利用钛精矿湿化学法合成光催化纳米粉体

利用普通的钛精矿作为起始原料,联合使用浓盐酸浸出及柠檬酸凝胶燃烧法合成一种新型光催化纳米粉体。着重研究了锌离子含量和柠檬酸历肖酸摩尔比对射米粉体的微观结构及其光催化性能的影响。利用化学分析,X射线衍射,透射电子显微镜,紫外-可见漫反射吸收光谱,紫外-可见分光光度计对合成粉体的性能进行表征。通过光催化降解甲基橙溶液来评估合成粉体的光催化活性,在高压汞灯／纳米光催化粉体／双氧水体系中,光照60min后甲基橙染料的脱色率达到95％。     

Ag-ZnO/生物质炭纳米复合材料的制备及协同可见光催化性能

以醋酸锌(Zn(CH₃COO)₂·2H₂O)为锌源、硝酸银(AgNO₃)为掺杂源、纤维素纳米晶体(Cellulose nanocrystal, CNC)为生物模板，通过溶胶-凝胶法结合碳化处理，制备了Ag-ZnO/生物质炭(Biochar)复合材料。采用TEM、XRD、BET、UV-Vis DRS对所制得的Ag-ZnO/Biochar复合材料进行表征。以亚甲基蓝(MB)为模型污染物，评价Ag-ZnO/Biochar复合材料在可见光源照射下的光催化性能，进一步阐明其光催化机制。结果表明:碳化后纳米ZnO仍保持良好的分散性，球形Ag纳米粒子均匀分散在ZnO表面，形成Ag-ZnO/Biochar三元复合材料。与Ag-ZnO和ZnO/Biochar复合材料相比，Ag-ZnO/Biochar复合材料在可见光下的光催化降解率显著提高。这是由于生物质炭赋予复合体系良好的吸附性能，使MB的光催化降解反应持续发生；而Ag纳米粒子的表面等离子体共振(Surface plasmon resonance, SRP)效应则增强了复合体系在可见光区的吸收。其中，当AgNO₃、CNC、Zn(CH₃COO)₂·2H₂O的质量比为0.01:0.25:1时，制得的Ag-ZnO/Biochar复合材料在可见光下具有最佳的光吸收性能和MB降解效率:室温条件下，黑暗中吸附30 min，再用可见光照射120 min，即可达到99%的MB降解率，显著高于Ag-ZnO(约23%)和ZnO/Biochar复合材料(约64%)。      

可见光响应型Pt/GaP纳米粉体的光催化性质

利用水合肼液相还原法在纳米磷化镓(GaP)粉体表面沉积贵金属铂(Pt), 制备低Pt担载量Pt(0.80 wt%)/GaP和高Pt担载量Pt(4.2 wt%)/GaP纳米粉体样品. 在可见光照射条件下, 分别以GaP和Pt/GaP纳米粉体作为光催化剂, 对结晶紫水溶液进行光催化降解. 实验结果表明, GaP和Pt/GaP两种纳米粉体皆具有可见光响应光催化性能; Pt担载量对Pt/GaP纳米粉体的光催化性能有着较大的影响, 低Pt担载量Pt(0.80 wt%)/GaP纳米粉体的结晶紫光催化脱色率高于GaP纳米粉体, 而高Pt担载量Pt(4.2 wt%)/GaP粉体的结晶紫光催化脱色率则低于GaP纳米粉体.     

杂CeO2的TiO2光催化降解甲醛的研究

采用液相合成法制备CeO2改性TiO2光催化粉体,利用X射线衍射仪、紫外-可见分光光度计、X射线光电子能谱等对粉体的晶相组成、光谱吸收性能等进行了表征,结果表明:改性后的TiO2经800℃热处理后仍呈锐钛矿结构;CeO2/TiO2吸收光谱的阈值波长红移至450nm;改性后TiO2表面的化学吸附氧含量增加.光催化降解甲醛的结果表明,粉体在普通日光灯下对甲醛气体的降解率明显优于P25.     

