Visible photocatalytic activity of Ti-doped LaNi03 synthesized by solution combustion synthesis

采用溶液燃烧法制备了一系列不同Ti掺杂量的LaNiO3光催化剂，研究了Ti掺杂量对其相结构、形貌和光催化性能的影响。采用XRD、SEM、EDS及光致发光光谱（PL）等对其进行了表征和分析。结果表明：采用溶液燃烧法可获得单一钙钛矿相的LaNiO3，随着Ti掺杂量的增加，晶面间距逐渐增大；Ti掺杂量对颗粒的形貌大小影响较小，颗粒近似球形，粒径分布均匀，约为80nm。可见光催化实验结果表明，当Ti掺杂量为3．0％（质量分数）时，所得催化剂的催化效果最好，适量的Ti掺杂可显著降低光生载流子的复合几率。     

CNTs/TiO2复合物制备及光催化性能研究

在不使用表面活性剂的情况下, 采用溶胶-凝胶法成功制备CNTs/TiO₂复合物, 利用XRD、TEM、HRTEM和SAED对样品的结构和形貌进行了表征。选取亚甲基蓝溶液为目标降解物, 利用紫外-可见(UV-Vis)分光光度计考察了CNTs/TiO₂复合物的光催化活性, 系统研究了CNTs掺杂量对催化降解效率的影响。实验结果表明: 经450℃煅烧, 锐钛矿相TiO₂通过C-O-Ti键均匀地涂覆在CNTs表面, TiO₂颗粒尺寸约16 nm。CNTs/TiO₂复合物光催化活性明显高于纯TiO₂, 当CNTs掺杂量为1wt%时, CNTs/TiO₂复合物对亚甲基蓝的催化降解效率最高, 比纯TiO₂提高11.7%。     

纳米Fe-TiO2可见光下光催化降解罗丹明B

汞灯、氙灯以及紫外灯，广泛用于光催化处理水体污染和研究。为减少这种高能耗光源的使用，实验采用溶胶-凝胶法制备了一种可在低耗LED灯下响应的铁掺杂纳米二氧化钛光催化剂。分析了其物相组成，微观形貌结构以及紫外和红外的光学吸收性质。在LED白灯照射条件下，探讨了Fe掺杂量、溶液初始浓度、初始pH对模拟废水罗丹明B溶液光催化降解的影响，并分析了其降解机理。结果表明，Fe³⁺的掺入加快了TiO₂锐钛矿相向金红石相的转变。在扫描电镜下纳米颗粒分布较均匀，团聚不明显。Fe³⁺的掺杂减小了TiO₂的禁带宽度并使光学吸收边红移，禁带宽度从3.2 eV显著降低到2.7 eV;但当Fe³⁺掺量过大时，纳米Fe-TiO₂光学吸收边蓝移，在可见光区域的活性明显降低。综合分析得：在摩尔比n(Fe)∶n(Ti)=0.3%,pH=7,经LED白灯(100 W)照射72 h,对罗丹明B去除率达89%。为利用低能耗LED灯光催化降解有机污染物提供参考。     

溶液燃烧制备镧基钙钛矿及其催化碳烟燃烧性能

采用溶液燃烧法制备不同B位过渡金属元素(Mn、 Fe、 Co、 Ni)的La基钙钛矿(LaMO₃)催化剂，并考察少量Sr部分取代La对催化剂性能的影响；通过XRD、 SEM、 BET、 H₂-TPR、XPS方法对催化剂进行理化性质表征，采用程序升温氧化(TPO)技术评估催化剂催化碳烟燃烧的性能。结果表明：溶液燃烧法制备的La基催化剂具有典型的钙钛矿结构，少量Sr掺杂不改变催化剂的晶型；Sr掺杂LaMnO₃引起的电荷不平衡由增加的Mn⁴⁺补偿，Sr掺杂LaCoO₃使吸附氧量明显提高；La_0.9Sr_0.1MnO₃和La_0.9Sr_0.1NiO₃的氧化还原性能相比掺杂Sr之前的有所下降，La_0.9Sr_0.1FeO₃表面吸附氧物种量增多，催化剂的低温氧化还原性提升；气氛中NO_x     

