Pt助剂对N掺杂TiO2可见光光催化性能的影响

考察了Pt促进的N掺杂TiO2(Pt/N-TiO2)催化剂对光催化降解有机污染物性能的影响及其作用本质.采用X射线衍射、透射电镜、X射线光电子能谱、紫外-可见漫反射光谱、光电化学和荧光光谱等手段对催化剂进行了表征,并考察了样品在可见光下光催化降解甲基橙(MO)的反应性能.结果表明,Pt的存在并未明显改变N-TiO2的晶...     

大孔-介孔氮掺杂二氧化钛的制备及其光催化性能测试

以嵌段共聚物为模板剂,甲酰胺为氮源,结合溶胶凝胶法制备了具有可见光活性的大孔-介孔氮掺杂二氧化钛(N-TiO2)材料.通过X射线衍射、低温N2吸附-脱附、扫描电镜、紫外-可见吸收光谱等手段,考察了嵌段共聚物对样品微结构和可见光活性的影响.结果表明,样品主要以锐钛矿相和板钛矿相混合形式存在;改变嵌段共聚物的浓度,可以制得晶粒粒径9～12 nm,孔径10～14 nm,禁带宽度2.98～2.76 eV的大孔-介孔N-TiO2,且随着模板剂加入量的增加,大孔孔径增大,孔壁增厚.对甲基橙溶液的室内自然光降解实验表明,大孔-介孔N-TiO2具有良好的光催化活性,随着嵌段共聚物加入量的增加,样品对甲基橙的降解时间缩短,降解率提高.     

N掺杂TiO_2纳米粒子表面光生电荷特性与光催化活性

以尿素为氮源,采用水热法制备了不同N掺杂量的TiO2(N-TiO2)光催化剂.利用X射线衍射(XRD),紫外-可见漫反射光谱(UV-Vis DRS),X射线光电子能谱(XPS)及荧光(PL)光谱等技术对其进行了系统的表征.以罗丹明B(RhB)和甲基橙(MO)溶液的脱色降解为模型反应,分别考察了N-TiO2光催化剂在紫外和可见光区的光催化活性.利用表面光伏(SPV)和瞬态光伏(TPV)技术研究了N-TiO2纳米粒子表面光生电荷的产生和传输机制,并探讨了光生电荷与光催化活性之间的关系.结果显示,随着N含量的增大,TiO2表面光伏响应阈值红移,可见光部分光电压响应强度逐渐增强,瞬态光伏响应达到最大值的时间亦有着不同程度的延迟.这表明适量的N掺杂能够提高TiO2纳米粒子中光生载流子的分离效率,相应地延长载流子的传输时间,增加光生电荷的寿命,从而促进其光催化活性;而过量的N掺杂则增加了TiO2纳米粒子中光生载流子的复合中心,抑制其光催化活性.     

WO_3/Bi_(12)SiO_(20)光催化降解气相苯

用气液反应法和化学溶液分解技术(CSD)分别制备了WO3和Bi12SiO20粉末,并将二者耦合,合成出WO3/Bi12SiO20复合光催化剂.以气相苯的降解为探针反应,考查了催化剂的光催化活性.结果表明:耦合后的WO3/Bi12SiO20催化剂的催化活性显著提高,其中30%(w)WO3/Bi12SiO20在紫外光下对苯的降解率明显优于P-25,而且催化剂具有一定的可见光响应能力.采用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、N2吸附-脱附(BET)和紫外-可见漫反射(UV-VisDRS)等手段对催化剂进行了表征.结果表明:WO3与Bi12SiO20之间存在良好的能带协同作用.WO3与Bi12SiO20耦合后,催化剂的光响应范围拓宽,光生电子和空穴能有效地分离,光生电子和空穴产生速率增大,所以催化剂活性提高.     

