微观形貌可控TiO2的制备及其光解水产氢性能

通过简单的沉淀、水热、溶剂热和溶胶凝胶法分别制备出实心球(s-TiO_2)、空心球(h-TiO_2)、纳米管(a-TNT)和介孔形状(mTiO_2)的锐钛矿晶型结构TiO_2光催化材料。采用HRTEM、FESEM、XRD、UV-Vis、N2吸-脱附和光解水制氢反应等对催化材料的微观表面结构、光吸收性能以及不同形貌光催化剂的光解水制氢的性能对比研究。结果表明:s-TiO_2具有最高的光催化活性,主要归功于s-TiO_2独特的微观形貌结构所致,s-TiO_2是由亚微晶颗粒组成的介孔状实心球,亚微晶粒径相比较其它形貌的材料要小,有利于光生载流子的迁移,抑制电子-空穴对的体相复合,导致活性提高。同时,晶化过程用于传质通道的无序微孔可以束缚用作牺牲剂的CH3OH分子,使得空穴快速被牺牲剂消耗,减少与电子复合。     

Ag-NaTaO3-RGO复合物的合成及其改进的光催化制氢性能

以石墨粉,钽酸钠以及硝酸银为原料,通过三步合成法制备出一系列Ag-NaTaO₃-RGO复合材料。并对样品在紫外光照射下的光解水制氢活性进行了评价。结果表明：系列Ag-NaTaO₃-RGO复合材料均表现出较高的光解水制氢活性。其中,性能最优的0.2Ag-NaTaO₃-RGO的制氢速率分别是NaTaO₃,Ag-NaTaO₃,和NaTaO₃-RGO的5.64,1.97和1.48倍。对Ag-NaTaO₃-RGO复合材料光催化制氢性能改进的原因进行了探讨：（1）石墨烯具有优异的电子转移性能,能够有效阻止光生电子、空穴的复合。（2）银纳米颗粒充当电子陷阱,能够进一步提高电子空穴分离速率。（3）石墨烯的引入增强了复合物的光吸收性能。最后,根据所得实验数据,给出了Ag-NaTaO₃-RGO复合材料光催化制氢的反应机理。     

Ag-NaTaO3-RGO复合物的合成及其改进的光催化制氢性能

以石墨粉,钽酸钠以及硝酸银为原料,通过三步合成法制备出一系列Ag-NaTaO₃-RGO复合材料。并对样品在紫外光照射下的光解水制氢活性进行了评价。结果表明：系列Ag-NaTaO₃-RGO复合材料均表现出较高的光解水制氢活性。其中,性能最优的0.2Ag-NaTaO₃-RGO的制氢速率分别是NaTaO₃,Ag-NaTaO₃,和NaTaO₃-RGO的5.64,1.97和1.48倍。对Ag-NaTaO₃-RGO复合材料光催化制氢性能改进的原因进行了探讨：（1）石墨烯具有优异的电子转移性能,能够有效阻止光生电子、空穴的复合。（2）银纳米颗粒充当电子陷阱,能够进一步提高电子空穴分离速率。（3）石墨烯的引入增强了复合物的光吸收性能。最后,根据所得实验数据,给出了Ag-NaTaO₃-RGO复合材料光催化制氢的反应机理。     