溶液燃烧合成LaFe1-xMgxO3超细粉体及其光催化性能

采用溶液燃烧合成Mg²⁺掺杂LaFeO₃超细粉体, 并利用XRD、SEM、BET和UV-VIS分析Mg²⁺掺杂量对合成粉体的物相组成、微观形貌和光催化性能的影响。结果表明: Mg²⁺取代Fe³⁺形成LaFe_1-xMg_xO₃ (0≤x≤0.2)有限型固溶体。当掺杂量为0.1时(x=0.1), 合成粉体具有最大的比表面积(43.46 m²/g)和较小粒径(径向和长度方向分别为100 nm和150 nm), 因此具有最佳的光催化性能, 在高压汞灯180 min照射下, 对甲基橙溶液(10 mg/L)的降解率达75.2%, 与纯LaFeO₃的相比, 光降解率增加26.5%, 且光催化反应符合一级动力学方程。     

钛掺杂三氧化钨薄膜结构与电致变色性能研究

通过射频溅射法, 常温下制备了纯相WO₃和Ti掺杂WO₃薄膜, 采用XRD、SEM、Raman、电化学工作站、紫外-可见-近红外分光光度计等对薄膜的微观结构、循环稳定性、光学性能进行了表征和分析。研究发现: 钛掺杂对WO₃薄膜的表面形貌和光学常数影响不明显, 但使薄膜的晶化温度升高。电化学测试结果表明, Ti掺杂可以提高离子在薄膜中注入/抽出的可逆性, 提高薄膜的循环稳定性, 同时薄膜的响应速度和光学调制性能也得到提高, 掺杂后薄膜着色态和漂白态的响应时间分别由9.8、3.5 s减小为8.4、2.7 s, 因此Ti掺杂WO₃薄膜具有更好的电致变色性能。     

Ag3PO4/MIL-125(Ti)Z型异质结的构建及其光催化还原Cr(Ⅵ)的性能

将Ag₃PO₄纳米颗粒原位沉积在圆饼状MIL-125(Ti)的表面制备出Ag₃PO₄/MIL125(Ti) Z型异质结光催化剂,分别用XRD、SEM、EDS、UV-vis、FTIR、EIS和PL等手段表征其晶相结构、形貌特征、光吸收性能、价带结构和电荷分离效率,研究了在模拟太阳光照射下Ag₃PO₄沉积量不同的Ag₃PO₄/MIL125(Ti)光催化剂还原Cr(Ⅵ)的性能,以及在光催化过程中初始溶液的p H值和催化剂投加量等的影响。结果表明,Ag₃PO₄的沉积有效提高了MIL-125(Ti)光催化还原性能。Cr(Ⅵ)溶液初始浓度为10 mg/L、pH为2时,Ag₃PO₄/MIL-125(Ti)-2对Cr(Ⅵ)的还原率可以达到96.9%。带隙结构计算和自由基捕获实验的结果表明,Ag₃PO₄     

Pr掺杂Mg2SnO4纳米颗粒的制备及其光致发光性能

采用水热合成和低温煅烧两步法工艺制备了不同浓度(0~1.5mol%)镨掺杂锡酸镁, 通过X射线衍射(XRD)、扫描电子显微镜(SEM)及荧光光谱仪对合成的样品进行表征, 研究了Pr掺杂量对锡酸镁微观形貌的影响, 并讨论了其光致发光性能。结果表明, 所制备的Mg₂SnO₄: Pr³⁺为立方反尖晶石结构的立方纳米颗粒; 与未掺杂的Mg₂SnO₄相比, Pr掺杂浓度的增加使颗粒尺寸变大, 并使颗粒边角锐化。不同浓度Mg₂SnO₄: Pr³⁺的发射光谱表明Mg₂SnO₄: Pr³⁺样品中存在530、570 nm两处发射峰, 前者与Mg₂SnO₄基质中的氧空位有关, 后者由Pr元素³P₀-³H₅能级的跃迁造成。随着Pr掺杂浓度增加, 锡酸镁颗粒尺寸变大、发光中心增多, 使得Pr掺杂锡酸镁纳米颗粒在570 nm处的发光强度增强。     

