CTAB-assisted synthesis of mesoporous F-N-codoped TiO2 powders with high visible-light-driven catalytic activity and adsorption capacity

This article describes the preparation of mesoporous rod-like F-N-codoped TiO₂ powder photocatalysts with anatase phase via a sol-gel route at the temperature of 373 K, using cetyltrimethyl ammonium bromide (CTAB) as surfactant. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectra (UV-vis DRS). The results showed that the photocatalysts possessed a homogeneous pore diameter and a high surface area of 106.3-160.7 m³ g⁻¹. The increasing CTAB reactive concentration extended the visible-light absorption up to 600 nm. The F-N-codoped TiO₂ powders exhibited significant higher adsorption capacity for methyl orange (MO) than that of Degussa P25 and showed more than 6 times higher visible-light-induced catalytic degradation for MO than that of P25.     

TiO_2表面NiO光催化活性中心的构建及其光催化析氢性能研究

本文采用离子快速注入法,在低温条件下利用微量NiO物种对TiO_2光催化剂表面微结构进行了修饰和改性,构建了NiO光催化反应活性中心。研究结果表明,Ni物种是以TiO_2-NiO-H形式存在于TiO_2表面;相对于未修饰的TiO_2光催化剂,NiO的修饰很大程度上提高了其光催化析氢性能,在最佳条件下,放氢速率由1.1μmol·h~(-1)提高到241.4μmol·h~(-1)。另外,Ni物种含量,热处理温度,乙醇电子给体浓度,催化剂悬浮浓度对光催化析氢性能也有明显的影响。光电化学实验结果表明,NiO的表面修饰能够产生有效的光催化反应活性中心,增强了光生电子-空穴电子对的分离效果。所制备的光催化剂采用X射线粉末衍射(XRD),光电子能谱(XPS)等技术进行表征。     

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.     

Synthesis and visible light photocatalysis of Fe-doped TiO2 mesoporous layers deposited on hollow glass microbeads

Nano-composite of Fe-doped anatase TiO₂ nanocrystals loaded on the hollow glass microbeads was prepared by co-thermal hydrolysis deposition and calcining treatment. The adherence of TiO₂ mesoporous layers to the surfaces of hollow glass microbeads prevented the aggregation of TiO₂ nanoparticles and benefited to their catalytic activity. The doping of Fe ions makes the absorption edge of the TiO₂ based nano-composite red-shifted into the visible region. An effective photodegradation of the methyl orange aqueous solution was achieved under visible light (λ>420 nm) irradiation, revealing the potential applicability of such nano-composite in some industry fields, such as air and water purifications.     

TiO2纳米管阵列覆盖Si薄膜光催化还原CO2性能的研究

本工作采用CVD法在阳极氧化TiO2纳米管阵列膜表面沉积一层非晶Si膜,通过退火后得到晶化了的Si膜/TiO2纳米管阵列的复合结构,并初步就其光催化还原CO2制备碳氢化合物的活性进行研究。拉曼光谱(Raman)、X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、高分辨透射电子显微镜(TEM)等微结构表征结果表明所制备的TiO2纳米管阵列的厚度为270 nm左右,管直径约为70 nm,管壁厚度约为16 nm。覆盖的Si膜已晶化,其厚度约为300 nm。通过高效液相色谱(HPLC)及总有机碳(TOC)来检测光催化还原液相产物中的甲酸及总有机碳含量,发现负载Si膜后的TiO2纳米管阵列光催化性能有所提高,在装有400cut滤光片氙灯照射2 h下TOC含量从21.2 mg.L-1增长到29.5 mg.L-1,表明Si与TiO2的复合可有效的提高光催化还原CO2的活性,这可能与该异质结结构可增加对光的吸收并且可降低光生空穴-电子对复合有关。光催化循环实验表明所制得的催化剂在循环5次后仍可保持91.6%的催化活性。     

Preparation and characterization of mesoporous TiO2-CeO2 nanopowders respond to visible wavelength

