Bi3+/Ce3+ doped ZnO nanoparticles with enhanced photocatalytic and dielectric properties

In this study, varying % Bi-doped on 1% Ce-doped ZnO (1CZ) nanoparticles (X% B-1CZ) were synthesized via a facile, simple, low-cost, sol–gel process. Various characterization techniques were employed to characterize the synthesized compound, while the dielectric properties i.e. dielectric constant, dielectric loss and AC conductivity against frequency were studied with the help of a precision impedance analyzer. It was observed that by increasing bismuth content in the nanoparticles, the dielectric constant also increased in the range (1.47 × 10⁶ – 4.02 × 10⁶) at 20 Hz, and vice versa for dielectric loss decreased from 1.05 × 10⁶ to 0.39 × 10⁶. The role of prepared compounds as photocatalysts was also investigated against methylene blue under ultraviolet irradiation. The degradation efficiency, as well as the dielectric properties of 7% Bi-doped on 1% Ce-doped ZnO (7%B-1CZ), were found to be the best. Overall, it was found that the synthesized compounds proved promising candidates with enhanced photocatalytic & dielectric properties and hence could safely be employed for environmental remediation purposes and energy storage devices.     

BiVO4/TiO2 core-shell heterostructure: wide range optical absorption and enhanced photoelectrochemical and photocatalytic performance

In the present study, pristine BiVO₄, TiO₂ and BiVO₄/TiO₂ core-shell heterostructured nanoparticles are prepared by hydrothermal methods and studied for structural, morphological, optical, photoelectrochemical water splitting and photocatalytic degradation of methylene blue as an organic pollutant. Both pristine BiVO₄ and TiO₂ exhibit poor PEC and PC performance under visible light illumination. However, an enhanced PEC and PC activity in BiVO₄/TiO₂ core-shell heterostructure is observed due to high solar energy absorption and superior charge separation properties in core-shell nanoparticles. The photoelectrode prepared using BiVO₄/TiO₂ core-shell nanoparticles exhibit a photocathode behavior and produced cathodic photocurrent, however, the pristine BiVO₄ and TiO₂ photoelectrodes act as photoanode and produced anodic photocurrent. This behavior of change in current direction is also observe in the Mott-Schottky analysis where the BiVO₄/TiO₂ core-shell nanoparticles photoelectrode exhibits the positive slow showing p-type semiconducting behavior. The change in cathodic photoresponse in core-shell nanoparticles in comparison to anodic photoresponse of BiVO₄ and TiO₂ nanoparticles is explained in terms of the variations in the work function values. These results highlight the advantages of core-shell nanoparticle of suitable materials for photocatalytic and photoelectrochemical applications.     

Preparation of magnetic Fe3O4/TiO2/Ag composite microspheres with enhanced photocatalytic activity

The novel three-component Fe₃O₄/TiO₂/Ag composite mircospheres were prepared via a facile chemical deposition route. The Fe₃O₄/TiO₂ mircospheres were first prepared by the solvothermal method, and then Ag nanoparticles were anchored onto the out-layer of TiO₂ by the tyrosine-reduced method. The as-prepared magnetic Fe₃O₄/TiO₂/Ag composite mircospheres were applied as photocatalysis for the photocatalytic degradation of methylene blue. The results indicate that the photocatalytic activity of Fe₃O₄/TiO₂/Ag composite microspheres is superior to that of Fe₃O₄/TiO₂ due to the dual effects of the enhanced light absorption and reduction of photoelectron–hole pair recombination in TiO₂ with the introduction of Ag NPs. Moreover, these magnetic Fe₃O₄/TiO₂/Ag composite microspheres can be completely removed from the dispersion with the help of magnetic separation and reused with little or no loss of catalytic activity.     

Solgel-hydrothermal synthesis of Tb/Tourmaline/TiO2 nano tubes and enhanced photocatalytic activity

In this study, we synthesized Tb/Tourmaline/TiO₂ nano tubes (NTs) through a solgel-hydrothermal method. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectromicroscope, scanning electron microscopy, transmission electron microscopy and UV-vis diffuse reflectance spectroscopy. The resulting Tb/Tourmaline/TiO₂ NTs exhibited higher photocatalytic activity than pure TiO₂ and TiO₂ nano particles (NPs) in the degradation of menthyl orange under UV-light. Results revealed that doping rare earth element Tb could narrow the wide band gap of TiO₂ and tourmaline could trap the photogenerated electron of TiO₂ to inhibit the recombination of photogenerated electron-hole pairs.     