改性纳米TiO2的制备及光催化降解重金属废水的研究

以钛酸丁酯为钛源,硝酸铈为改性剂,通过溶胶-凝胶法制备了不同稀土Ce掺杂量(0,0.3%,0.6%和0.9%(摩尔分数))的改性纳米TiO2粒子。采用XRD、SEM、UV-Vis、PL和光催化测试等,研究了不同稀土Ce掺杂量对纳米TiO2粒子物相结构、微观形貌、光谱性能和光催化性能的影响。结果表明,制备出的纳米TiO₂粒子均为锐钛矿相,且结晶度较高;掺入稀土Ce后,纳米TiO₂粒子的形貌逐步变为规则的球形,晶粒得到了细化,当稀土Ce的掺杂量为0.6%(摩尔分数)时,TiO₂粒子的晶粒尺寸最为规则,分布最为均匀;稀土Ce掺杂的纳米TiO₂粒子的吸收边带发生了红移,吸收边带增大,稀土Ce的掺杂有效抑制了电子-空穴对的复合;稀土Ce改性纳米TiO₂粒子对重金属废水中Cr(Ⅵ)的降解效率得到了明显提高,当稀土Ce的掺杂量为0.6%(摩尔分数)时,纳米TiO₂在180 min时的降解效率最高为92.7%,相比纯纳米TiO₂的降解效率,提高了16...     

溶胶-凝胶法制备Gd4Ga2O9: Dy3+白光发射荧光粉及其性能

通过溶胶-凝胶法制备了具有白光发射的Gd₄Ga₂O₉:x%Dy³⁺荧光粉,利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、紫外-可见漫反射光谱(UV-Vis DRS)和荧光光谱等对产物的物相结构、形貌、组分和光学性能进行研究,并分析了Dy³⁺掺杂量对样品的影响。XRD结果表明,所制备的样品为Dy³⁺掺杂的Gd₄Ga₂O₉单斜晶体和少量Ga₂O₃杂质相的混合物。紫外-可见漫反射光谱结果表明制备的Dy³⁺掺杂Gd₄Ga₂O₉晶体是一种光学带隙为5.29 eV的直接带隙半导体。荧光检测结果表明Dy³⁺掺杂Gd₄Ga₂O₉荧光粉可被属于Gd³⁺     

微波烧结制备MAX-cBN复合材料及其反应机理研究

采用Ti3SiC2与Ti3AlC2粉体和cBN粉体为原料,通过微波烧结制备Ti3SiC2与Ti3AlC2结合剂cBN复合材料,同时研究cBN的含量对该复合材料的物相组成与显微形貌的影响。结果表明,Ti3SiC2-cBN试样烧结后得到了SiC、TiSi2、TiC、TiO、TiO2、SiO2。cBN添加量为10%的复合材料中Ti3SiC2分解较为严重。试样烧结后基体组织比较细小,只有几微米。当原料中cBN含量为20%时,cBN表面会形成凹凸不平的组织。Ti3AlC2-cBN试样烧结后得到了Ti2AlC、TiC、Ti、Al、Al2O3,Ti3AlC2材料分解完全。cBN含量较高时,它可以与Ti3AlC2或其分解产物充分反应,形成相应的氮化物或碳氮化物。     

Synthesis and photocatalytic property of SnO2/TiO2 nanotubes composites

SnO2/TiO2 nanotubes composite photocatalysts with different SnO2 contents were successfully synthesized by means of a simple solvothermal process. The synthesized products were characterized physically by X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM). The composite photocatalysts can not only make the target pollutant, methylene blue (MB), adsorbed at a high concentration level around the surface of the composites but also decrease the recombination rate of electron-hole pairs so as to achieve good photocatalytic performance. The effect of SnO2 contents on the photocatalytic activities of the composites was also investigated. The results showed that the SnO2/TiO2 nanotubes composite photocatalyst with 5 wt.% SnO2 loading had the highest photocatalytic efficiency.     