Mesoporous TiO₂-CeO₂ nanopowders responding to visible wavelength were synthesized by using a surfactant assisted sol-gel technique. They were obtained using metal alkoxide precursors modified with acetylacetone (ACA) and laurylamine hydrochloride (LAHC) as surfactant. The samples were characterized by XRD, nitrogen adsorption isotherm, SEM, TEM, and selected area electron diffraction (SAED), respectively. The 95 mol% TiO₂-5 mol% CeO₂ system yielded single anatase phase, however, further addition of the CeO₂ formed cubic CeO₂ structure while anatase TiO₂ decreased. Additions of 5 and 10 mol% CeO₂ increased the surface area, but those of 25, 50, and 75 mol% CeO₂ did not affect it very much. By using this mixed metal oxides system, TiO₂ can be modified to respond to the visible wavelength. The mixed metal oxides had catalytic activity (evaluating the formation rate of I₃⁻) about 2-3 times higher than pure CeO₂, while nanosize anatase type TiO₂ materials had no catalytic activity under visible light. The catalytic activity was almost proportional to the specific surface area. The formation rate of I₃⁻ was much improved by changing the calcination temperature and calcination period. Highest catalytic activity in this study was obtained for the 50 mol% TiO₂-50 mol% CeO₂ nanopowders calcined at 250 °C for 24 h.     

The release of TiO2 and SiO2 nanoparticles from nanocomposites

There is a growing interest in the development of nanocomposites consisting of organic polymers and TiO₂ or amorphous SiO₂ nanoparticles. These nanoparticles may be released from nanocomposites. There is evidence that amorphous SiO₂ and TiO₂ nanoparticles can be hazardous. Thus, in the design of nanocomposites with such nanoparticles, hazard reduction extending to the full nanocomposite life cycle would seem a matter to consider. Options for hazard reduction include: changes of nanoparticle surface, structure or composition, better fixation of nanoparticles in nanocomposites, including persistent suppression of oxidative damage to polymers by nanoparticles, and design changes leading to the release of relatively large particles.     

金红石相TiO2纳米棒的氢化处理及其光催化活性

以钛酸四丁酯为钛源,通过盐酸调制的水热法制备出了具有棒状结构的金红石相纳米TiO₂,并进一步进行高温氢化处理. 采用X射线衍射（XRD）,透射电镜（TEM）,紫外-可见-近红外漫反射（UV-Vis-NIR DRS）,电子顺磁共振（EPR）和表面光伏（SPS）等测试手段对样品进行表征,以气相乙醛和液相苯酚为目标污染物考察催化剂的光催化活性. 结果表明：随着高温氢化处理时间的延长,TiO₂样品的可见光吸收逐渐增强,其颜色逐渐由白色转变成灰色,这主要与引入的Ti³⁺/氧空位缺陷有关. 表面光电压谱和羟基自由基测试表明,适当时间的氢化处理有利于光生电荷的分离. 在光催化氧化降解气相乙醛和液相苯酚过程中,经适当时间氢化处理的样品表现出高的可见光催化活性. 并且可见光催化活性的规律与紫外光下的是一致的. 这是因为氢化处理后在导带底下方引入了缺陷能级,拓展了可见光响应. 过度的氢化处理会在TiO₂导带下方引入较低的缺陷能级,使光生电荷的复合加剧,导致光催化活性降低.     

TiO2纳米纤维无纺布的制备及光催化性能研究

以聚乙烯吡咯烷酮(PVP)作为配位剂与钛酸正丁酯(Ti(C₄H₉O)₄)反应制得前驱体，再以乙醇为溶剂，CH3COOH作为催化剂，采用静电纺丝法制得PVP/TiO₂复合纳米纤维，经550 ℃、700 ℃和900 ℃焙烧后分别得到以锐钛矿型的TiO₂为主、以金红石型TiO₂为主和完全金红石晶型的TiO₂纳米纤维。对所制得的纳米纤维的结晶度、纯度和形貌，分别采用差热-热重分析(TG-DTA)、红外光谱(IR)、X射线粉末衍射(XRD)、扫描电镜(SEM)等进行了表征。光降解苯酚水溶液的实验结果表明，550 ℃下煅烧得到的以锐钛矿占主体的TiO₂纳米纤维，2 h使浓度为50 mg·L^-1苯酚水溶液的降解率超过85%，这充分说明这种TiO₂电纺纳米纤维具有良好的光催化性能。     

Synthesis and photocatalytic activity of co-doped mesoporous TiO2 on Brij98/CTAB composite surfactant template

Using composite surfactant templates, polyoxyethylene (20) oleyl ether (Brij98) and cetyl trimethyl ammonium bromide (CTAB), as structure-directing agents, N and La co-doped mesoporous TiO₂ complex photocatalysts were synthesized successfully. The micromorphology of co-doped mesoporous TiO₂ samples was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FT-IR), energy-dispersive X-ray spectrometer (EDS) and N₂ adsorption-desorption measurements. The results indicated that the complex photocatalyst prepared with a molar ratio of Brij98:CTAB=1:1 showed a uniform pore size of ca. 7 nm and a high specific surface area (S_BET) of 279.0 m² g⁻¹, and exhibited the highest photocatalytic activity for degradation of papermaking wastewater under ultra-violet light irradiation. The chemical oxygen demand (CODc_r) percent degradation was about 73% in 12 h and chroma percent degradation was 100% in 8 h.     