Facile synthesis of C-decorated Fe,N co-doped TiO2 with enhanced visible-light photocatalytic activity by a novel co-precursor method

Lattice-doping and surface decoration are prospective routes to improve the visible-light photocatalytic ability of TiO₂, but the two techniques are difficult to combine into one preparation process because they are usually conducted under different conditions, which limits the efficiency of TiO₂ modification. In this study, TiO₂ was successfully modified by simultaneous lattice-doping and surface decoration, and the visible-light photocatalytic capacity was largely improved. Upon comparing the method reported here with previous ones, the most significant difference is that Fe(II)-phenanthroline was first used as the co-precursor of the introduced elements of C, N, and Fe. These three elements were simultaneously introduced to TiO₂ at high levels by this co-precursor method. The as-synthesized photocatalysts were systemically investigated and analyzed by several characterization methods such as XRD, FT-IR, XPS, Raman spectroscopy, EPR, UV-Vis DRS, photoluminescence spectra, photocurrent, electrochemical impedance spectra, TEM, and HRTEM. The photocatalytic degradation of 4-NP under visible-light irradiation was used to evaluate the photocatalytic activity of the photocatalysts. Based on the experimental data, a probable mechanism for the photocatalytic degradation by the photocatalysts is proposed. This is a novel method of using one source to simultaneously introduce metal and non-metal elements to TiO₂ at high levels, which may provide a new way to prepare highly effective TiO₂ photocatalysts.     

BiOCl nanostructures with different morphologies: Tunable synthesis and visible-light-driven photocatalytic properties

BiOCl nanostructures including microspheres,microflowers,microplates,and nanoplates,have been synthesized by a simple solvothermal method using bismuth nitrate and sodium chloride as raw materials without adding any additives.Structure and morphology of the products were characterized by powder X-ray diffraction,scanning electron microscopy,and transmission electron microscopy.The results indicated that the as-prepared microspheres and microflowers were composed of nanosheets.Although with different shape and lateral size,the nanoplates and microplales were all single-crystalline plates with exposed {001) facets.It was found that the volume ratio of polyethylene glycol 400 and H₂O in the solvent played a key role in the morphology of the products,and the possible growth mechanism was also discussed.The photocatalytic measurements indicated that the BiOCl samples exhibit good photocatalytic properties towards Rhodamine B.     

BiOI@La(OH)3纳米棒异质结制备及其增强可见光催化去除NO性能

一维La(OH)3纳米棒具有特殊的电子结构和多功能特性,特别是作为半导体光催化剂引起了人们极大的兴趣.但La(OH)3禁带宽度较大,且只能吸收紫外光,所以光催化效率较低,可见光利用能力较差,限制了La(OH)3的实际应用.因此,需要开发一种高效的改进方法来提高La(OH)3的可见光催化性能.本课题组发展了一种有效的改进La(OH)3方法,通过简易的方法将BiOI纳米颗粒沉积在La(OH)3纳米棒上,有效增强了对可见光的吸收能力和光生载流子的分离能力.本文采用X射线衍射(XRD)、透射电镜(TEM)、扫描电镜(SEM)、紫外-可见漫反射光谱(UV-Vis DRS)、荧光光谱(PL)、光电子能谱(XPS)、电子自旋共振(ESR)、N2吸附和元素分析等手段研究了BiOI@La(OH)3纳米棒异质结的构建原理及增强可见光催化性能的原因.XRD和XPS结果表明,通过简易化学沉积法原位构建了BiOI@La(OH)3异质结,并且在异质结中没有杂相生成.由SEM图像可见,原始La(OH)3由分散的一维纳米棒组成,平均直径为30–50 nm.通过BiOI与La(OH)3表面的紧密接触成功构建异质结,但BiOI纳米颗粒未改变La(OH)3纳米棒的形貌.由TEM和HRTEM图像可见,La(OH)3纳米棒的平均长度为30–50 nm,并且在BiOI@La(OH)3异质结中可以清晰看出BiOI和La(OH)3之间紧密接触的界面和晶格间距.N2物理吸附结果显示,随着BiOI量的增加,BiOI@La(OH)3异质结的比表面积增加,但孔体积未现明显变化.UV-Vis DRS结果显示,引入BiOI后明显促进了La(OH)3对可见光的吸收能力和利用效率,从而有利于增强可见光催化活性.通过理论计算分别得到BiOI和La(OH)3的价带和导带位置,表明具有非常匹配的能带结构可以促进BiOI光生电子的有效转移.可见光催化去除NO测试结果表明,BiOI@La(OH)3异质结的光催化活性高达50.5%,明显优于BiOI和La(OH)3.ESR测试结果显示,BiOI@La(OH)3异质结可见光催化活性中起主要作用的活性物种是?OH.结合表征结果,BiOI@La(OH)3纳米棒异质结可见光催化性能增强的原因主要有三个:(1)BiOI@La(OH)3异质结增大的比表面积有利于反应物和产物在催化剂表面扩散,同时可提供更多活性位点参与光催化反应;(2)禁带宽度影响光催化效率,当BiOI与La(OH)3达到合适比例时,既可以促进可见光吸收,也可以使光生电子具有较强还原能力;(3)BiOI@La(OH)3异质结有利于光生载流子的分离,从而显著提高其光催化活性.     