La3+离子掺杂对纳米ZnO光催化性能的影响

采用共沉淀法,选择尿素为沉淀剂,制备了一系列不同La3 掺杂浓度的纳米ZnO粉体.讨论了不同掺杂浓度的样品催化降解甲基橙的光催化活性,并通过X射线衍射(XRD)和透射电镜(TEM)等分析测试手段研究了粉体样品的相组成、晶胞参数和晶粒大小对光催化性能的影响.结果表明:La3 掺杂能够显著提高ZnO粒子的光催化活性.最佳掺杂浓度为100:0.2;最后提出了La3 改善纳米ZnO粉体光催化性能的作用机制.     

纳米TiO2光催化剂的结构调控及其光催化活性研究

以酞酸丁酯和冰醋酸分别为前驱物和酸催化剂,采用溶胶 凝胶法制备了纳米 TiO2 粉体, 并且通过改变水体溶液中酞酸丁酯,醋酸和水的摩尔比来调控纳米TiO2 粉体的大小以及光催化活性;探讨在溶胶 凝胶法制备过程中在水溶液中添加表面活性剂十二烷基苯磺酸钠 ( DBS ) 和共溶剂无水乙醇(CH3CH2OH)来调控TiO2 粉体以及光催化活性。用X射线衍射和透射电子显微镜等手段对不同条件制备的纳米粉体的微观结构进行了表征,并且以甲基橙染料的降解为模型反应,考察了不同制备条件下的催化剂的光催化活性,而且对纳米粉体结构和光催化性能之间的关系进行了讨论。     

TiO2/Pr2O3纳米粉体的制备、表征及光活性

利用酸催化的sol-gel法制备了纯TiO2和Pr3 (1.25%)掺杂TiO2纳米粉体,采用XRD、BET、XPS、DRS和SPS等技术对其进行了表征,以亚甲基蓝(MB)的光催化降解为探针反应,评价了其光活性,探讨了Pr3 掺杂对TiO2纳米粉体的光活性的影响机制.研究表明:与纯TiO2相比,TiO2/Pr2O3纳米粒子的光活性显著提高;掺杂Pr3 可以强烈抑制TiO2由锐钛矿向金红石的相变,阻碍晶粒生长,提高高温组织稳定性,改善粉体的表面织构特性,增加粉体的表面羟基和吸附氧含量;Pr3 掺杂能促进光生e-/h 的分离,提高光生e-/h 的氧化还原能力,改善样品表面的吸光性能.由于产生了量子尺寸效应,复合粉体的紫外吸收带边蓝移.     

纳米Bi_2O_3的制备及其可见光催化活性

采用共沉淀法制备纳米Bi_2O_3,并将其应用于光催化,研究不同热处理温度下制备的Bi_2O_3的光催化降解甲基橙的活性。通过扫描电子显微镜、X射线衍射、紫外-可见吸收光谱和荧光光谱表征Bi_2O_3的形貌、结构、光学及光催化活性。结果表明:Bi_2O_3的光催化活性与热处理温度有关,热处理温度为400℃时,合成的Bi_2O_3在可见光照射180 min时,对甲基橙的降解率达到86%。良好的可见光吸收和较低的光生载流子复合是获得优异光催化活性的主要原因。     

Bi_(12)TiO_(20)粉体的熔盐法制备及光催化性能研究

以TiO_2(P25)和α-Bi_2O_3为原料,NaCl-KCl(摩尔比为1∶1)为熔盐,采用熔盐法制备出不同前躯体比例(α-Bi_2O_3/TiO_2)和不同煅烧时间的Bi12TiO20纳米粉体。利用X射线衍射、紫外-可见漫反射和扫描电子显微镜等表征手段对样品进行表征,发现熔盐法制备的粉体具有颗粒均匀和形貌单一等优点。通过在可见光照射条件下降解罗丹明B(RhB)活性的研究,探讨了其光催化能力及降解机理。结果表明:前躯体摩尔比为4,煅烧时间2h制备的纳米粉体具有最好的光催化性能,这主要是因为其具有较规则的暴露晶面和存在的异质结结构,有利于光生电子-空穴对的分离。     