中空Ta2O5/TiO2复合光催化剂的可控氧化制备及性能

以钛粉、钽粉为原料,炭黑作为反应性模板,通过熔盐法在炭黑表面原位生长了TaTiC₂纳米碳化物涂层,并以所得TaTiC₂/C复合物为碳化物前驱体,再经可控氧化制备出中空Ta₂O₅/TiO₂复合光催化剂。采用X射线粉末衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、紫外-可见（UV-Vis）漫反射（DRS）及N₂物理吸附等手段对所制备的光催化剂进行形貌、显微结构及孔结构表征。以高压汞灯为紫外光源,以亚甲基蓝为目标降解物,通过光催化降解实验评价中空Ta₂O₅/TiO₂复合光催化剂的光催化活性。结果表明,熔盐法生长碳化物涂层厚度均匀（20~30 nm）,碳化物主要以TaTiC₂晶相存在且具有纳米级的颗粒尺寸。中空Ta₂O₅/TiO₂复合光催化剂同时具有200 nm左右的中空大孔结构及壳层10 nm左右的介孔结构。中空大孔和介孔的存在提高了所制备催化剂对亚甲基蓝的吸附能力。此外,TiO₂与Ta₂O₅通过电子能带结构的耦合,有效提高了光生电子和空穴的分离效率,从而显著提高了光催化活性。n_Ti∶n_Ta=2.5∶1.5时,相应的中空Ta₂O₅/TiO₂复合光催化剂表现出最佳的光催化活性,对亚甲基蓝的紫外光催化降解率高达97%。     

异质型BiOI/NaBiO3光催化剂的合成及其光催化性能

根据表面化学蚀刻原理采用加热冷凝回流的方法制备了一系列组成的异质结构BiOI/NaBiO₃光催化剂.利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)和紫外-可见漫反射光谱(UV-Vis-DRS)等技术对其晶相结构、微观形貌和光吸收性能进行了表征.光催化实验表明,BiOI/NaBiO₃在可见光下可以有效降解罗丹明B(RhB),当BiOI与NaBiO₃的物质的量分数为一定值时,异质结构的光催化剂明显优于单一组分的光催化活性.通过加入不同的牺牲剂及荧光实验结果推测了该异质结构材料的光催化机理,并且分析了其光生载流子的传输方向及光催化过程的活性物种.研究表明,BiOI/NaBiO₃的催化活性增强主要归结为两者之间形成了有效的异质结构,其内建电场能够促进光生载流子的分离,同时光生空穴h⁺在光催化降解过程中是主要的活性物种.     

LiNbO3不同晶面的光催化产氢性能

研究了LiNbO₃（001）、（100）和（110）晶面的光催化产氢性能。（001）、（100）和（110）3个晶面光催化产氢性能之比为7.8：1.3：1.0。LiNbO₃[001]晶向存在电偶极矩和自发极化,有利于增加光生电子和空穴的分离效率,减少光生电子和空穴的复合,提高LiNbO₃（001）面的光催化活性。LiNbO₃（001）面的空穴有效质量最小,有利于光生空穴的迁移,从而减少光生电子和空穴的复合,也有利于光催化性能的提高。     

金/氧化亚铜异质球的制备及其可见光催化性能

使用L-半胱氨酸作为连接剂, 利用硼氢化钠原位还原预先吸附在介孔氧化亚铜表面的氯金酸根离子,得到了Au/Cu₂O异质结构. 应用X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱和N₂物理吸附等手段对催化剂进行表征, 并以λ>400 nm的可见光作为光源, 评价了该催化剂光催化降解亚甲基蓝(MB)的活性. 实验结果表明, 直径为4 nm的金颗粒完好地负载在介孔氧化亚铜的表面, 并且介孔氧化亚铜的细微结构与孔径均未发生变化. 研究表明, 以乙醇作为反应溶剂有效抑制了AuCl₄^-与Cu₂O之间的氧化还原反应, 从而有利于氧化亚铜介孔结构的保持及金颗粒的原位还原. 光催化降解亚甲基蓝的结果表明, Au/Cu₂O异质结构的光催化活性比纯氧化亚铜光催化活性有明显提高. 推测其光催化性能提高的主要原因如下: 一方面, 金颗粒良好的导电性有利于氧化亚铜表面电子的快速转移, 实现电子-空穴分离; 另一方面, 金颗粒可能存在的表面等离子共振现象加速了光生电子的产生.     