以尿素为氮源制备氮改性二氧化钛及其改性机理

以钛酸丁酯为前驱体,以尿素为氮源,采用改进溶胶-凝胶法制备了不同N含量的改性TiO2光催化剂(N-TiO2).以重铬酸钾为目标污染物,以甲酸为空穴捕获剂,评价了可见光下该催化剂的催化还原活性.结果表明,N-TiO2催化剂活性明显高于未改性催化剂,当催化剂中N/Ti摩尔比为10%、焙烧温度为400℃时,其光催化还原活性最...     

可见光响应光催化剂Ag/AgCl@NH2-UiO-66的制备及其光催化性能

采用气相扩散-沉积-光还原法制备了可见光响应复合光催化剂Ag/AgCl@NH₂-UiO-66.通过X射线衍射(XRD)、电子扫描显微镜(SEM)、X射线能谱(EDS)、紫外可见漫反射光谱及X射线光电子能谱(XPS)等对催化剂的结构进行了表征.结果表明Ag/AgCl@NH₂-UiO-66具有优良的光催化活性,可见光条件下(λ≥420 nm)对20 mg·L^-1罗丹明的降解效率14 min即可达到98%.     

可见光响应光催化剂Ag/AgCl@NH2-UiO-66的制备及其光催化性能

采用气相扩散-沉积-光还原法制备了可见光响应复合光催化剂Ag/AgCl@NH_2-UiO-66。通过X射线衍射(XRD)、电子扫描显微镜(SEM)、X射线能谱(EDS)、紫外可见漫反射光谱及X射线光电子能谱(XPS)等对催化剂的结构进行了表征。结果表明Ag/AgCl@NH_2-UiO-66具有优良的光催化活性,可见光条件下(λ≥420nm)对20mg·L~(-1)罗丹明的降解效率14min即可达到98%。     

掺杂不同pH值Bi_2WO_6对ZrO_2-TiO_2光催化降解苯的影响

将不同pH值下制备的Bi2WO6掺杂到共沉淀法制备的ZrO2-TiO2中合成一系列Bi2WO6-ZrO2-TiO2复合催化剂用于光催化降解苯。采用了X射线衍射(XRD),N2吸脱附,紫外-可见(UV-Vis)漫反射光谱,傅里叶红外变换光谱(FT-IR)和X光电子能谱(XPS)等手段对催化剂进行了表征。结果表明随着pH值的增大,催化剂晶粒尺寸减小,比表面积增大。Bi2WO6的掺杂降低了催化剂的禁带宽度,使催化剂感光范围拓展到可见光区。通过对气相苯的降解实验发现,掺杂pH=7的Bi2WO6的复合氧化物催化剂的紫外和可见光催化活性最高。     

NiFe2O4对刚果红的光催化降解性能研究

采用水热法合成了尖晶石型NiFe₂O₄,并利用X射线粉末衍射仪对其物相进行了表征,利用紫外-可见分光光度计对其光催化降解刚果红的性能进行了研究。以刚果红为光催化降解底物,探究了刚果红初始浓度、催化剂用量、溶液pH、不同光源等因素对NiFe₂O₄光催化降解刚果红活性的影响。结果表明,当刚果红溶液浓度为20 mg/L、催化剂NiFe₂O₄的用量为0.065 g、pH 2~10、在太阳光下照射480 min时,刚果红的降解率高达99%以上,催化剂性能稳定,适合处理刚果红类有机污染物。     

N-TiO2协同单过硫酸氢钾光催化降解氧氟沙星的研究

分别以尿素、钛酸四丁酯为氮源、钛源,利用溶剂热法制备氮掺杂二氧化钛光催化剂(N-TiO2),用XRD、SEM、IR、UV-vis DRS等对改性前后的催化剂进行表征.以LED灯为光源,氧氟沙星(OFX)为模型污染物,考察了N-TiO2协同单过硫酸氢钾(PMS)光催化降解OFX的性能.研究表明,当氮、钛摩尔比为0.6,O...     

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.     

