纳米氧化锌中空柱的制备及其光催化性能的研究

以醋酸锌和氨水为原料,超声法制备出氧化锌中空柱,采用扫描电镜(SEM)、X射线衍射(XRD)、Uv-vis漫反射对纳米ZnO的形貌、结构进行了表征,以有机染料亚甲基蓝溶液为光催化反应模型降解物,考察纳米ZnO的光催化性能。结果表明:制备出的纳米氧化锌呈中空的柱形,长约2～3μm,直径约300nm,壁厚约40nm,结晶良好。当加入纳米ZnO为0.4g/L,光降解时间为75min,对亚甲基蓝溶液的降解率可达到99.08%。     

复合纳米ZnO-SnO2粉体的电合成及光催化性能的研究

采用改进的电化学法制备了ZnO-SnO2纳米复合氧化物粉体,通过XRD、FT-IR、TEM等测试手段,对产物的物相组成、粒径大小、形貌等进行了表征;并考察了该纳米复合粉体的光催化活性.结果表明,得到的产物(氧化锌与氧化锡的复合物)颗粒分布均匀、平均粒径约为30～50 nm;该复合氧化物对甲基橙及亚甲基蓝溶液的光催化降解明显优于单纯的ZnO或SnO2;前驱体的焙烧温度以及ZnO和SnO2的复合摩尔比对ZnO-SnO2的光催化活性有较大的影响.     

MOF衍生的多孔ZnO/C、Ag/ZnO/C复合材料光催化性能研究

以金属有机骨架(MOF-5)为前驱体, 通过高温热处理和湿化学法获得ZnO/C和Ag/ZnO/C两种光催化复合材料。采用X 射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱(EDS)和紫外-可见分光漫反射(UV-Vis DRS)等方法对所得样品的晶体结构、形貌特征、组成及光谱特性进行了表征。结果显示, 高温热处理保留了MOF-5的原始结构。ZnO/C比表面积为390 m²/g, 载银后比表面积仍达232 m²/g, 负载的银颗粒尺寸约30 nm。光催化降解实验表明ZnO/C和Ag/ZnO/C复合材料对亚甲基蓝(MB)都具有很高的降解效率, 均优于商业TiO₂。Ag/ZnO/C的光催化性能更好, 且具有较好的重复利用和稳定性。因此, 适度的高温碳化和掺杂贵金属是获得优良光催化性能的根本原因。     

ZnO纳米棒的绿色合成及光催化性能研究

以Zn(Ac)2·2H2O和NaOH为反应物,以离子液体1-十二烷基-3-甲基咪唑四氟硼酸盐[C12mim][BF4]水溶液为反应介质,80℃下制得ZnO纳米棒。采用透射电子显微镜(TEM)、X射线衍射(XRD)和紫外可见吸收光谱(UVVis absorption spectra)对纳米ZnO的形貌和结构进行了表征,以有机染料亚甲基蓝溶液为光催化反应模型降解物,考察纳米ZnO的光催化性能。结果表明,制备出的纳米氧化锌呈棒状,宽约10nm,长约160nm,为六方纤锌矿结构。紫外灯照射120min后,对亚甲基蓝溶液的降解率可达到86.3%。     

纳米TiO2微球的制备及光催化性能研究

以钛酸四丁酯为前驱体,在油酸和正己烷的混合溶剂中,采用溶剂热技术成功地合成了纳米TiO2微球.以X射线衍射(XRD)、透射电镜(TEM)等方法对产物进行了表征,并对其光催化降解甲基橙溶液的性能进行了研究.实验结果表明:纳米TiO2微球的平均尺寸约为60nm,其中含有粒径平均约4.5nm的超细粒子.此种结构趋向于高的比表面积,与P-25型光催化剂相比,两者对甲基橙溶液的脱色具有相近的光催化活性.     

氧化锌/氧化镁纳米复合材料的制备及其光催化性能研究

采用微波辅助共沉淀法制备了纳米氧化锌/氧化镁(ZnO/MgO)光催化剂,并对催化剂样品进行了X射线衍射、透射电镜、红外光谱以及紫外-可见吸收光谱等表征。以亚甲基蓝(MB)为目标降解物对不同锌镁比的ZnO/MgO催化剂样品及相同方法下合成的ZnO及MgO进行光催化降解实验。结果表明:合成的纳米ZnO/MgO光催化剂由立方相的ZnO和非晶相的MgO组成,其尺寸均匀,在40nm左右,并在紫外区域吸收性能良好。光催化降解MB实验表明,锌镁比为2∶1时ZnO/MgO催化剂的光催化性能最佳。     

