硼硫共掺杂TiO2的光催化性能及掺杂机理

采用水热法制备了硼硫共掺杂的TiO2光催化剂(TiO2-B-S),并用其光催化降解甲基橙.结果表明,在240℃下水热反应12h时制得的TiO2-B-S具有较高的催化活性,紫外光照射50min和太阳光照射230min时对甲基橙的降解率分别达99.8%和81%.X射线粉末衍射、紫外-可见漫反射光谱和X射线光电子能谱等研究表明,TiO2-B-S为锐钛矿晶型,硫硼掺杂能抑制TiO2粒径的生长;TiO2-B-S同时具有较高的紫外光和可见光活性的原因可能是掺杂的硼以B3 进入晶格中,导致TiO2晶格畸变,带隙变窄.掺杂的硼和硫还提高了TiO2的表面酸度和对可见光的吸收.     

N-P-TiO2纳米粒子的溶胶-水热制备及太阳光下光催化降解4-氯酚性能

以尿素和磷酸为掺杂剂、冰醋酸为抑制剂,利用溶胶-水热技术制备了介孔锐钛矿型N-P-TiO2片状纳米粒子;以4-氯酚溶液在模拟太阳光照射下的光催化降解评价其光活性;结合XRD,TEM,BET,XPS,DRS,PL和ζ-电位分析,探讨了N和P掺杂对TiO2光活性的影响机制.结果表明,与未掺杂、N或P单掺杂TiO2相比,N-P共掺杂TiO2具有更高的光催化降解4-氯酚活性.N-P共掺杂TiO2的可见光响应是由N 2p,P 3p分别与O 2p轨道杂化导致带隙窄化引起的.N-P共掺杂产生协同作用,进一步改善TiO2的表面织构特性,增加表面羟基,抑制光生e-/h+复合,增强表面酸性提高其水分散性,导致N-P共掺杂TiO2的光活性提高.     

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。     

液相沉积法制备光催化活性TiO2薄膜和纳米粉体

采用液相沉积法 ,在 3 5℃通过向六氟钛酸铵水溶液中添加硼酸和结晶诱导剂锐钛矿型TiO2 纳米晶 ,沉积出具有光催化活性的TiO2 薄膜和纳米粉体 .用XRD ,AFM ,阶梯仪 ,UV vis ,BET法对TiO2 薄膜和粉体的沉积条件、结构、厚度和性能进行了测定和表征 ,并用亚甲兰的降解 ,评价了TiO2 薄膜和纳米粉体的光催化活性 .结果表明 ,当反应物六氟钛酸铵与硼酸的摩尔比为 1∶2～ 1∶4时 ,沉积的粉体和薄膜含有锐钛矿相TiO2 ;经 3 0 0℃热处理的TiO2 薄膜和纳米粉体具有最高的光催化活性 ,它的光催化活性是未经热处理前的 5倍 .本文还解释了经 3 0 0℃热处理的薄膜和纳米粉体具有最高光催化活性的原因     

掺Ce^3＋纳米TiO2的制备及光催化性能

用溶胶-凝胶法技术制备了掺杂Ce^3＋的纳米TiO2复合粒子，并对其进行了XRD，TEM和DRS表征及光催化活性检验。水中苯酚的Ce^3＋／TiO2光催化降解效果和矿化率分别采用降解率和COD表征。结果表明，未经掺杂的TiO2与掺杂Ce^3＋的TiO2均为锐钛和金红石的混合晶型；掺杂抑制了TiO2晶粒的生长，使得TiO2粒径明显变小，其颗粒大小为10mm左右。用DRS表征微粒的光吸收能力和光吸收带边移动情况，发现掺杂导致了TiO2光吸收能力增强及吸收带边红移。通过对苯酚的光催化氧化降解研究，发现铈的掺杂量有一适宜值，当Ce^3＋在0．08％-0．4％之间时，随着掺杂量的增加光催化活性提高；当Ce^3＋在0．5％～3．0％之间时，随着掺杂量的增加光催化活性降低；Ce^3＋=0．4％时，TiO2光催化活性最高。     

掺杂金属离子改性的TiO2薄膜光催化剂的研制

采用溶胶-凝胶法制备TiO2薄膜光催化剂，着重考察了掺杂铈、镧、钨等金属离子改性的TiO2薄膜的光催化活性，研究了其紫外-可见光透过性能，甲基橙水溶液的光催化降解实验表明：掺杂铈、镧、钨三种金属离子后，TiO2薄膜的光催化活性均有不同程度的提高，最佳掺杂浓度分别为3．0％、1．0％、0．5％，其中掺杂铈的TiO2薄膜光催化活性最高。     