具有高光催化活性的介孔单晶TiO2薄膜的制备

光催化技术在常温下能够直接利用太阳能来驱动反应, 已成为一种理想的环境污染治理和洁净能源生产技术. 但是比较多的限制条件阻碍了光催化发展和实际应用, 如何有效解决这些限制因素成为光催化技术走向工业化应用必须解决的问题. 目前光催化材料研究存在的问题主要包括: (1)研究工作主要集中的粉体催化剂存在分离困难、难以重复利用的缺点, 开发与基底结合牢固的薄膜材料是十分必要的; (2)光催化材料本身的光响应范围影响光催化材料的应用, 拓宽催化剂材料的光吸收范围是亟待解决的; (3)光生电子和空穴的复合问题是影响光催化剂催化活性的主要因素之一, 很多方法被用来阻止电子-空穴对的复合, 如: 金属和非金属的掺杂、贵金属修饰、异质结、新型催化剂结构的设计等, 如何设计促进催化剂光生电子和空穴的分离成为光催化技术应用的重要问题.介孔单晶TiO2通过自组装的方法被制备, 成为TiO2的一种新结构材料. 介孔单晶TiO2结合了介孔材料的大比表面积、单晶材料的电荷传输快等优点, 对于光催化性能有了很大的提高. 目前介孔单晶TiO2主要是以粉体的形式存在, 但是粉体TiO2的应用受到多方面的影响, 如: 难回收不易重复利用, 与电催化结合难, 不能借助电催化提高电荷分离效率等. TiO2薄膜能够解决粉体的不足, 近年来, TiO2光催化薄膜得到广泛的研究, TiO2薄膜的制备方法很多, 主要有液相制备方法、物理气相沉积法、化学气相沉积法、电化学方法、溅射法等. TiO2薄膜主要是以纳米颗粒的形式沉积在基底上, 并且多为多晶和无定形. 而对于介孔单晶TiO2薄膜的制备和研究还没有报道. 我们通过直接焙烧一步法制备了介孔单晶TiO2薄膜, 并对TiO2薄膜的生长情况、表面结构、TiO2晶相和晶体完整程度的变化对性能的影响进行了研究. 通过调变Ti与F的比例和煅烧温度, 研究不同的制备条件对其性能的影响, 从而制备高活性TiO2薄膜. 为了进一步提高介孔单晶TiO2薄膜的活性和拓展其吸收光谱范围, 使用高温热解自组装技术一步法制备了贵金属Au负载的介孔单价TiO2薄膜, Au纳米颗粒跟TiO2有较好的结合度. 在可见光照射下, Au/TiO2异质结构中Au表面由等离子体共振效应产生的活泼电子会注入TiO2导带, 使光生电子和空穴得到分离; 同时Au具有特殊的可见光等离子体共振效应能显著改善TiO2类宽带隙半导体的可见光响应性能.实验用还原Cr(Ⅵ)作为探针反应, 考察不同Au含量对光催化性能的影响.     

Preparation and optical properties of three-dimensional navel-like Bi2WO6 hierarchical microspheres

Three-dimensional (3D) navel-like Bi₂WO₆ hierarchical microspheres were successfully prepared using a simple hydrothermal method. The 3D navel-like BWO hierarchical structure composed of well-ordered nanosheets displayed the excellent photocatalytic activity, and the degradation rate of norfloxacin was about 67%.     