以四氯化钛和钛酸四丁酯为前驱体的TiO2/C杂化气凝胶光催化性能比较

采用一步溶胶-凝胶法,以四氯化钛、钛酸四丁酯为钛基前驱体,间苯二酚、糠醛为有机相前驱物,制备出TiO2/有机杂化湿凝胶。湿凝胶经溶剂交换、超临界干燥、高温炭化等处理得到TiO2/C杂化气凝胶。利用X射线衍射、透射电子显微镜及N2吸附-脱附等方法对气凝胶的晶型结构、微观形貌及孔结构分布进行表征。通过对亚甲基蓝的光催化降解考察样品的光催化性能。结果表明,钛源前驱体种类及其浓度对亚甲基蓝的光催化降解效率影响较大。相对于以钛酸四丁酯为钛源制备的TiO2/C杂化气凝胶,以四氯化钛为钛源制备的TiO2/C杂化气凝胶对亚甲基蓝的光催化效果更好。以四氯化钛为钛源,以TiO2计的钛源与碳源质量之比为0.38时所制样品具有最佳的性能,其最大平均孔径为7.8nm,最大介孔孔容为0.40 cm3/g,180 min对亚甲基蓝光催化降解率达99.6%。     

纳米ZnO/Zn/CNT多孔复合结构的制备及其对亚甲基蓝的无光催化降解

以碳纳米管(CNTs)为基础材料,聚甲基丙烯酸甲酯(PMMA)为造孔剂,构筑多孔结构,并将水解反应所得的氧化锌/锌复合纳米颗粒附着在孔隙结构中,制得氧化锌/锌/碳纳米管多孔复合结构,氧化锌纳米棒直径约30~60nm,长径比可达40。对复合结构的微观结构及成分表征显示,制备ZnO/Zn/CNT多孔复合结构的过程中,无杂质生成,氧化锌晶体结构也没有发生变化。多孔复合结构对模拟污染物的暗室催化降解研究结果显示,复合结构催化降解亚甲基蓝时起主要作用的是ZnO纳米棒,在多孔结构中受力变形产生电子空穴对,在无光条件下降解有机污染物,且孔径越大、水流冲击力越强,对亚甲基蓝的催化降解效果越好。     

La掺杂TiO2介孔微球的超声水热合成和光催化性能

以钛酸四丁酯为钛源、硝酸镧为镧源、十二胺为模板剂,采用超声?水热法合成了La3+掺杂介孔TiO2微球,并利用XRD、XPS、TEM、BET、UV-Vis、IR、FL等手段表征了材料的结构、形貌、比表面积、孔径分布及光学性能.研究结果表明,适量La3+离子掺杂不仅能使介孔TiO2晶粒细化,比表面积增大,荧光强度减弱.La3+/TiO2的光吸收边红移,并具有比商业P25更好的光催化活性,其中介孔La3+/TiO2(2.0at%)的比表面积和平均孔径分别为132.7 m2/g和8.67 nm,光催化降解初始浓度为40 mg/L的亚甲基蓝溶液120 min时,其降解率达到98.5%,表现出最强的光降解能力.     

N掺杂TiO2/SiO2双层中空微球的制备及可见光光催化活性研究

以阳离子PS为模板,正硅酸乙酯和钛酸丁酯为前驱体,三乙胺为氮源,采用溶胶-凝胶法,通过层层静电自组装制备了N掺杂TiO2/SiO2 (N-TS)复合微球,并经高温焙烧得到具有介孔结构的N-TS双层中空微球.采用Zeta-plus激光粒度及电位仪、SEM、XRD、UV-Vis等对微球的结构进行表征,以亚甲基蓝为目标污染物,考察了N-TS双层中空微球的可见光光催化活性.结果表明,通过SiO2和TiO2的交替包覆形成了双壳层结构,保持了中空微球完整的球形形貌;N的掺入有效拓宽了TiO2光响应范围且在可见光区域吸收明显增强,在掺N量为n(N) /n(Ti)=10、500℃焙烧得到的双层中空微球可见光催化活性最优,2h内亚甲基蓝几乎完全降解,同时中空微球在重复使用过程中依然能保持较高的可见光光催化活性.     

Facile synthesis and enhanced photocatalytic activity of hierarchical porous ZnO microspheres

In this paper, hierarchical porous ZnO microspheres were successfully synthesized by calcining the microspheric zinc hydroxide carbonate (ZHC) precursor, which were the precipitate products of a hydrothermal reaction by zinc nitrate hexahydrate and urea in the presence of trisodium citrate. The as-prepared ZnO microspheres with diameters of 4-5 μm were assembled by numerous porous nanosheets which had the uniform thickness of about 10 nm. The photocatalytic activity of the ZnO microspheres was evaluated by photodegradation reaction of methylene blue (MB). The as-prepared ZnO microspheres exhibited a significantly enhanced photocatalytic activity than commercial ZnO and TiO₂. This was mainly attributed to the larger specific surface area and stability against aggregation.     

