chemical composition of the surface layers thus produced was determined by XPS, SIMS and EDS coupled with SEM. The structure of the layers was examined by TEM, and their phase composition by XRD. The corrosion resistance was determined by electrochemical methods after the samples were exposed to the test conditions for 13 h. The bioactivity of titanium was evaluated in a simulated body fluid at a temperature of 37°C after various exposure time.     

纳米TiO2的有机酸改性

纳米TiO2粉体独特的光催化作用、颜色效应以及紫外屏蔽等功能使其在汽车工业、防晒化妆品、环保等方面有着广阔的应用前景。未经表面处理的纳米TiO2表面疏油,不易在有机介质中分散,直接影响到TiO2性能的发挥。