钬掺杂提高TiO2纳米晶光催化活性的光谱性能机制研究

采用酸催化的溶胶-凝胶法制备了未掺杂和掺杂0.5%Ho(摩尔分数)的纳米TiO2光催化剂,以甲基橙的光催化降解为探针反应,评价了其光催化活性。运用XRD,TEM,EDS,FT-IR,UV-Vis DRS以及PL光谱表征技术考察了Ho掺杂对纳米TiO2的微晶尺寸、晶体结构、表面组成与光学性能的影响,并对改性机制作了探讨。结果表明,Ho掺杂可以抑制TiO2由锐钛矿相向金红石相的转变,阻碍TiO2晶粒增长,使TiO2的光吸收带边发生蓝移,增加表面羟基含量,促进光生载流子分离,从而使Ho掺杂TiO2样品光催化降解甲基橙的能力显著增强。     

TiB2/均相硼掺杂TiO2核/壳结构提升光催化氧化水产氧活性

光催化可实现污染物降解、分解水制氢和CO2还原等多种氧化还原反应, 因而受到了广泛关注. 光催化材料中光生电荷的数目与氧化还原能力直接影响光催化反应效率, 在许多光催化反应中, 光生空穴氧化反应被认为速控步骤. 以光催化分解水为例, 质子的还原是单电子过程, 水氧化产生氧气则涉及四个电子. 空穴的高能量不仅可赋予其高的氧化能力,还能提高其迁出表面的能力, 因此具有重要研究价值.我们组的前期工作表明, 以TiB2作为前驱体, 采用水热合成和焙烧两步法可制备出间隙硼掺杂的金红石相或锐钛矿相TiO2, 间隙硼掺杂可显著降低价带顶, 提升光催化氧化水产氧性能. 然而, 在已有的结果中, 间隙硼掺杂浓度在TiO2中均呈现从内向外逐渐增加的梯度分布, 这意味着硼掺杂浓度有限, 且表层更低的价带顶不利于体相光生空穴向表面迁移, 因此亟需实现TiO2中均相的间隙硼掺杂.本文以湿化的氩气为水解环境, 将水解过程限域在TiB2的表面以减少硼原子流失; 同时提高水解温度, 使残留的硼原子形成间隙掺杂, 避免其在二次焙烧时扩散, 从而在TiB2核的表面所形成的TiO2壳层中实现均相间隙硼掺杂, 显著提高了光催化氧化水产氧活性. 多种表征结果表明, 直径约为6-10 μm的TiB2核表面形成了厚约400 nm的TiO2壳层, 在TiO2/TiB2中TiO2壳层重量比约为30%, TiO2壳层中锐钛矿相TiO2占比为65 wt%, 金红石相TiO2占比为35 wt%. TiO2壳层中间隙硼为均相分布, 硼掺杂显著降低了价带顶位置, 提高了光生空穴的氧化能力, 从而使得TiB2/TiO2展现出比未掺杂的金红石、锐钛矿相及两者混合相的TiO2均具有更高的光催化氧化水产氧的能力.     

Fe、N共掺杂TiO2纳米管阵列的制备及可见光光催化活性

应用电化学阳极氧化法结合浸渍和退火后处理制备了Fe和N共掺杂的TiO2纳米管阵列光催化剂,并用场发射扫描电镜(FESEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和俄歇电子能谱(AES)仪对其进行了表征.结果表明,Fe、N共掺杂对TiO2纳米管阵列的形貌和结构没有明显影响,Fe和N均掺入了TiO2晶格.紫外-可见(UV-Vis)漫反射光谱显示Fe和N共掺杂TiO2纳米管阵列的吸收带边较纯TiO2纳米管阵列和单一掺杂TiO2纳米管阵列红移,可见光吸收增强.以可见光催化降解罗丹明B(RhB)考察了材料的光催化活性,Fe和N共掺杂TiO2纳米管阵列对RhB的降解速率较纯TiO2纳米管阵列和单一掺杂TiO2纳米管阵列明显提高,证明了Fe、N共掺杂产生的协同效应提高了TiO2纳米管阵列在可见光照射下的光催化活性.     