Preparation of carbon nitride nanoparticles by nanoprecipitation method with high yield and enhanced photocatalytic activity

As an emerging 2D conjugated material,graphitic carbon nitride(CN) has attracted great research attention as important catalytic medium for transforming solar energy.Nanostructure modulation of CN is an effective way to improve catalytic activities and has been extensively investigated,but remains challenging due to complex processes,time consuming or low yield.Here,taking advantage of recent discovered good solvents for CN,a nanoprecipitation approach using poor solvents is proposed for preparation of CN nanoparticles(CN NPs).With simple processes of CN dissolution and precipitation,we can quickly synthesize CN NPs(^40 nm) with a yield of up to 50%,the highest one to the best of our knowledge.As an example of potential applications,the as-prepared CN NPs were applied to photocatalytic degradation of dyes with an evident boosted performance up to 2.5 times.This work would open a new way for batch preparation of nanostructured CN and pave its large-scale industrial applications.     

具有高光催化活性的黑色TiO2（B）/锐钛矿双晶TiO2-x纳米纤维

高效TiO2基光催化材料的开发一直是催化领域的研究热点,主要的策略是如何有效地分离光生载流子.制备多晶相的TiO2材料可引入异质/相结结构使电子与空穴朝不同方向移动,从而避免电子与空穴复合;另外,在TiO2中掺杂其他金属或非金属也可以有效地降低电子与空穴的复合率,掺杂的元素作为电子捕获阱俘获光生电子,以实现电子空穴的有效分离.近些年,作为一种全新的掺杂剂,氧空穴可以有效改善TiO2的光催化活性,所制TiO2具有可见光的全光谱吸收能力,因此该类TiO2呈现出黑色.通过上述方法均可以制备出高活性TiO2基光催化材料,如果能够将这些方法耦合一起,则可能制备出活性更高的光催化剂.因此,本文将异相结结构和空穴掺杂耦合起来,用多孔钛酸盐衍生物在H2中高温焙烧制得一种全新的黑色TiO2(B)/锐钛矿双晶TiO2–x纳米纤维.不同于其他TiO2基光催化材料,该样品仅由Ti和O元素组成,通过Ti和O元素的组合,形成了双晶结构和空穴掺杂两种特殊的结构,借助场发射(FESEM)、拉曼光谱(Raman)、氮气物理吸脱附、X射线光电子能谱(XPS)、热重(TG)、紫外可见漫反射光谱(UV-Vis)和荧光光谱(PL)等表征分析了样品的结构及其光催化性能间构效关系. FESEM结果显示,黑色TiO2(B)/锐钛矿双晶TiO2–x为长1–5mm、宽0.2mm的纤维结构, Raman结果表明,锐钛矿相在特征波段(140 cm–1左右)和TiO2(B)的特征波段(220–260 cm–1)均发生蓝移,说明该两相中均存在氧空穴;该样表面未检测到Ti3+,因此氧空穴可能分散在TiO2(B)和锐钛矿相的体相中.根据黑色TiO2(B)/锐钛矿双晶TiO2–x和白色TiO2(B)/锐钛矿双晶TiO2的失重差,估算出前者的O/Ti原子比为1.97.光催化降解甲基橙实验结果显示,黑色TiO2(B)/锐钛矿双晶TiO2–x的光催化活性是白色双晶TiO2的4.2倍,锐钛矿TiO2的10.5倍,且连续反应10次后未出现失活现象,显示出了良好的光催化稳定性.前期,我们已经证明了白色TiO2(B)/锐钛矿双晶TiO2由于具有TiO2(B)和锐钛矿的异相结结构,致使其电子空穴有效地分离,从而表现出优异的光催化活性;本文的PL结果显示,由于氧空穴的引入,异相结与氧空穴两者共同作用,进一步促进了黑色TiO2(B)/锐钛矿双晶TiO2–x电子与空穴的有效分离,因此黑色TiO2(B)/锐钛矿双晶TiO2–x表现出高的光催化活性.由于其特殊的结构,黑色TiO2(B)/锐钛矿双晶TiO2–x纳米纤维将在环境与能源领域表现出良好的应用前景.     