Synthesis and Characterization of TiO2/YFeO3 and Its Photocatalytic Oxidation of Gaseous Benzene

YFeO₃ was prepared by coprecipitation method and citric acid method, and TiO₂/YFeO₃ heterosystem photocatalysts were synthesized by loading TiO₂ sol on the surface of YFeO₃via sol-gel method. Their photocatalytic activities were evaluated by the decomposition of gaseous benzene under UV light illumination. The prepared photocatalysts were characterized by nitrogen adsorption-desorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis diffuse reflectance spectroscopy. Results revealed that the heterosystem photocatalysts prepared by coprecipitation method showed higher activity, and the maximum conversion of benzene could reach 44.7% within 180 min. The YFeO₃ samples prepared from coprecipitation method and citric acid method were absolutely in orthorhombic phase. The deposited titania was dispersed on the surface of carrier and a certain interaction existed between TiO₂ and YFeO₃. The two heterosystems photocatalysts had narrow band-gap energies.     

TiO_2纳米带光催化二氧化碳甲烷化

研究了在常温常压下TiO2纳米带光催化CO2催化加氢气反应。在紫外光照射下,二氧化碳的加氢还原产物为甲烷。利用高分辨TEM,XRD,UV-Vis DRS,低温氮吸附-脱附,TG等考察了催化剂与甲烷产率的构效关系。结果表明,在600℃焙烧时得到的双晶材料具有最佳的光催化活性。优异的光催化活性主要得益于TiO2双晶脱水纳米带(DNR Bicrystalline dehydratednanoribbon)。上面形成的纳米晶界能够提高催化剂在紫外区的光吸收能力,TiO2(B)和锐钛矿独特的双晶间隔结构也提高了界面电荷分离的效率。担载贵金属Pt显著地提高了反应速率。     

双介孔结构的纳米TiO2/I2复合材料的制备及其可见光催化性能

以钛酸丁酯为前驱体, 碘溶胶为碘源, 在室温下采用水解沉淀法制备了单质碘和纳米TiO₂复合的双介孔结构光催化剂(M-I₂-TiO₂). 采用X射线衍射(XRD)、透射电子显微镜(TEM)、比表面分析(BET)、紫外-可见(UV-Vis)漫反射光谱和傅里叶变换-红外光谱(FT-IR)对M-I₂-TiO₂进行了表征. 以次甲基蓝(MB)溶液为模拟废水, 对M-I₂-TiO₂的光催化性能进行了评价, 研究了不同热处理温度对光催化活性的影响. 结果表明, M-I₂-TiO₂在可见光区有显著的吸收, 300 ℃热处理得到的样品比表面积高达227.6 m²/g, 600 ℃热处理所得样品的比表面积仍高达111.8 m²/g, 而400 ℃热处理所得样品具有最好的光催化降解性能. 双介孔结构纳米TiO₂/I₂复合材料的光催化降解性能显著高于相同方法制备的纯TiO₂和Degussa P-25商业产品. 催化剂经6次重复使用其光催化活性基本保持不变.     

载有C60的TiO2纳米粒子光催化活性

以水溶性C₆₀和TiO₂粒子为前驱体,采用水热法制备了载有C₆₀的锐钛矿型TiO₂纳米粒子。应用X射线衍射、透射电子显微镜、红外光谱、紫外-可见漫反射光谱、荧光光谱对产物进行了表征。以对-硝基苯酚为模型污染物研究了产物的光催化活性,结果表明适量负载C₆₀可以提高TiO₂纳米粒子的光催化活性,C₆₀起着传输电子、促进TiO₂光生载流子分离的作用,且经7次循环使用后对-硝基苯酚的降解效率仍能达到74%。讨论了载有C₆₀的TiO₂纳米粒子光催化降解对-硝基苯酚的机理。     