加热方式及原料配比对介孔CeO2结构及其光催化性能的影响

以P123（聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物）为模板剂,Ce（NO₃）₃为反应原料,通过考察加热方式、加热温度、原料配比等因素,合成了结构性能较好、表面羟基含量较高的介孔CeO₂材料。利用XRD,N₂吸附-脱附,TEM,Raman,FT-IR等技术对合成样品的结构性能进行了表征,结果表明,当P123与Ce（NO₃）₃物质的量之比为1：10,在110℃水热下合成的CeO₂结构性能最好。以酸性橙7（AO7）为探针分子,对合成介孔CeO₂的光催化性能进行评价。光催化结果证明,由于表面羟基含量较高、介孔及氧缺位的形成,所合成结构性能较好的CeO₂,利用可见光可彻底催化降解溶液中的AO7。     

微米级大孔结构二氧化钛的光催化活性

以溶胶-凝胶法合成了具有微米级大孔孔道结构的锐钛矿晶型TiO₂, 以紫外光催化降解染料罗丹明B (RhB)考察了大孔结构材料的光催化活性. 对比研磨粉碎后失去大孔结构的材料的光催化活性, 我们发现在相同的实验条件下, 大孔结构的TiO₂并不具有更好的光催化效果, 即对于本文所合成的大孔结构TiO₂, 单纯的微米级大孔的形貌对材料的光催化活性没有明显的促进作用, 而更多的TiO₂外表面受到紫外光照射是促进光催化效果的直接原因. 由于研磨后样品颗粒尺寸不均匀, 为了避免颗粒大小不均匀对光催化活性的影响, 我们又用十六烷基三甲基溴化铵(CTAB)和聚丙烯酸(PAA)为模板合成了形貌均匀尺寸不同的微球, 并证明了粒子尺寸越小催化效果越好.     

火焰辅助热解方法制备Ag2O/TiO2及其光催化制氢性能

以钛酸丁酯和硝酸银为前驱体,采用一步火焰辅助热解法制备了Ag₂O/TiO₂光催化剂并研究了样品在紫外-可见光照射下的光催化制氢性能。利用X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线光电子能谱（XPS）和紫外-可见漫反射吸收光谱（UV-Vis DRS）对样品进行了表征。XRD结果表明TiO₂均为锐钛矿晶型,Ag的引入对XRD结果无明显影响。SEM图显示未修饰的TiO₂是微球形貌,随着引入Ag含量的增加,微球减少直至消失。通过XPS分析和化学沉淀法表明样品中Ag的存在形式为Ag₂O。UV-Vis DRS测试发现引入Ag后提高了样品的光吸收。前驱体中Ag的量影响样品的光催化活性,最高的光催化制氢的活性可以达到相同条件下的P25的15倍。对光催化反应后的样品进行分析,认为在光催化过程中部分Ag₂O通过光生电子转化为Ag形成Ag/TiO₂,进一步提高光催化制氢活性。     

Gd-N共掺杂SrTiO3/TiO2复合纳米纤维制备及光催化性能

以静电纺丝技术制备的TiO_2纳米纤维为基质和反应物,结合一步水热法制得Gd-N共掺杂SrTiO_3/TiO_2复合纳米纤维光催化剂。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电镜(HRTEM)、X射线光电子能谱(XPS)、紫外-可见漫反射(UV-Vis DRS)和荧光光谱(PL)等方法对其微观结构、形貌和光学性能进行表征。结果表明:SrTiO_3和TiO_2形成异质结能够使光生电子和空穴得到很好的分离,而Gd-N共掺杂产生新带隙,可以拓宽光谱响应范围至可见光区,并引起晶格缺陷,成为光生电子-空穴对的浅势捕获阱。Gd-N共掺杂与异质结的协同作用有效提高了SrTiO_3/TiO_2复合纳米纤维的可见光催化活性。     