Eu3+和Sm3+共掺杂TiO2光催化剂的协同效应

采用溶胶-凝胶法制备了纯TiO2和Eu3+/Sm3+共掺杂TiO2复合粉体,采用XRD,DRS和SEM等技术进行表征,以亚甲基蓝(methylene blue,MB)的光催化降解为目标反应,评价了其光催化活性,探讨了Eu3+/Sm3+共掺杂对TiO2粉体光催化的影响机制.结果表明,Eu3+/Sm3+共掺杂可以显著提高TiO2粉体光催化活性,Eu3+/Sm3+共掺杂在TiO2粉体中产生协同作用,可以抑制TiO2由锐钛矿相向金红石相转变,使TiO2的粒径减小.Eu3+/Sm3+共掺杂增大了TiO2粉体的晶格畸变,使TiO2粉体吸收带边蓝移.当Eu3+/Sm3+的掺杂量分别为0.05%和0.1%,TiO2光催化活性最高,光催化降解率达到84.8%.     

Pt／TiO2纳米粒子的制备及其光催化性能研究

采用溶胶-凝胶法制备了掺杂Pt的TiO2粉末，利用紫外可见光谱对粉末的光吸收性能进行了表征，并分别在模拟日光和可见光下考察了其光催化氧化对．硝基苯酚的活性。结果表明，掺杂Pt以后TiO2粉末的光谱吸收范围被拓展至可见光，光催化活性也明显提高。在模拟日光照射下，以光催化活性较好的Pt／TiO2粉末为催化剂降解对．硝基苯酚，4h后对-硝基苯酚的转化率为93．7％，其反应是一级反应。     

微乳液法合成新型可见光催化剂BiVO4及光催化性能研究

以Bi(NO₃)₃、NH₄VO₃为原料,采用微乳液法合成了新型可见光活性的钒酸铋（BiVO₄）光催化剂,并利用XRD、SEM、XPS、BET等技术手段对其进行了表征. 以可见光(λ>400nm)为光源,以甲基橙的光催化降解为模型反应,考察了BiVO₄ 的可见光催化性能. 结果表明：采用微乳液法通过调节合成温度,可得到不同晶相的BiVO₄光催化剂. 四方相BiVO₄在低温下首先生成,随温度升高四方相开始向单斜相转变. 可见光催化实验结果表明,四方相和单斜相共混的BiVO₄的光催化效率最高,3h内使甲基橙的脱色率达到99.9%.     

Synthesis of visible-light responsive nitrogen/carbon doped titania photocatalyst by mechanochemical doping

Nitrogen and/or carbon doped titania photocatalysts TiO_2−x A _y (A = N, C) were prepared by a novel mechanochemical method. The samples were prepared by a high-energy ball milling of P25 titania with different nitrogen/carbon sources such as hexamethylenetetramine, admantane or ammonium carbonate, followed by calcination in air at 400 °C. The high mechanical energy accelerated the phase transformation of anatase to rutile, while the existence of the chemical reagents tended to block the transformation. The prepared powders possessed two absorption edges around 400 and 540 nm and showed excellent photocatalytic ability for nitrogen monoxide oxidation under visible light irradiation. Under the irradiation of visible light of wavelength >510 nm, 37% of nitrogen monoxide could be continuously removed by the carbon and nitrogen co-doped titania prepared by planetary ball milling of P25 titania–10% hexamethylenetetramine mixture followed by calcination in air at 400 °C. This mechanochemical technique might be widely useful for doping oxides with nonmetallic elements.     

炭包覆TiO2复合物对低浓度苯的光催化降解

通过将TiO2粉末和聚乙二醇混合,随后在氮气气氛下热处理合成了炭包覆TiO2.利用粉末X射线衍射、紫外-可见漫反射光谱、透射电子显微镜和氮吸附对炭包覆TiO2复合物样品进行了表征,并研究了其对浓度为～1.2×10-5苯的光催化活性.结果表明:炭包覆量受热处理温度和聚乙二醇用量的影响,随着温度的升高和聚乙二醇量的减少而减少;TiO2的结晶度随着温度的升高而提高,但是炭包覆对TiO2晶体的生长有抑制作用.炭包覆锐钛矿样品比纯TiO2表现出对苯更高的光催化活性,这是由于炭吸附作用导致锐钛矿颗粒周围的苯浓度增加以及包覆炭可导致电荷的有效分离;另一个原因是锐钛矿相结晶度的提高.因此,要获得对苯具有高光催化活性的炭包覆TiO2需要综合考虑碳含量和锐钛矿晶体结构.