Surfactant assisted hydrothermal synthesis of SnO nanoparticles with enhanced photocatalytic activity

SnO nanoparticles have been successfully synthesized in the presence of Triton-X 100 (TX-100) surfactant via hydrothermal method for the first time, and the photocatalytic activity under UV and visible light irradiation for the degradation of Methylene Blue (MB) and Rhodamine B (RdB) organic textile dyes was investigated. The structural, morphological and chemical characterizations were investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), UV–vis. diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence (PL) analysis. The results reveal that the addition of surfactant, TX-100, in the precursor solutions leads to reduction in crystallite size with significant changes in morphological structure of SnO nanoparticles. The synthesized SnO nanoparticles show excellent photocatalytic activity under UV or visible light irradiation. MB and RdB dyes degraded completely under UV irradiation after 90 and 150 min, respectively. Also, MB and RdB dyes degraded only 150 min later under visible light illumination with a little amount of photocatalyst (0.8 g/L). Hence, this work explores the facile route to synthesizing efficient SnO nanoparticles for degrading organic compound under both UV and visible light irradiations.     

Novel titanate nanotubes-cyanocobalamin materials: Synthesis and enhanced photocatalytic properties for pollutants removal

New hybrid nanomaterials, with improved photocatalytic performance in pollutants removal, were obtained through the modification of titanate nanotubes (TNT) with a cobalt porphyrin, the cyanocobalamin, also knowing as vitamin B12 (B12). The nanocrystalline TNT were produced by hydrothermal treatment and after treated with cobalamin to produce B12-TNT materials. The characterization of the new hybrid material was performed by XRD, FTIR, TEM-EDS, DRS, XPS and ICP. The results show that the immobilization of the cobalt containing specie is dependent on the point of zero charge of the TNT and no modifications on the structure and morphology were observed. No significant changes in the optical band gap were observed after B12 incorporation, but an increasing in the visible light absorption, which arises from charge transfer and d–d transitions of the cobalt, was visualized. The samples photocatalytic performance was studied for the hydroxyl radical production and the highest catalytic ability was achieved by the B12-HTNT sample. The catalytic ability of these new hybrid nanomaterials for two model pollutants photodegradation, phenol and rhodamine B (RhB) was investigated. For both pollutants, the best results were achieved using B12-HTNT with a removal of 94% of a 10 ppm RhB and 87% of a 20 ppm phenol solution in 90 min of irradiation (150 mL, 0.2 g catalyst/L).     

离子刻蚀法制备具有高效催化性能的m-Bi2O4/BiOCl p-n异质结催化剂

光催化技术作为一种绿色的环境修复方法而备受关注,它直接利用太阳光作为能源,可有效地降解有机污染物.铋系化合物具有化学稳定性强、抑制光腐蚀、无毒和来源广泛等优点,被认为是一种环境友好的光催化剂,广泛用于降解染料、苯酚和其他有机污染物.BiOCl具有独特的内部结构,可形成内电场促进电子和空穴的移动,抑制其复合.但是BiOCl本身带隙能过大,只能被紫外光激发,对光的利用率较低,限制了其在环境治理中的应用.近两年来发现,m-Bi2O4带隙能小,可吸收大波长的可见光,催化性能好.为充分发挥m-Bi2O4的优异性质,改善BiOCl的性能,本文将BiOCl与m-Bi2O4复合制得新型催化剂,降低催化剂的带隙能,增强对光的吸收,提高量子效率,促进光生载流子的分离,抑制电子-空穴复合,从而提高催化剂性能,加速降解反应进程.本文通过离子刻蚀法制备具有p-n异质结的m-Bi2O4/BiOCl复合催化剂,通过调节HCl的加入量制得不同比例的催化剂,并考察了其在可见光下催化降解MO(甲基橙)的性能.结果表明,m-Bi2O4/BiOCl复合催化剂在可见光下表现出优异的光催化降解MO和四环素的性能,反应10内min可降解95％的MO,反应150 min内四环素的降解率为85.5％;该复合催化剂对MO和四环素的光降解效率分别是纯BiOCl的52.3和4.9倍.活性自由基捕获实验表明,空穴在光催化降解过程中起最主要的作用,其次是超氧自由基,羟基自由基对降解反应也起到一定的作用.采用XRD,SEM,EDS,TEM,SAED,FT-IR,Raman,XPS,BET,UV-vis和光电流等表征方法分析了催化剂的结构、形貌、化学组成、元素价态、孔结构、带隙能、光学性质和载流子复合效率.结果表明,与BiOCl的斜四方体相比,m-Bi2O4/BiOCl复合催化剂呈现纳米片状结构,氯离子进入晶格的内部,颜色也由BiOCl原来的深褐色变为黄色.m-Bi2O4/BiOCl为介孔结构,比表面积为112.90 m2/g,其吸收波长红移,由紫外光扩展至可见光区域,带隙能也由3.2降低为1.87 eV,能带弯曲形成p-n异质结,提高了电子-空穴的转移效率,抑制其复合;m-Bi2O4/BiOCl的光电流密度高于m-Bi2O4和BiOCl,电子-空穴的分离效率更高,因而其催化性能更优越.     

