超临界流体干燥法制备TiO2/ Fe2O3 和TiO2/ Fe2O3/ SiO2 复合纳米粒子及光催化性能

以TiCl₄ 、Fe (NO₃ )₃·9H₂O 和Na₂SiO₃19H₂O 为原料, 采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级TiO₂/ Fe₂O₃ 和TiO₂/ Fe₂O₃/ SiO₂ 复合光催化剂。以光催化降解苯酚对所得催化剂的催化活性进行了评价。结果表明, 纳米TiO₂/ Fe₂O₃ 复合粒子与单组分TiO₂ 比较, 复合粒子光催化活性高于单组分的TiO₂, 6h 苯酚降解率高达95.9 %。SiO₂ 的加入可以抑制纳米粒子粒径的长大和晶相的转变, 增强TiO₂ 纳米粒子的热稳定性。复合光催化剂中Fe₂O₃ 最佳掺入量为0.06 %, SiO₂ 最佳掺入量为10 %(摩尔分数) 。并用XRD、TEM 和FTIR 等手段进行了表征。TiO₂ 以锐钛矿型形式存在, SiO₂ 以无定性形式存在。比较了不同制备方法制得的TiO₂/ Fe₂O₃ 复合光催化剂, 得出超临界干燥法制备的光催化剂具有粒径小、比表面积大、分散性好、光催化活性高等特点。采用超临界流体干燥可直接得锐钛型纳米复合光催化剂。     

NiCo2O4/氧化石墨烯复合材料制备与电化学性能研究

为了研究NiCo₂O₄/氧化石墨烯(NiCo₂O₄/GO)复合材料的电化学性能,本文通过先水热合成前驱体再煅烧的方法制备了一系列NiCo₂O₄/GO复合材料.利用X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学方法对其进行物理表征,其中以GO质量浓度为1 mg/mL悬浊液制备出的NiCo₂O₄ /GO-3复合材料呈类海胆状结构.在1 M KOH水溶液中使用循环伏安法、恒电流充/放电法和交流阻抗法研究了NiCo₂O₄/GO复合材料电化学性能.研究表明,与纯NiCo₂O₄相比,制备的NiCo₂O₄ /GO复合材料的比容量和赝电容性能均有明显提高,这主要是由于NiCo₂O₄ /GO复合材料中NiCo₂O₄与GO纳米片的相互作用形成的高孔隙率复合结构;NiCo₂O₄ /GO-3复合材料在电流密度为0.5~3.0 A/g时,比电容超过650 F/g,具有良好的倍率性能和高比容量.采用本文方法合成的NiCo₂O₄/GO复合材料,既提高了其倍率性能又保证了高比容量,是一种良好的超级电容器电极材料.     

5A分子筛载CuO对甲基橙的催化湿式过氧化氢氧化

以三水硝酸铜和5A分子筛为原料,采用湿法浸渍法制备了CuO-5A催化剂,采用扫描电镜、X射线衍射仪和红外光谱仪对其进行分析表征,并将其用于处理甲基橙模拟废水。考察材料种类(5A+H₂O₂,20%CuO-5A+H₂O₂,H₂O₂)、铜负载量、pH值、催化剂投加量、温度等因素对催化效果的影响,并测定催化剂的稳定性,同时采用准一级动力学模型进行拟合分析。结果表明,CuO已成功负载在5A分子筛表面,采用20%的CuO-5A对甲基橙的催化湿式氧化效果最好。在甲基橙初始浓度为50 mg/L、材料投加量为0.6 g、pH值为2、温度为70 ℃条件下,第一次、第二次和第三次使用的CuO-5A在60 min时对甲基橙的转化率分别为97.9%、92.3%和90.5%。不同温度下CuO-5A对甲基橙的催化湿式氧化行为可用准一级动力学方程来描述,拟合曲线展示了两个线性阶段,其中第二阶段活化能为50.35 kJ/mol。     