Abstract：

Carbon-coated TiO2 was synthesized by mixing TiO2 powders and polyethylene glycol,followed by heat treatment in nitrogen atmosphere. All samples were characterized by powder X-ray diffraction,UV diffuse reflectance spectroscopy,high-resolution transmission electron microscopy,and nitrogen adsorption. The photocatalytic activity of carbon-coated TiO2 for benzene degradation was investigated with a benzene concentration of ～ 1.2 × 10-5. Results showed that the residual carbon content was influenced greatly by heat treatment temperature (HTT)and the amount of PEG,which decreased and increased with increasing the temperature and the amount of PEG,respectively. The crystallinity of TiO2 was improved when the HTT increased. However,the carbon residue had an inhibition effect on the crystal growth of TiO2. The carbon-coated anatase samples were shown to exhibit higher photocatalytic activities than the pristine TiO2 because of the adsorption enrichment of benzene by carbon around the anatase particles and of the effective charge separation due to the electronic conduction of carbon. Another important factor affecting photocatalytic activity was the crystallinity of the anatase phase. High photocatalytic activity for benzene requires a balance between the carbon content and the anatase crystalline structure.     

Mn-doped TiO2 nanopowders with remarkable visible light photocatalytic activity

TiO₂ nanocrystalline powders with various Mn-doping levels were synthesized by the sol-gel process using tetrabutyl titanate and manganese nitrate as precursors. The crystal structure, morphology, doping concentration, optical absorption property, and elemental state of the obtained samples were analyzed. TEM results showed that the synthesized TiO₂ powders were anatase nanoparticles about 7 nm in size. EDX and XPS analyses proved the incorporation of Mn ions into the TiO₂ lattice. A remarkable red shift of the absorption edge was achievable by increased Mn content, leading to gigantically narrowed energy gap to permit absorption well into the infrared spectral region. The dramatic optical absorbance of the doped TiO₂ nanopowders in the visible spectral region led to strong photocatalytic activity under visible light illumination, which was observed by measuring the degradation of methylene blue. In contrast, little degradation was observed for the pure TiO₂ powder. The optimum Mn/Ti ratio was observed to be 0.2 at.% for photocatalytic applications.     

Photocatalytic degradation of methyl orange dye by NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles under visible irradiation: effect of varying the synthesis temperature

Nanoparticles of nickel ferrites (NiFe₂O₄) were synthesized at different temperature of synthesis (25, 50 and 80 °C) through the chemical co-precipitation method. The synthesized powders were characterized using X-ray diffraction for crystallite size and lattice parameter calculation. It reveals the presence of cubic spinel structure of ferrites with crystallite size between 29 and 41 nm. Transmission electron microscopy and scanning electron microscopy showed uniform distribution of ferrite particles with some agglomeration. The Fourier-transform infrared spectroscopy showed absorption bonds, which were assigned to the vibration of tetrahedral and octahedral complexes. Raman spectroscopy is used to verify that we have synthesized ferrite spinels and determines their phonon modes. The thermal decomposition of the NiFe₂O₄ was investigated by TGA/DTA. The optical study UV–visible is used to calculate the band gap energy. Magnetic measurements of the samples were carried out by means of vibrating sample magnetometer and these studies reveal that the formed nickel ferrite exhibits ferromagnetic behavior. Photoluminescence showed three bands of luminescence located at 420, 440 and 535 nm. The photocatalytic properties of nickel ferrite (NiFe₂O₄) nanoparticles were evaluated by studying the photodecomposition of methyl orange as organic pollutant models and showed a good photocatalytic activity.     