Mesoporous nanocrystalline ZnO microspheres by ethylene glycol mediated thermal decomposition

Zinc oxide (ZnO) nanostructures with various morphologies have been fabricated in literature owing to their potential applications in various emerging fields. In this study, we report a facile, one-step gram-scale synthesis of nanocrystalline mesoporous ZnO microspheres by thermal decomposition of zinc acetate dihydrate in ethylene glycol at 250?°C for 12?h. The average size of the hollow microspheres is found to be 3.01?±?0.52?µm, which are formed by loosely bonded nanocrystallites with average sizes of 17?±?4?nm. We propose a formation mechanism for the mesoporous microspheres, Ostwald ripening of spherical-like nanocrystallites, on the basis of the results obtained by different synthesis durations. We also report the possibility of tuning the morphologies of the obtained ZnO by simply modifying the thermal decomposition solution, where porous ZnO nanoplates are obtained when a mixture of ethylene glycol and water is used and ZnO nanorods with aspect ratios of ～3 are synthesized by using diethylene glycol. ZnO nanowires with lengths up to several microns are fabricated when no solvent is used, i.e. thermal decomposition in air atmosphere. Microstructural and phase characterizations of the samples are conducted by using a field-emission gun scanning electron microscope and X-ray diffractometer. Performances of the obtained nanocrystalline mesoporous ZnO microspheres in photocatalytic degradation of Rhodamine B and as active anode materials in lithium-ion batteries are also presented.     

中空ZnO微球的制备及其光催化性能

以葡萄糖和醋酸锌为原料,采用模板法制备中空ZnO微球。并对所制样品进行表征,讨论了碳微球与醋酸锌物料比、煅烧温度、煅烧时间对ZnO催化剂光催化活性的影响。结果表明:在碳微球与醋酸锌物料比为1∶2、煅烧温度500℃、煅烧时间2h条件下,所制备的中空ZnO微球直径约为3~5μm,六方晶系结构,具有较好的光催化活性。     

Synthesis of titania microspheres with hierarchical structures and high photocatalytic activity by using nonanoic acid as the structure-directing agent

The titania, as the heterogeneous photocatalyst, has attracted much attention in attempts to eliminate pollutants, especially organic compounds in water and air. In this study, the titania microspheres with hierarchical structures were prepared by a combined sol–gel and solvothermal method. The X-ray powder diffraction (XRD) result indicated that the synthesized titania microspheres were of anatase phase. Field-emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM) showed that the microspheres with well-dispersity had an average diameter of 651 nm and were composed of nanoparticles with about 20 nm in diameter. The Brunauer–Emmett–Teller (BET) results showed that the microspheres possessed high surface areas and lots of mesopores. Further study indicated that the synthesized titania microspheres exhibited high photocatalytic activity and had an important advantage over the commercial P25.     

Synthesis of 3D micro- and nano-hierarchical structure InVO4 porous microspheres with improved visible-light photocatalytic activities

Three-dimensional (3D) hierarchical structure InVO₄ porous microspheres were fabricated by a hydrothermal method with the assistance of cetyltrimethyl-ammonium bromide (CTAB). X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, adsorption analyzer, diffuse refection spectroscopy, UV–Vis spectroscopy, and photoluminescence spectroscopy were adopted to analyze the structure–property relationship of samples, and the formation mechanism was also discussed. The results show that the concentration of CTAB solution has important influence on the grain size, crystal structure, and morphology of as-synthesized InVO₄ samples, thus affecting the optical property and photocatalytic activity. When the concentration of CTAB solution is 1 wt%, we can obtain perfect 3D hierarchical porous microspheres. Such microspheres with diameter size about 2–5 μm are assembled by numerous nanocrystals, and exhibit an enhanced photocatalytic activity in the degradation of Rhodamine B under visible light irradiation. Moreover, Oswald ripening and self-assembly aggregation are presumed to play an important role in the formation of these 3D hierarchical structure InVO₄ porous microspheres.     