过硫酸氢盐催化材料(Co3O4/ACF)的制备及应用

通过改变溶剂热法和水热法中材料的配比和温度制备了18种四氧化三钴/活性炭纤维(Co₃O₄/ACF)复合材料,并将这些复合材料用于催化过一硫酸盐(PMS)降解染料橙黄Ⅱ。考察了制备材料的配比(Co²⁺和ACF)和温度对制得的Co₃O₄/ACF复合材料催化降解橙黄Ⅱ效率的影响,并采用X射线衍射仪、扫描电镜等对复合材料的元素组成和形貌进行了表征。结果表明:水热法制得的复合材料催化性能好,3 min内可完全降解100 mg/L橙黄Ⅱ。从表征结果可见,水热法能更有效地使Co₃O₄颗粒以纳米尺寸分散负载在ACF上。材料的配比对产品的催化降解效率无显著影响,温度对水热法制得的产品的催化降解效率影响不大。水热法在320 ℃条件下煅烧制得的复合材料催化性能好且ACF能基本保持结构完整,Co负载量约为17.2 mg/g。水热法制备的Co₃O₄/ACF复合材料循环利用性能优于溶剂热法制得的材料,在循环使用四次后,28 min内橙黄Ⅱ降解效率仍能达到99%。其高效降解与Co₃O₄/ACF和溶解态Co²⁺的催化作用均有关。正交试验表明,降解过程中时间对降解效果的影响最大,其次是PMS的浓度,催化材料的加入量对降解效率无明显影响。因此,在复合材料应用中,应保证充足的降解时间,并适当提高PMS的浓度。     

壳聚糖-CdS复合纳米粒子对甲基橙的光催化降解作用

用反相微乳液法制备了壳聚糖-CdS复合纳米粒子,并考察了复合纳米粒子用量、光照条件和溶液pH值等因素对光催化降解甲基橙的影响.结果表明:在100 mL质量浓度为20 mg/L的甲基橙溶液中加入0.30 g复合纳米粒子,可以达到较好的光催化降解效果;甲基橙在光催化降解过程中最大吸收波长464 nm处的吸收峰迅速减弱,并最终消失,且在258 nm和455 nm处出现了新的吸收峰,说明甲基橙发生了降解;溶液pH值对光催化降解甲基橙有一定的影响,在弱酸性条件下降解效率较高;复合纳米粒子比普通CdS降解效率高,2 min时高出50%,400 min时高出21.3%.初步提出了复合纳米粒子光催化降解机理,复合纳米粒子的吸附作用是光催化降解作用的前置步骤.     

共沉淀法合成近零膨胀ZrW2O8/ZrO2复合陶瓷的致密化

采用化学共沉淀法合成前驱体,经1150℃ 烧结3.5 h得到近零膨胀26 wt% ZrW₂O₈/ZrO₂复合陶瓷,并利用X射线衍射仪、扫描电镜和热膨胀仪研究了原料中加入Al(NO₃)₃·9H₂O对26 wt% ZrW₂O₈/ZrO₂复合陶瓷的相组成、致密度和热膨胀性能的影响。研究结果表明,少量添加Al(NO₃)₃·9H₂O可有效提高复合材料致密度,所得复合陶瓷的组分仍为立方结构的α-ZrW₂O₈和单斜的m-ZrO₂,其中添加2.21 wt% Al(NO₃)₃·9H₂O的复合材料的致密度达到理论密度的98.67%,且对复合陶瓷的热膨胀性能影响不大。其促进致密化机制为晶界处低熔点液相物质Al₂(WO₄)₃提高了复合材料的烧结性能,消除气孔促进致密化。     

可见光响应RGO/TiO_2复合材料制备及性能研究

以内蒙古兴和县天然石墨为前驱体,用改进的Hummers法制备氧化石墨烯(GO),并以硫酸钛[Ti(SO4)2]为钛源,采用水热法制备了系列还原氧化石墨烯(RGO)/二氧化钛(TiO_2)复合材料,采用XRD、SEM、FT-IR及UV-Vis等对样品进行测试,并以甲基橙溶液为目标污染物评价其可见光光催化性能。结果表明:制得的RGO/TiO_2复合材料中TiO_2均以锐钛矿型存在,颗粒尺寸7nm左右,光响应范围扩至可见区,具有较高的可见光光催化活性;当GO掺杂量为0.10g时制得的复合材料,在氙灯照射10min后对甲基橙的降解率可达88.41%,照射30min时的降解率可达到96%以上。     

还原氧化石墨烯/SnS_2纳米复合物的制备与可见光光催化性能

以氧化石墨烯(GO)和SnCl_4·5H_2O为前驱体,通过水热法制备了SnS_2/还原氧化石墨烯(RGO)复合材料。用X射线衍射(XRD)、扫描电镜(SEM)、拉曼光谱和紫外-可见(UV-Vis)吸收光谱表征了所制备的样品。在可见光(λ≥420nm)光照下光催化降解甲基橙水溶液来检测SnS_2/RGO复合物的光催化活性。结果表明:所制备的SnS_2/RGO复合物表现出增强的可见光光催化活性,其中,含1%(wt,质量分数,下同)石墨烯的复合光催化剂活性最好。SnS_2/RGO复合物光催化活性的增强是由于石墨烯是优秀的电子受体和传输体,它减少了光生载流子的复合,从而提高了光催化活性。     