一种简单的提高无定形TiO2光催化活性的方法及其在增透膜中的应用

通过简单的溶胶-凝胶法制备得到了小粒径的无定形TiO_2粒子,并将其沉积在多孔SiO_2膜层表面,多孔SiO_2膜层大的表面积有助于无定形TiO_2的良好分散,高度分散的无定形TiO_2粒子对膜层的光学性能影响较小,通过匹配合适的低折射率的SiO_2膜层,制备得到的SiO_2无定形TiO_2(SiO_2amorphous-TiO_2)膜层表现出和理想单层增透膜相似的光学性能。同时SiO_2amorphous-TiO_2的光催化性能显著提高,明显高于单层无定形TiO_2。而且SiO_2无定形TiO_2膜层甚至表现出比相应的负载锐钛矿型TiO_2的膜层,即SiO_2锐钛矿TiO_2,更高的光催化活性,这一反常现象的原因是,无定型TiO_2膜层表面丰富的羟基有助于减少空穴-电子对的复合,其相对疏松的结构能够加快光生电子-空穴的转移速率,而这些因素的影响超过了晶型结构对光催化活性的影响。同时SiO_2膜层的孔隙结构在浸渍-提拉镀制过程中,自发形成并不需要后续热处理过程,因此,整个SiO_2无定形TiO_2膜层的制备均可在室温下完成,能够实现其在不耐热基片上的应用。     

Thin Heterojunctions and Spatially Separated Cocatalysts To Simultaneously Reduce Bulk and Surface Recombination in Photocatalysts

Efficient charge separation and light absorption are crucial for solar energy conversion over solid photocatalysts. This paper describes the construction of Pt@TiO₂@In₂O₃@MnO_x mesoporous hollow spheres (PTIM‐MSs) for highly efficient photocatalytic oxidation. TiO₂–In₂O₃ double‐layered shells were selectively decorated with Pt nanoparticles and MnO_x on the inner and outer surfaces, respectively. The spatially separated cocatalysts drive electrons and holes near the surface to flow in opposite directions, while the thin heterogeneous shell separates the charges generated in the bulk phase. The synergy between the thin heterojunctions and the spatially separated cocatalysts can simultaneously reduce bulk and surface/subsurface recombination. In₂O₃ also serves as a sensitizer to enhance light absorption. The PTIM‐MSs exhibit high photocatalytic activity for both water and alcohol oxidation.     

TiO2 nanoparticles incorporated with CuInS2 clusters: preparation and photocatalytic activity for degradation of 4-nitrophenol

TiO₂ nanoparticles incorporated with CuInS₂ clusters were prepared in a solvothermal process and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersion X-ray analysis (EDX). Compared with pure TiO₂ nanoparticles, the TiO₂ nanoparticles incorporated with CuInS₂ clusters display higher photocatalytic activity with 99.9% of degradation ratio of 4-nitrophenol after 2 h irradiation. In order to investigate the effect of the CuInS₂ clusters on the photocatalytic activity of TiO₂ nanoparticles, diffuse reflectance UV–Vis spectra (DRS), photoluminescence (PL) spectra, and photocurrent action spectra were measured. The results indicate that the enhanced photocatalytic activity is probably due to the interface between TiO₂ and CuInS₂ as a trap of the photogenerated electrons to decrease the recombination of electrons and holes.     

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.     

Sonochemical fabrication of fluorinated mesoporous titanium dioxide microspheres

A sonochemical-hydrothermal method for preparing fluorinated mesoporous TiO₂ microspheres was developed. Formation of mesoporous TiO₂ and doping of fluorine was achieved by sonication and then hydrothermal treatment of a solution containing titanium isopropoxide, template, and sodium fluoride. The as-synthesized TiO₂ microspheres were characterized by X-ray diffraction (XRD), Fourier translation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, photoluminescence spectroscopy (PL), and BET surface areas. The P123 template was removed completely during the hydrothermal and washing steps, which was different from the conventional calcination treatment. The as- synthesized TiO₂ microspheres had good crystallinity and high stability. Results from the photocatalytic degradation of methylene blue (MB) showed that fluorination could remarkably improve the photocatalytic activity of titanium dioxide.     