Preparation and characterization of low-amount Yb3+-doped TiO2 photocatalyst

The nanoparticles of Yb³⁺-doped (0.125 wt.%) and pure TiO₂ were prepared by an acid-catalyzed sol-gel method and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy, and surface photovoltage spectroscopy; the specific surface of the samples was measured using the Brunauer-Emmett-Teller (BET) method. The photocatalytic degradation of methylene blue in aqueous solution was used as a probe reaction to estimate the photocatalytic activity of the prepared nanoparticles. The photocatalytic activity of Yb³⁺/TiO₂ composite nanoparticles is much higher than that of pure TiO₂. A low amount of Yb³⁺ in TiO₂ can inhibit the anatase-rutile phase transformation of TiO₂, prevent grain growth increasing the specific surface area, and favor the high-temperature stabilization of the pores. According to the surface voltage spectroscopy data, Tb³⁺-doping prevents recombination of photoinduced electrons and holes and improves the light absorption capacity of the particle surface. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1680–1685, October, 2006.     

Influence of N sources on the photocatalytic activity of N-doped TiO2

Influence of nitrogen precursors urea, semicarbazide and N,N’-dimethyl urea on the photocatalytic activity of the N-doped TiO₂ were studied by a simple decomposition method. The nano N-TiO₂ catalysts were synthesized via two different modified approaches by calcination at 500 °C. The synthesized samples were characterized by IR, UV-DRS, Raman, TG-DTA, XRD, EDX, XPS, SEM, TEM and BET analysis. Of the synthesized six samples of N-TiO₂ five samples showed better photocatalytic activity towards direct sunlight photo-degradation of methylene blue (MB) and rhodamine B (RhB) than Degussa P25. The catalysts obtained using semicarbazide samples F3 and F4 having large surface area of 76 and 85.8 m²/g displayed maximum photocatalytic activity. The sample F4 was 1.5 times more active than Degussa P25 for the decolourisation of MB and 1.9 times more active for the decolourisation of RhB. The presence of nitrogen, large surface area and coupling of rutile-anatase phases were found to be the main responsible factors for the enhanced photocatalytic activity. The exclusive formation of the anatase phase in the case of urea precursor is attributed to the slow evaporation of urea due to the formation of melamine derived products. The calcination temperature is the deciding factor responsible for the photocatalytic activity of the N-TiO₂ samples prepared from precursors which can potentially form the melamine and its oligomerized products on the surface of TiO₂.     

Characterization of mesoporous nanocrystalline TiO2 photocatalysts synthesized via a sol-solvothermal process at a low temperature

Nanocrystalline TiO₂ samples with mesoporous structure were prepared via a solvothermal treatment of surfactant-stabilized TiO₂ sols. The samples were obtained from media of different acidities including nitric acid, deionized water, and ammonia (denoted as HT-1, HT-2 and HT-3, respectively). These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂-sorption (BET surface area), micro-Raman spectroscopy, infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples were tested by the self-photosensitized degradation of an azo dye, Mordant Yellow 10 (MY), in aqueous solution under visible light irradiation. The results reveal that all three samples have high surface area and are pure anatase phase. The sample prepared in nitric acid medium possesses the most ideal mesoporous structure and also exhibits a blue shift in the Raman spectrum. All three samples show much higher photocatalytic activity than the commercial P-25. The activity order of the three samples is HT-1>HT-2>HT-3.     

Effect of nitrogen-doping temperature on the structure and photocatalytic activity of the B,N-doped TiO2

B,N-TiO₂ photocatalysts were synthesized by boron doping firstly and subsequently nitrogen doping in NH₃ at variable temperatures. The effects of the nitrogen doping temperature on the structure and photocatalytic activity of the B,N-codoped TiO₂ were investigated. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectrum (DRS), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated with photocatalytic degradation of methyl orange dye (MO) under visible light and UV-visible light irradiation. The results suggested that the boron and nitrogen can be incorporated into the TiO₂ lattice either interstitially or substitutionally or both, while the Ti-O-B-N structure plays a vital role in photocatalytic activity in visible light region. The optimal nitrogen doping temperature is 550 °C. Higher temperature may form many oxygen vacancies and Ti³⁺ species, resulting in the decrease of photocatalytic activity in visible light.     