Ag/TiO2光催化还原硝酸氮

利用化学还原法制备不同Ag掺杂量TiO₂纳米催化剂,采用TEM、XRD、XRF和UV-Vis对催化剂进行表征。考察了催化剂在紫外光(254 nm)和可见光照射下还原初始浓度100 mgN·L^-1水相硝酸氮的活性和效果。重点考察了紫外光照射下Ag掺杂量、不同空穴捕获剂(甲酸、甲醇、乙酸、乙醇、草酸、草酸钠等)及甲酸浓度对硝酸氮还原的影响;对硝酸氮转化率和总氮去除率、形成亚硝酸氮、氨氮浓度及氮气选择性的影响。甲酸浓度为0.030 mol·L^-1、Ag掺杂量为1.0wt%时催化剂效果最佳。此时,硝酸氮、总氮的转化率分别为98.43%、78.13%;亚硝酸氮浓度为零,转化的硝酸氮中只有20.76%转化为氨氮,氮气选择性为79.24%。可见光下进行光催化还原反应时,硝酸氮转化率仅37.98%,但氮气的选择性较高。     

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。     

火焰辅助热解方法制备Ag_2O/TiO_2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Ag_2O/TiO_2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TiO_2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TiO_2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Ag_2O。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Ag_2O通过光生电子转化为Ag形成Ag/TiO_2,进一步提高光催化制氢活性。     

Photo-induced transformation of hexaconazole and dimethomorph over TiO2 suspension

The photo-induced transformation in aqueous solution of hexaconazole and dimethomorph over irradiated titanium dioxide was studied. The investigation involved monitoring pesticides decomposition, identifying intermediate compounds, assessing mineralization, and evaluating toxicity of pesticides derivatives. HPLC/UV and HPLC/MS were used to follow the disappearance of the initial pesticides and the formation of intermediate products, while the acute toxicity was evaluated by using the Vibrio fischeri luminescent bacteria assay.Hexaconazole photocatalytic transformation proceeds through the formation of highly persistent compounds. The formation of cyanuric acid, a non-toxic compound refractory to photocatalytic treatment, was recognized. Conversely, the toxicity assays prove that neither hexaconazole nor its intermediates exhibit acute toxicity.Dimethomorph under photocatalytic treatment is completely mineralized within 14 h of irradiation. However, its transformation proceeds through the formation of toxic intermediates. A correlation exists between the evolution of the intermediate compounds and the toxicity profile, as the highest toxicity is measured when the intermediates with lower EC50 (hydroquinone and 4-chlorophenol) are formed.     

TiO2/LaFeO3微纳米纤维的可控制备及光催化性能简

利用静电纺丝技术及水热合成法制备了TiO2/LaFeO3异质结构. 采用场发射扫描电子显微镜(FE-SEM),X射线衍射(XRD),傅里叶变换红外(FTIR)光谱和紫外-可见漫反射光谱(UV-Vis)等手段对TiO2/LaFeO3微纳米纤维的结构和表面形态进行表征. 通过亚甲基蓝(MB)光降解反应研究了其光催化性能. 结果表明,不完全碳化TiO2纤维表面的缺陷位点是LaFeO3纳米粒子的有利生长点. TiO2/LaFeO3异质结材料的带隙明显窄于TiO2,光催化活性得到提高;经140 min紫外光照射后,TiO2/LaFeO3异质结催化剂对MB的降解率为65.34%,分析和探讨了其光催化机理.     

CNTs/TiO2多孔复合膜的组装及光催化性能

提出了一种在掺氟的SnO2(FTO)导电玻璃上组装碳纳米管(CNTs)/Fe-Ni/TiO2多孔复合膜光催化剂的新方法.采用喷涂热解法(SPD)将掺杂镍和铁的含有嵌段聚合物P123的二氧化钛前驱体溶胶涂覆在FTO导电玻璃上,制备Fe-Ni/TiO2多孔膜,再采用化学气相沉积法(CVD)在Fe-Ni/TiO2膜上原位生长CNTs,得到CNTs/Fe-Ni/TiO2多孔复合膜光催化剂.CNTs/Fe-Ni/TiO2复合膜具有多级孔结构特征,在TiO2表面原位生长的CNTs不但具有较好的石墨化结构,且CNTs较均匀地分布在整个膜层的孔中.考察了CNTs/Fe-Ni/TiO2复合膜光催化剂的结构和性能,并通过降解甲基橙溶液评价了复合膜的光催化活性.结果表明,CNTs的复合及铁和镍的掺杂等改性显著提高了TiO2膜材料的光催化活性.