Porous SrTiO3 spheres with enhanced photocatalytic performance

Porous SrTiO₃ spheres were successfully synthesized by a convenient hydrothermal method, employing SrCl₂ as Sr source and titanate nanotube as Ti precursor. In this reaction, when short titanate nanotube was used as Ti precursor, porous SrTiO₃ spheres were generated for the aggregation of the nanotube@SrTiO₃ heteronanostructure. Whereas long titanate nanowire was used as the Ti precursor, solid SrTiO₃ spheres were obtained due to the SrTiO₃ which grows up gradually on the titanate nanowire. The morphology and the pore size of the SrTiO₃ sphere structures can be easily controlled by simply adjusting the reaction time, reaction temperature and the Ti precursor. The porous SrTiO₃ spheres exhibited enhanced photocatalytic activity which could achieve 100% degradation of Rhodamine B with a UV irradiation for 20 min.     

Kinetic study of Cu(II) adsorption on nanosized BaTiO(3) and SrTiO(3) photocatalysts

In this study, nanoparticles with perovskite structure (nano-SrTiO(3) and nano-BaTiO(3)) were synthesized via a co-precipitation method, and their photocatalytic and adsorption characteristics were investigated. Both of them exhibited some photocatalytic activity and possessed a high adsorption capacity for copper ions. Further, the pseudo-first-order model was found to be more suitable to fit the experimental data. Moreover, it suggested that the Langmuir model was more adequate in simulating the adsorption isotherm. The maximum adsorption capacity was 370.4 mg/g and 200.0mg/g for nano-SrTiO(3) and nano-BaTiO(3), respectively. The negative apparent free energy confirmed that the Cu(2+) adsorption onto the nano-photocatalysts was a spontaneous process. The underlying mechanism of adsorption of Cu(II) onto nano-perovskites could be due to the ion exchange and surface complexation. From the results, SrTiO(3) and BaTiO(3) nanoparticles may be an effective material for Cu(2+) removal and, together with its photocatalytic activity, may be suitable for environmental remediation applications.     

Enhancing persistent luminescence and photocatalytic properties in Ti as a trap center in ZnGa<Subscript>2</Subscript>O<Subscript>4</Subscript>

ZnGa₂O₄ and ZnGa₂O₄:Ti phosphors were synthesized by the solid state method, and their persistent luminescence and photocatalytic properties were investigated in detail. The results of this study showed that Ti⁴⁺ doping improved the persistent luminescence properties. Thermoluminescence measurements demonstrated that the trap concentration considerably increased upon incorporation of Ti⁴⁺ ions into the ZnGa₂O₄ lattice. The traps generated by Ti doping were responsible for improvement in persistent luminescence. Furthermore, photocatalytic activity tests showed that the Ti-doped ZnGa₂O₄ phosphor exhibited much higher photocatalytic activity than the ZnGa₂O₄ host. UV–Vis diffuse reflectance spectra demonstrated that Ti-doped ZnGa₂O₄ shown a higher UV absorption efficiency. A comparison between the density of states of ZnGa₂O₄:Ti and ZnGa₂O₄ revealed that the bottom of the conduction band was modified by Ti doping. Hence, it could be concluded that Ti doping enhanced light harvest capability to generate more electron–hole pairs, and acted as a trap center by decreasing the recombination of photogenerated electrons and holes, resulting in the enhancement of both persistent luminescence and photocatalytic activity.     