Influence of crystallite structure of nanometer TiO2 catalysts on photocatalyst reaction

25 samples of nanometer TiO₂ were prepared through modifying the preparation conditions including the concentrations of Ti(SO₄)₂ and NH₄HCO₃, the pH value at the end of precipitation operation, and sintering temperature and time by methods of orthogonal design. The relationships between their catalytic activities of photocatalytic degradation of sodium dodecyl benzene sulfonate (SDBS) and the normal crystallite size, lattice-strain and X-ray diffraction intensity of 10 crystal faces were analyzed. It was discovered that the photocatalytic degradation reaction of SDBS follows first-order kinetics. Crystal faces of catalysts’ (101) have greater influence than other crystal faces on the reaction. The photocatalytic reaction needs more perfect (101) crystal faces with less lattice-strain. Smaller normal crystallite size and greater specific surface area of (101) crystal face are better for increasing reaction rate. The photocatalytic reaction is mainly proceeded on the (101) crystal face, comparatively, amorphous TiO₂ has lower catalytic activity.     

Vapor-thermal preparation of highly crystallized TiO2 powder and its photocatalytic activity

Nanocrystalline anatase TiO₂ powder photocatalysts were synthesized by a vapor-thermal method using tetrabutyl titanate as precursor at a temperature range from 120 to 200 °C. The as-synthesized products were characterized by X-ray diffraction, N₂ adsorption-desorption measurement, transmission electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectra, Raman spectra, and their photocatalytic activity was evaluated by photocatalytic oxidation decomposition of acetone in air. The results showed that reaction temperature greatly affected the microstructures and photocatalytic activity of the samples. With increasing reaction temperature and time, the average crystalline size of TiO₂ particles increased and their crystallization enhanced, while the specific surface area of the products decreased. The TiO₂ powders obtained at a temperature range from 150 to 200 °C for 10 h showed good photocatalytic activity and were greatly higher than that of Degussa P-25.     

Preparation of a highly active nanocrystalline TiO2 photocatalyst from titanium oxo cluster precursor

Nanocrystalline TiO₂ (sample S1) was prepared from a titanium oxo cluster (Ti₇O₄(OEt)₂₀) precursor via a sol-gel route. This photocatalyst showed a higher photocatalytic activity than the TiO₂ (sample S2) obtained from titanium tetraisopropoxide. The samples were characterized by thermal analysis (TGA/DSC), X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy, N₂ adsorption (BET surface area), infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy. The characterization results show that both samples are anatase nanocrystals with particle sizes of about 12 nm, but the more photocatalytically active sample S1 has more surface hydroxyl groups and larger surface area and pore volume than sample S2.     

不同形貌Bi4Ti3O12粒子的可控合成及光催化性能

研究了用一步水热法制备的不同形貌的钛酸铋(Bi₄Ti₃O₁₂, BIT)粒子的光学和可见光催化性能, 并对其晶体结构和微观结构用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段进行了表征. XRD结果表明, 所制备的BIT 样品为层状钙钛矿结构. FESEM结果表明, 通过控制水热过程的反应参数可以得到不同形貌的纳米粒子. 紫外-可见漫反射光谱(UV-Vis DRS)表明BIT 样品的带隙能约为2.88-2.93 eV. 利用可见光(λ>420 nm)照射下的甲基橙(MO)降解实验评价了BIT 样品的光催化性能. 结果表明, BIT 的光催化活性比掺氮TiO₂ (N-TiO₂)高得多. 研究了形貌对BIT 光催化性能的影响. 所制备的BIT纳米带光催化效率最高, 经可见光照射360 min, 甲基橙溶液的降解率可达到95.0%.