Novel CaCO3/g-C3N4 composites with enhanced charge separation and photocatalytic activity

A novel CaCO₃/graphitic carbon nitride (g-C₃N₄) photocatalyst was synthesized for the first time via a facile calcination method using CaCO₃ and melamine as precursors. The as-prepared samples were characterized using various techniques, such as scanning and transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller analysis, as well as Fourier-transform infrared, X-ray photoelectron, photoluminescence, and UV–vis diffuse reflectance spectroscopy. The results of the experiments confirm the successful coupling of CaCO₃ to g-C₃N₄. The photocatalytic activity of the synthesized CaCO₃/g-C₃N₄ composites was evaluated by assessing their performance in the photocatalytic degradation of crystal violet (CV) in water under visible light irradiation. The analysis shows that CaCO₃/g-C₃N₄ exhibits higher photocatalytic activity towards CV degradation (76.0%) than pristine g-C₃N₄ (21.6%) and CaCO₃ (23.2%). Radical trapping and electron spin resonance experiments show that hydroxyl radicals (OH) and holes (h⁺) are the key reactive species in the photocatalytic process. The enhanced photocatalytic activity of the composite is mainly attributed to the efficient separation rate of electron-hole pairs achieved through the incorporation of CaCO₃.     

盐酸溶液处理钒酸铋增强可见光催化活性及其机理

采用盐酸水溶液处理BiVO₄ 的方法获得增强的光催化活性. 在0.1 mol·L^-1 酸溶液中浸渍反应6 h,BiVO₄ 的可见光催化降解苯酚的活性提高了3.5 倍. 采用X 射线衍射(XRD), 扫描电镜(TEM)和漫反射光谱(DRS)等表征手段研究处理后样品的晶相组成和表面形貌, 结合不同酸和氯化物处理的对照实验, 结果表明,在H⁺和Cl^-的协同作用下, BiVO₄表面部分溶出并以BiOCl 沉积, 形成了表面具有凹陷沟壑的BiVO₄颗粒与片状结构BiOCl 的复合物. 采用悬浮液光电压法测定BiOCl 平带电位, 通过BiVO₄和BiOCl 的能带分析及其混合颗粒的光催化活性测试, 确证二者间不存在颗粒间电子转移效应. 增强的光催化活性主要归因于BiVO₄表面形成了有助于光生电荷迁移的凹凸不平结构. 这种表面处理方法有望成为一种增强半导体化合物光催化活性的有效途径.     

Synthesis and photocatalytic activity for water-splitting reaction of nanocrystalline mesoporous titania prepared by hydrothermal method

Nanocrystalline mesoporous TiO₂ was synthesized by hydrothermal method using titanium butoxide as starting material. XRD, SEM, and TEM analyses revealed that the synthesized TiO₂ had anatase structure with crystalline size of about 8 nm. Moreover, the synthesized titania possessed a narrow pore size distribution with average pore diameter and high specific surface area of 215 m²/g. The photocatalytic activity of synthesized TiO₂ was evaluated with photocatalytic H₂ production from water-splitting reaction. The photocatalytic activity of synthesized TiO₂ treated with appropriate calcination temperature was considerably higher than that of commercial TiO₂ (Ishihara ST-01). The utilization of mesoporous TiO₂ photocatalyst with high crystallinity of anatase phase promoted great H₂ production. Furthermore, the reaction temperature significantly influences the water-splitting reaction.     