Sm掺杂对TiO2薄膜光催化性能的影响

 采用溶胶-凝胶法、浸渍-提拉法制备了不同形式和不同含量Sm掺杂的锐钛矿晶型TiO2的光催化剂薄膜. 采用X射线衍射、UV-Vis光谱及电化学实验对所制得的TiO2光催化剂薄膜进行了表征,并通过甲基橙溶液的光催化降解实验评价了其光催化活性. 结果表明,与未掺杂的TiO2薄膜相比,Sm掺杂的TiO2薄膜的UV-Vis吸收光波长向长波方向移动,并且光照开路电压也相应提高; 适量Sm掺杂可以明显提高TiO2薄膜的光催化活性,最佳Sm掺杂量为x(Sm3+)=0.5%; 在各种掺杂形式中以表层Sm掺杂的Sm-TiO2(S)薄膜的光催化活性最好. 讨论了Sm掺杂提高TiO2薄膜光催化活性的机理.     

Preparation, phase transformation and photocatalytic activities of cerium-doped mesoporous titania nanoparticles

Cerium-doped mesoporous TiO₂ nanoparticles with high surface area and thermal stable anatase wall were synthesized via hydrothermal process in a cetyltrimethylammonium bromide (CTAB)/Ti(SO₄)₂/Ce(NO₃)₄/H₂O system. The obtained materials were characterized by XRD, FESEM, HRTEM, FTIR spectroscopy, nitrogen adsorption and DRS spectra. Experimental results indicated that the doping of cerium not only increased the surface area of mesoporous TiO₂ nanoparticles, but also inhibited the mesopores collapse and the anatase-to-rutile phase transformation. Moreover, the undoped, doped anatase mesoporous nanoparticles exhibit higher photocatalytic activity than commercial photocatalyst (Degussa, P25), but the maximum photodegradation rate corresponds to the undoped mesoporous TiO₂ nanoparticles. The lower photocatalytic activities of cerium-doped samples compared with undoped one may be ascribed to that the doped cerium partially blocks titania's surface sites available for the photodegradation and absorption of Rhodamine B (RB).     

Understanding the synergistic effects,optical and electronic properties of ternary Fe/C/S‐doped TiO2 anatase within the DFT + U approach

Although TiO₂ is an efficient photocatalyst, its large band gap limits its photocatalytic activity only to the ultraviolet region. An experimentally synthesized ternary Fe/C/S‐doped TiO₂ anatase showed improved visible light photocatalytic activity. However, a theoretical study of the underlying mechanism of the enhanced photocatalytic activity and the interaction of ternary Fe/C/S‐doped TiO₂ has not yet been investigated. In this study, the defect formation energy, electronic structure and optical property of TiO₂ doped with Fe, C, and S are investigated in detail using the density functional theory + U method. The calculated band gap (3.21 eV) of TiO₂ anatase agree well with the experimental band gap (3.20 eV). The defect formation energy shows that the co‐ and ternary‐doped systems are thermodynamically favorable under oxygen‐rich condition. Compared to the undoped TiO₂, the absorption edge of the mono‐, co‐, and ternary‐doped TiO₂ is significantly enhanced in the visible light region. We have shown that ternary doping with C, S, and Fe induces a clean band structure without any impurity states. Moreover, the ternary Fe/C/S‐doped TiO₂ exhibit an enhanced photocatalytic activity, a smaller band gap and negative formation energy compared to the mono‐ and co‐doped systems. Moreover, the band edges of Fe/C/S‐doped TiO₂ align well with the redox potentials of water, which shows that the ternary Fe/C/S‐doped TiO₂ is promising photocatalysts to split water into hydrogen and oxygen. These findings rationalize the available experimental results and can assist the design of TiO₂‐based photocatalyst materials.     

Effect of Erbium on the Photocatalytic Activity of TiO2/Ag Nanocomposites under Visible Light Irradiation

Erbium co‐doped TiO₂/Ag catalysts are synthesized by using a simple, one‐step solvothermal method and characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy, Raman analysis, X‐ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. The catalysts exhibit anatase crystal structures with increased visible light absorption compared with pure TiO₂. Enhanced photocatalytic activity is observed with Er co‐doped TiO₂/Ag nanocomposites for Rhodamine B degradation under visible light irradiation. The photocatalytic activity of 1 % Er co‐doped TiO₂/Ag is much higher than that of TiO₂/Ag, TiO₂/Er, pure TiO₂, and commercial Degussa P25. The kinetics of the degradation process are studied and the pseudo‐first‐order rate constant (k) and half‐life time (t_1/2) of the reaction are calculated. The enhanced activity might be accredited to the efficient separation of electron–hole pairs by silver and higher visible light absorption of TiO₂ induced by Er.     