Preparation and characterization of Co-doped TiO2 materials for solar light induced current and photocatalytic applications

Different amounts of Co-doped TiO₂ powders and thin films were prepared by following a conventional co-precipitation and sol–gel dip coating technique, respectively. The synthesized powders and thin films were subjected to thermal treatments from 400 to 800 °C and were thoroughly investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive analysis with X-rays, FT-infrared, FT-Raman, diffuse reflectance spectroscopy, ultraviolet–visible spectroscopy, BET surface area, zeta potential, flat band potential measurements, band-gap energy, etc. The photocatalytic ability of the powders was evaluated by methylene blue (MB) degradation studies. The thin films were characterized by photocurrent and ultraviolet–visible (UV–Vis) spectroscopy techniques. The characterization results suggest that the Co-doped TiO₂ powders synthesized in this study consist mainly anatase phase, and possess reasonably high specific surface area, low band gap energy and flat band potentials amenable to water oxidation in photoelectrochemical (PEC) cells. The photocatalytic degradation of MB over Co-doped TiO₂ powders followed the Langmuir–Hinshelwood first order reaction rate relationship. The 0.1 wt.% Co-doped TiO₂ composition provided the higher photocurrent, n-type semi-conducting behavior and higher photocatalytic activity among various Co-doped TiO₂ compositions and pure TiO₂ investigated.     

Synthesis of heterostructured In2O3/BiOCl powders and their visible-light-driven photocatalytic activity for the degradation of Rhodamine B

Heterostructured In₂O₃/BiOCl powders were synthesized by chemical coprecipitation method at room temperature followed by thermal treatment at 400 °C for 2 h. The TEM results confirmed the formation of sheet-like BiOCl nanostructures with the thickness of ca. 5–7 nm. In order to investigate the effect of In₂O₃ on the photocatalytic activity of heterostructured powders, the amount of In₂O₃ was varied from 0 wt% to 14 wt%. Adsorption and photocatalytic activity of the samples were evaluated for the degradation of Rhodamine B (RhB) in the dark and under visible light irradiation, respectively. The heterostructured In₂O₃/BiOCl powders showed high adsorption capacity and enhanced photocatalytic activity compared to P25 and pure BiOCl. Based on the results obtained in this study, the mechanism for the enhancement of photocatalytic activity of heterostructured In₂O₃/BiOCl powders is discussed. 10 wt% In₂O₃/BiOCl composite also exhibited good cycle performance for the degradation of RhB under visible light irradiation.     

Structural and optical studies of yttrium oxide nanoparticles synthesized by co-precipitation method

Yttrium oxide (yttria) nanoparticles were successfully synthesized by co-precipitation method. As-synthesized and annealed powders were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), UV-visible (UV-vis), photoluminescence (PL) spectra and Fourier transform infrared spectrometer (FTIR). The XRD results show that the as-prepared sample has mixed phase of Y(OH)₃ and yttria (Y₂O₃). However, cubic yttrium oxide phase alone is found for annealed samples. The strain values are calculated from Williamson-Hall (W-H) plot for annealed samples. SEM and TEM micrographs show that the samples are composed of aggregated nanoparticles with different shapes and sizes. From the UV-vis spectra, it is found that the position of the absorption peak is shifted towards the lower wavelength side when particle size decreases. In the PL spectra, the broad emission bands are observed between 340 and 380 nm and the presence of metal oxide is confirmed by FTIR spectra.     

AlCl3修饰对虎红-TiO2光催化剂可见光制氢活性的影响

用浸渍法制备了Rose bengal-Pt-TiO2和Rose bengal-AlCl3-Pt-TiO2光催化剂,通过可见光下光解水制氢考察了催化剂的催化活性.染料Rose bengal的敏化使TiO2在可见光照射下有较强的吸收和活性.催化剂Rose bengal-AlCl3-Pt-TiO2光催化活性高于Rose bengal-Pt-TiO2.其原因是经过AlCl3修饰的TiO2可以提高对染料Rose bengal的吸附量和吸附强度, 从而提高了TiO2的可见光催化活性.