Pt纳米颗粒负载SrTiO3/TiO2异质结结构制备及制氢性能

本文以固定n(Sr)/n(Ti)摩尔比0.4的SrTiO_3/TiO_2(金红石相)异质结纳米颗粒,通过"光催化还原沉积方法"制备不同质量分数的纳米铂颗粒(0、1%、2%、5%),探究其催化活性的变化,采用XRD、SEM、UV-vis、XPS方法对其进行表征,并做了相关光催化分解水产氢性能测试.结果表明:负载贵金属Pt纳米颗粒量越大,对应的Pt晶粒平均尺寸为40.8 nm,1%Pt纳米颗粒SrTiO_3/TiO_2异质结构的BET比表面积在23.195 m~2/g处最高,并且介孔材料的特征是平均Barrett-Joyner-Halenda(BJH)孔径为13.60 nm,总孔体积为0.079 cm~3/g;高BET表面积和大的总孔体积强烈地支持SrTiO_3/TiO_2具有介孔结构的事实;相应的催化剂催化活性越高,其中负载5%Pt纳米颗粒的SrTiO_3/TiO_2纳米颗粒光催化8 h产氢量为3.574 mmol,平均产氢效率为0.447 mmol/(gcat·h),但从性价比的角度来考虑,其催化效率远不及负载1%Pt纳米颗粒的SrTiO_3/TiO_2纳米颗粒催化效率的5倍,因此负载5%Pt的SrTiO_3/TiO_2纳米颗粒光催化效率最高.     

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.     

Decomposition behavior and dielectric properties of Ti-doped BiFeO3 ceramics derived from molten salt method

The effects of Ti-doping on the decomposition behavior, crystal structure, sintering behavior and dielectric properties have been investigated for the Ti-doped BiFeO₃ ceramics derived from molten salt method. XRD reveals the almost pure phase BiFeO₃ is synthesized in the Ti-doped BiFeO₃ powders. And the particle size of Ti-doped BiFeO₃ powers obviously decreases with the increase of Ti content. However, the sintering temperature elevates significantly after Ti-doping. The DC resistivity can enhance by up to four orders of magnitude (from 10⁴ to 10⁸?Ωm) with only 5 at% Ti doping. But the dielectric constant is suppressed from 10⁴ to 10², and dielectric loss obviously reduces with a small amount of Ti doping. The variation of dielectric properties has been discussed from the decomposition of BiFeO₃ phase. The Ti-doping can effectively suppress the decomposition reaction in Ti-doped BiFeO₃ ceramics.     

g-C3N4/g-C3N4 isotype heterojunction as an efficient platform for direct photodegradation of antibiotic

A visible-light-driven g-C₃N₄/g-C₃N₄ isotype heterojunction photocatalyst was synthesized by one-step thermal treatment using urea and thiourea as the precursor. The photocatalytic activity of as-prepared photocatalyst was evaluated through the degradation of rhodamine B (RhB) and tetracycline hydrochloride (TC) under the visible light irradiation. The hybrid showed enhanced photocatalytic activity in photodegradating the applied pollutants as compared with single g-C₃N₄. When the ratio of urea to thiourea was 2:1, the prepared isotype heterojunction exhibited the highest photocatalytic activity and the photodegradation rates for RhB and TC were 99.8% and 95.1% after being visible light irradiated for 1 h and 4 h respectively. The enhanced photocatalytic performance of the isotype heterojunction is ascribed to the enhanced charge separation efficiency. After being reused for 5 times, the hybrid still showed excellent recyclability and chemical stability. Furthermore, NaI, BQ and IPA were used as the sacrificial agents for studying the surface reactions in the photocatalytic process. The method used in this work provides a new pathway to achieve more efficient degradation of antibiotics and to stimulate further studies in this important field.     

β- and α-Bi2O3 nanoparticles synthesized via microwave-assisted method and their photocatalytic activity towards the degradation of rhodamine B

Amorphous β-Bi₂O₃ nanoparticles were synthesized directly via a liquid phase microwave reaction, and changed gradually into well crystallized sheet-like nanoparticles of β-Bi₂O₃ or α-Bi₂O₃ during the following calcining at lower (300 °C) or higher (350 °C) temperature. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and diffuse reflectance spectroscopy (DRS) were used to characterize the samples. The photocatalytic activity of the samples under simulated sunlight was also investigated by taking the degradation of rhodamine B (RB) as model reaction. β-Bi₂O₃ showed lower band gap energy and high absorbance in wider visible light region than α-Bi₂O₃ did, resulting in its higher photocatalytic activity. It was also found that higher crystallinity can improve the activity.