Synthesis and Photocatalytic Activity of TiO2/CdS Nanocomposites with Co-Exposed Anatase Highly Reactive Facets

In this work, TiO₂/CdS nanocomposites with co-exposed {101}/[111]-facets (NH4F-TiO2/CdS), {101}/{010} facets (FMA-TiO2/CdS), and {101}/{010}/[111]-facets (HF-TiO2/CdS and Urea-TiO2/CdS) were successfully synthesized through a one-pot solvothermal method by using [Ti₄O₉]²⁻ colloidal solution containing CdS crystals as the precursor. The crystal structure, morphology, specific surface area, pore size distribution, separation, and recombination of photogenerated electrons/holes of the TiO₂/CdS nanocomposites were characterized. The photocatalytic activity and cycling performance of the TiO₂/CdS nanocomposites were also investigated. The results showed that as-prepared FMA-TiO₂/CdS with co-exposed {101}/{010} facets exhibited the highest photocatalytic activity in the process of photocatalytic degradation of methyl orange (MO), and its degradation efficiency was 88.4%. The rate constants of FMA-TiO₂/CdS was 0.0167 min⁻¹, which was 55.7, 4.0, 3.7, 3.5, 3.3, and 1.9 times of No catalyst, CdS, HF-TiO₂/CdS, NH₄F-TiO₂/CdS, CM-TiO₂, Urea-TiO₂/CdS, respectively. The highest photocatalytic activity of FMA-TiO₂/CdS could be attributed to the synergistic effects of the largest surface energy, co-exposed {101}/{010} facets, the lowest photoluminescence intensity, lower charge-transfer resistance, and a higher charge-transfer efficiency.     

Template‐free Fabrication of ZnS/TiO2 Photocatalyst with Macrochannels

Constructing a porous structure in photocatalysts is an effective strategy for improving the photocatalytic activity because of its enhanced molecule transfer capability and light capturing efficiency. In this work, a hierarchical macro‐/mesoporous ZnS/TiO₂ composite with macrochannels was successfully synthesized without using templates by the simple dropwise addition of an ethanol solution of tetrabutyl titanate and zinc acetate into a sodium sulfide aqueous solution, which was then calcined at 450°C. Compared with pure TiO₂, the ordered porous ZnS/TiO₂ composite exhibited an enhanced photocatalytic activity on methylene blue removal under UV‐light irradiation. The results indicate that the macro‐/mesoporous structure, the large specific surface area, and the heterostructure combination between ZnS and TiO₂ play a synergistic effect on the enhanced photocatalytic activity via improving the light absorption and the diffusion of organic molecules, providing more reactive sites for the photocatalytic reaction and improving the separation of photogenerated electron–hole pairs, respectively. Radical trapping experiments demonstrated that holes (h⁺) and superoxide anion radicals (O₂⁻) play an important role in the photocatalytic oxidation process.     

Chemical synthesis of Ni/TiO<Subscript>2</Subscript> nanophotocatalyst for UV/visible light assisted degradation of organic dye in aqueous solution

The Ni/TiO₂ nanoparticles with different Ni dopant content were prepared by a modified sol–gel method. The structure and photoinduced charge properties of the as-prepared catalysts were determined using X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy techniques, and the photocatalytic efficiency of these catalysts was tested using an organic dye. It was shown that Ni modification could greatly enhance the photocatalytic efficiency of these nanocomposite catalysts by taking the photodegradation of methyl orange as a model reaction. With appropriate ratio of Ni and TiO₂, Ni/TiO₂ nanocomposites showed the superior photocatalytic activity than the single TiO₂ nanoparticles. Surface photovoltage spectra demonstrated that Ni modification could effectively inhibit the recombination of the photoinduced electron and holes of TiO₂. This electron–hole pair separation conditions are responsible for the higher photocatalytic performance of Ni/TiO₂ nanocomposites in the visible region of electromagnetic spectrum.