Photocatalytic behaviors of porous ZnO hierarchical structures fabricated via a precursor-pyrolyzing route

It is of significance to develop porous ZnO photocatalysts with high activity. In this paper, three kinds of hierarchical ZnO porous structures were fabricated by a precursor transformation of hierarchical Zn₅(CO₃)₂(OH)₆ structures synthesized in the zinc salts and urea aqueous solution. The microstructure characterization demonstrates that the obtained ZnO materials are porous structure and quasi-single-crystal nature. The solid UV–vis and PL spectra indicate that the porous ZnO with different morphologies have similar photoabsorption ability but different ratioes of green-to-UV emission, respectively. These porous ZnO samples with different structures exhibit different photocatalytic efficiency. More importantly, the photocatalytic activity of porous ZnO fabricated by the precursor-pyrolyzing method is inversely proportional to the content of surface defects under other influence factors comparable. This result inconsistent with references was also discussed.     

Hydrothermal growth of symmetrical ZnO nanorod arrays on nanosheets for gas sensing applications

The hierarchical ZnO nanostructures with 2-fold symmetrical nanorod arrays on zinc aluminum carbonate (ZnAl-CO₃) nanosheets have been successfully synthesized through a two-step hydrothermal process. The primary nanosheets, which serve as the lattice-matched substrate for the self-assembly nanorod arrays at the second-step of the hydrothermal route, have been synthesized by using a template of anodic aluminum oxide (AAO). The as-prepared samples were characterized by XRD, FESEM, TEM and SAED. The nanorods have a diameter of about 100 nm and a length of about 2 μm. A growth mechanism was proposed according to the experimental results. The gas sensor fabricated from ZnO nanorod arrays showed a high sensitivity to ethanol at 230°C. In addition, the response mechanism of the sensors has also been discussed according to the transient response of the gas sensors.     

Ultrathin ZnO nanostructures synthesized by thermal oxidation of hexagonal Zn micro/nanostructures

Ultrathin (<5 nm) ZnO nanobelts, as well as porous nanotubes/nanosheets were successfully synthesized via a very simple process: thermal oxidation of hexagonal Zn micro/nanostructures in a tube furnace in 50 sccm N2 flow. The ZnO nanobelt clusters were largely grown from the (0001) end surface of the Zn nanoprisms at 300 degrees C. The porous nanotubes and nanosheets were formed on the downstream substrate by 370-400 degrees C thermal oxidation of Zn films in low pressure. These structures are related to the anisotropic oxidation of Zn and differences of melting point between Zn and ZnO. We propose that the ultrathin nanobelts were formed in a vapor-liquid-solid process while the ultrathin nanotubes and nanosheets were formed via a vapor-solid-resublimation process. The structure of the nanostructures was characterized by transmission electron microscopy. The ultrathin mesoporous nanotubes and nanosheets have been found to possess rich surface defects. These structures may have potential applications in gas sensors, catalysts and hydrogen storage due to their large specific surface area.     

Large-scale synthesis of hexagonal cone-shaped ZnO nanoparticles with a simple route and their application to photocatalytic degradation

We report the large-scale synthesis of hexagonal cone-shaped ZnO nanoparticles by the esterification between zinc acetate and alcohol. The morphology of the ZnO nanoparticles was investigated by transmission electron microscopy, selected area electron diffraction and scanning electron microscopy measurements. The synthesized ZnO nanoparticles are single-crystalline with hexagonal phase and show a strong UV emission at −378 nm due to the excellent crystallinity of particles. A possible formation mechanism of the hexagonal cone-shape structure is proposed. Furthermore, the as-prepared ZnO particles exhibit high photocatalytic activity for the photocatalytic degradation of Rhodamine B, indicating that the ZnO nanostructure is promising as a semiconductor photocatalyst.     

Clew-like hierarchical ZnO nanostructure assembled by nanosheets as an efficient photocatalyst for degradation of azure B

In this study, hierarchical ZnO nanostructure assembled by nanosheets was synthesized via a facile and rapid ultrasound assisted route without any surfactant or template. The phase structure, morphology and optical property of the ZnO sample were investigated by XRD, FT-IR, SEM, and UV–Vis spectroscopy. Nitrogen sorption was also studied to determine the specific surface area and the pore size distribution. The ZnO sample was hexagonal pure phase of hierarchical clew-like microspheres consisting of nanosheets with average thickness and specific surface area of 50 nm and 41 m² g^?1, respectively. Synthesized ZnO was applied for the photocatalytic degradation of an organic dye, azure B as a pollutant model under UV irradiation. The effects of several parameters including dye concentration, catalyst dosage, pH, and irradiation time on photocatalytic degradation have been studied. The results indicated hierarchical ZnO has potential application for degrading of organic pollutants. Hydroxyl radicals were found to be main reactive species in this photodegradation process.