Review on Undoped/Doped TiO2 Nanomaterial; Synthesis and Photocatalytic and Antimicrobial Activity

This review covers the various synthetic methods of doped and undoped TiO₂ nanomaterials, ranging from single‐doped and co‐doped to multidoped with transition‐metal ions, rare earth metal ions, and other metals and nonmetals ions. The effects of doping on the physiochemical propertiesas well as the photocatalytic and antimicrobial activities of TiO₂ nanomaterial are discussed. The results from the literature show that doping of TiO₂ shifts the absorption edge to the visible region as a result of the decrease in the bandgap due to the formation of new energy levels in the bandgap. The dopent also acts as a trapping center for electrons and holes, thereby reducing the recombination rate of charge carriers and increasing the photocatalytic and antimicrobial activity of TiO₂ nanomaterials. All multidoped TiO₂ nanomaterials show higher activity than their undoped, single‐doped, and co‐doped counterparts.     

Preparation of Cr‐doped TiO2/SiO2 Photocatalysts and their Photocatalytic Properties

Cr‐doped TiO₂/SiO₂ nanostructured materials were prepared employing a layer‐by‐layer assemblym technique. TiO₂ colloids were synthesized by a sol‐gel method using TiCl₄ as a precursor. The experimental results showed that sphere‐type TiO₂ particles on SiO₂ exhibited uniform shape and a narrow size distribution. The amount of Ti (wt %) increased as a function of the number of the coating layers. The coatingv layers was composed of anatase titania nanocrystals at 550 °C. The onset of band‐gap transition for Crdoped TiO₂/SiO₂ showed a red shift compared with that for the undoped TiO₂/SiO₂. And the photocatalytic activity of Cr‐doped TiO₂/SiO₂ was higher than that of undoped sample.     

Sol-gel preparation and characterization of Co/TiO<Subscript>2</Subscript> nanoparticles: Application to the degradation of methyl orange

Cobalt doped titania nanoparticles were synthesized by sol-gel method using titanium(IV) isopropoxide and cobalt nitrate as precursors. X-Ray diffraction (XRD) results showed that titania and Co/TiO₂ nanoparticles only include anatase phase. The framework substitution of Co in TiO₂ nanoparticles was established by XRD, scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX) and Fourier transform infrared (FT-IR) techniques. Transmission electron microscopy (TEM) images confirmed the nanocrystalline nature of Co/TiO₂. The increase of cobalt doping enhanced “red-shift” in the UV-Vis absorption spectra. The dopant suppresses the growth of TiO₂ grains, agglomerates them and shifts the band absorption of TiO₂ from ultraviolet (UV) to visible region. The photocatalytic activity of samples was tested for degradation of methyl orange (MO) solutions. Although the photocatalytic activity of undoped TiO₂ was found to be higher than that of Co/TiO₂ under UV irradiation, the presence of 0.5% Co dopant in TiO₂ resulted in a catalyst with the highest activity under visible irradiation.     

Enhanced photocatalytic activity for titanium dioxide by co-modification with copper and iron

A copper(II) and iron(III) co-modified titanium dioxide nano material was prepared by a simple sol–gel process using titanium(IV) isopropoxide plus copper(II) and iron(III) nitrates as raw materials. The as-prepared nanocomposites were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy and photoluminescence spectra. The XRD results showed that the undoped TiO₂ nanoparticles mainly include anatase phase while the Cu, Fe-codoped TiO₂ nanoparticles showed a mixture of anatase phase with a small fraction of rutile phase displaying higher activity than the pure anatase phase. Optical characterization showed that the codoping with copper(II) and iron(III) resulted in a red shift of adsorption and lower recombination probability between electrons and holes, which were associated with high photocatalytic activity of the Cu, Fe-codoped TiO₂ nanoparticles under visible light (λ > 400 nm). The photocatalytic activity of the samples was tested by aqueous methyl orange degradation. The capability of the codoped catalyst was much higher than that of the pure TiO₂ catalyst under visible irradiation. A mechanism is proposed in order to account for the enhanced catalytic activity.     