Hydrothermal synthesis and enhanced photocatalytic activity of mixed-phase TiO2 powders with controllable anatase/rutile ratio

In this study, mixed-phase TiO₂ powders were novelly synthesized via a facile and mild hydrothermal method without any post-heat treatment. TiOSO₄ and peroxide titanic acid (PTA) were used as inorganic titanium sources, while no special solvent or additive were introduced. The XRD and TEM results showed the mixed-phase TiO₂ powders were composed of anatase and rutile phases, and the PTA sol played an important role on forming the rutile nucleus. The proportion of rutile in the mixed-phase TiO₂ could be easily controlled in the range of 0%–70.5% by changing the amount of PTA sol used in the synthesis process. The UV-Visible absorption spectra indicated the prepared mixed-phase TiO₂ showed enhanced visible light absorption with the increase of rutile ratio. The photodegradation experiments revealed the mixed-phase TiO₂ exhibited the best photocatalytic activity at the rutile ratio of 41.5%, while a higher or lower rutile ratio both resulted in the decrease of photocatalytic activity.     

Fabrication of niobium doped titanate nanoflakes with enhanced visible-light-driven photocatalytic activity for efficient ibuprofen degradation

Niobium doping increases the visible light adsorption of titanate nanoflakes, which greatly enhances the photocatalytic activity for ibuprofen elimination.     

原位制备具有增强光催化活性的S型Bi2Se3/g-C3N4光催化剂

光催化氧化是一种应用前景良好的环境治理技术.与絮凝、物理吸附和化学氧化等常见的方法相比,光催化氧化具有环境友好、氧化完全、方便和廉价等优势.特别是可见光光催化氧化,可利用太阳能中占比最高的可见光,在应用中更具优势.因而,探索可见光响应性能优异的光催化剂一直是光催化氧化领域的一个重要研究内容.硒化铋(Bi₂Se₃)是一种带隙(带隙宽度在0.3~1.3 e V)非常窄的半导体,能吸收全部波长范围的可见光和近红外光.此外,Bi₂Se₃还具有独特的金属表面态,其表面具有良好的导电性.这些特性使其在可见光光催化氧化领域具有很大的应用潜力.然而,由于Bi₂Se₃价带位置高,氧化能力很弱,其价带上的空穴在光催化反应中难以被消耗,导致空穴大量累积,并迅速与光生电子复合,大幅降低了Bi₂Se₃的光催化性能.因此,一直以来,Bi₂Se₃很少被用于光催化反应.如何充分利用Bi₂Se₃的光响应优势,制备出性能优异的光催化剂,仍是具有挑战性和吸引力的研究方向.本文采用预先制备的Bi2O3/g-C₃N₄复合物作为前驱体,通过原位转化的方法,将前驱体置于热的Se蒸汽中,使前驱体上的Bi2O3与Se蒸汽反应,完全转化为Bi₂Se₃纳米颗粒,从而制得Bi₂Se₃/g-C₃N₄复合光催化剂(Bi₂Se₃含量约为4 wt%).透射电镜结果表明,所形成的Bi₂Se₃纳米颗粒较均匀地分布在g-C₃N₄表面.表面功函数分析发现,Bi₂Se₃与g-C₃N₄结合后,它们的费米能级分别由原来的-0.55和-0.18 e V变为平衡时的-0.22 e V,可形成指向g-C₃N₄的内建电场,有利于形成梯型(S型)异质结.在此基础上,能级位移、荧光分析、结构计算和反应自由基测试等结果表明,Bi₂Se₃和g-C₃N₄之间形成了S型异质结.在可见光光催化降解苯酚的实验中,所制备的Bi₂Se₃/g-C₃N₄复合物的光催化活性明显优于单一的Bi₂Se₃和g-C₃N₄.结合比表面、孔结构、光吸收和荧光等对比分析,认为Bi₂Se₃/g-C₃N₄的这种S型异质结构在其光催化活性增强中起到了关键作用.在光照条件下,其g-C₃N₄导带中光生电子向Bi₂Se₃的价带迁移,并与光生空穴复合,从而使Bi₂Se₃导带上可保留更多的高活性光生电子参与光催化反应,由此Bi₂Se₃/g-C₃N₄的光催化活性增强.循环性能测试和光还原实验结果表明,所制备的Bi₂Se₃/g-C₃N₄复合光催化剂具有良好的稳定性.本文工作为高可见光吸收的光催化剂制备和性能增强提供了新途径和新视野.