The Influence of Defects on Mo‐Doped TiO2 by First‐Principles Studies

TiO₂ doped with transition metals shows improved photocatalytic efficiency. Herein the electronic and optical properties of Mo‐doped TiO₂ with defects are investigated by DFT calculations. For both rutile and anatase phases of TiO₂, the bandgap decreases continuously with increasing Mo doping level. The 4d electrons of Mo introduce localized states into the forbidden band of TiO₂, and this shifts the absorption edge into the visible‐light region and enhances the photocatalytic activity. Since defects are universally distributed in TiO₂ or doped TiO₂, the effect of oxygen deficiency due to oxygen vacancies or interstitial Mo atoms is systemically studied. Oxygen vacancies associated with the Mo dopant atoms or interstitial Mo will reduce the spin polarization and magnetic moment of Mo‐doped TiO₂. Moreover, oxygen deficiency has a negative impact on the improved photocatalytic activity of Mo‐doped TiO₂. The current results indicate that substitutional Mo, interstitial Mo, and oxygen vacancy have different impacts on the electronic/optical properties of TiO₂ and are suited to different applications.     

Tuning the Surface Structure of Nitrogen‐Doped TiO2 Nanofibres—An Effective Method to Enhance Photocatalytic Activities of Visible‐Light‐Driven Green Synthesis and Degradation

Nitrogen‐doped TiO₂ nanofibres of anatase and TiO₂(B) phases were synthesised by a reaction between titanate nanofibres of a layered structure and gaseous NH₃ at 400–700 °C, following a different mechanism than that for the direct nitrogen doping from TiO₂. The surface of the N‐doped TiO₂ nanofibres can be tuned by facial calcination in air to remove the surface‐bonded N species, whereas the core remains N doped. N‐Doped TiO₂ nanofibres, only after calcination in air, became effective photocatalysts for the decomposition of sulforhodamine B under visible‐light irradiation. The surface‐oxidised surface layer was proven to be very effective for organic molecule adsorption, and the activation of oxygen molecules, whereas the remaining N‐doped interior of the fibres strongly absorbed visible light, resulting in the generation of electrons and holes. The N‐doped nanofibres were also used as supports of gold nanoparticle (Au NP) photocatalysts for visible‐light‐driven hydroamination of phenylacetylene with aniline. Phenylacetylene was activated on the N‐doped surface of the nanofibres and aniline on the Au NPs. The Au NPs adsorbed on N‐doped TiO₂(B) nanofibres exhibited much better conversion (80 % of phenylacetylene) than when adsorbed on undoped fibres (46 %) at 40 °C and 95 % of the product is the desired imine. The surface N species can prevent the adsorption of O₂ that is unfavourable for the hydroamination reaction, and thus, improve the photocatalytic activity. Removal of the surface N species resulted in a sharp decrease of the photocatalytic activity. These photocatalysts are feasible for practical applications, because they can be easily dispersed into solution and separated from a liquid by filtration, sedimentation or centrifugation due to their fibril morphology.     

Synthesis and Modification of Zn‐doped TiO2 Nanoparticles for the Photocatalytic Degradation of Tetracycline

The synthesis of Zn‐doped TiO₂ nanoparticles by solgel method was investigated in this study, as well as its modification by H₂O₂. The catalyst was characterized by transmission electron microscopy, X‐ray diffraction, Brunauer–Emmett–Teller, UV–visible reflectance spectra and X‐ray photoelectron spectroscopy (XPS). The results indicated that doping Zn into TiO₂ nanoparticles could inhibit the transformation from anatase phase to rutile phase. Zn existed as the second valence oxidation state in the Zn‐doped TiO₂. Zn‐doped TiO₂ that was synthesized by 5% Zn doping at 450°C exhibited the best photocatalytic activity. Then, the H₂O₂ modification further enhanced the photocatalytic activity. Zn doping and H₂O₂ modifying narrowed the band gap and efficiently increased the optical absorption in visible region. The optimal degradation rate of tetracycline by Zn‐doped TiO₂ and H₂O₂ modified Zn‐doped TiO₂ was 85.27% and 88.14%. Peroxide groups were detected in XPS analysis of H₂O₂ modified Zn‐doped TiO₂, favoring the adsorption of visible light. Furthermore, Zn‐doped TiO₂ modified by H₂O₂ had relatively good reusability, exhibiting a potential practical application for tetracycline's photocatalytic degradation.