WO_3-TiO_2纳米材料的制备及其光催化性能

采用溶胶-凝胶法制备WO3-TiO2纳米复合材料,并用透射电镜和X射线衍射对所制备材料进行表征和分析。以WO3-TiO2纳米材料为光催化剂对甲基橙进行光催化降解处理,研究WO3的掺杂量、煅烧温度、光照时间等因素对甲基橙降解率的影响。结果表明:在紫外灯照射下,使用w(WO3)=3%、550℃下煅烧得到的WO3-TiO2纳米复合粉体0.02 g,甲基橙溶液20 mL(ρ=5 mg/L,pH=4),光催化3 h后,甲基橙降解率达到94.93%。     

镁酞菁/PHBV催化薄膜的制备及光催化性能研究

将四氨基镁酞菁(MgPc)负载到PHBV上制备复合催化薄膜(MgPc/PHBV)。采用XRD、FT-IR、TGDTA和UV-Vis DRS等表征技术对MgPc/PHBV的结构和性质进行表征。结果表明,MgPc和PHBV之间可能通过物理作用结合;MgPc的加入降低PHBV的结晶度;并且将PHBV的分解温度提高20℃。基于UV-Vis DRS的测试表明MgPc/PHBV薄膜具有可见光催化活性。此外,MgPc/PHBV光催化降解有机污染物甲基橙的结果表明,光照、MgPc/PHBV和H_2O_2同时存在时才能催化氧化甲基橙;光照160 min后,甲基橙剩余率为0.0%,甲基橙完全被降解。光催化氧化反应中羟基自由基发挥着关键作用。     

Preparation of nitrogen doped TiO2 photocatalyst by oxidation of titanium nitride with H2O2

Nitrogen doped anatase TiO₂ (N-TiO₂) were prepared by hydrothermally treating TiN with H₂O₂. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV-vis diffuse reflectance spectrum (DRS), Fourier transform infrared spectra (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques. The results confirmed that the hydrothermal oxidation is an effective method to prepare N-doped TiO₂ anatase. The nitrogen concentration in TiO₂ could be controlled by the concentration of H₂O₂ solution. Photocatalytic degradation of methyl orange (MO) was carried out under visible light and UV-visible light irradiation, respectively. The as-prepared optimal N-TiO₂ showed higher photocatalytic activity than N-P25 and P25, and exhibited excellent reusability.     

Heterostructured Fe3O4/Bi2O2CO3 photocatalyst: Synthesis,characterization and application in recyclable photodegradation of organic dyes under visible light irradiation

Heterostructured Fe₃O₄/Bi₂O₂CO₃ photocatalyst was synthesized by a two-step method. First, Fe₃O₄ nanoparticles with the size of ca. 10 nm were synthesized by chemical method at room temperature and then heterostructured Fe₃O₄/Bi₂O₂CO₃ photocatalyst was synthesized by hydrothermal method at 180 °C for 24 h with the addition of 10 wt% Fe₃O₄ nanoparticles into the precursor suspension of Bi₂O₂CO₃. The pH value of synthesis suspension was adjusted to 4 and 6 with the addition of 2 M NaOH aqueous solution. By controlling the pH of synthesis suspension at 4 and 6, sphere- and flower-like Fe₃O₄/Bi₂O₂CO₃ photocatalysts were obtained, respectively. Both photocatalysts demonstrate superparamagnetic behavior at room temperature. The UV–vis diffuse reflectance spectra of the photocatalysts confirm that all the heterostructured photocatalysts are responsive to visible light. The photocatalytic activity of the heterostructured photocatalysts was evaluated for the degradation of methylene blue (MB) and methyl orange (MO) in aqueous solution over the photocatalysts under visible light irradiation. The heterostructured photocatalysts prepared in this study exhibit highly efficient visible-light-driven photocatalytic activity for the degradation of MB and MO, and they can be easily recovered by applying an external magnetic field.     

Enhancement of photocatalysis performance of CdIn2S4/g-C3N4 heterojunction by H2O2 synergism

A highly efficient binary CdIn₂S₄/g-C₃N₄ heterojunction photocatalyst was synthesized by a simple wet impregnation method. Photocatalytic system based on the synergistic action of binary CdIn₂S₄/g-C₃N₄ heterojunction and H₂O₂ was proposed to improve the degradation effect of dyes. The photocatalytic activity was evaluated by the degradation of methyl orange(MO) under visible light irradiation. The results demonstrated that contrasted to pure g-C₃N₄, the synthesized heterojunction can significantly improve the photocatalytic activity. After 120 min of irradiation by visible light, the photocatalytic efficiency of MO degradation of 7CIS/CN was 3.13 times higher than that of g-C₃N₄. When 60 mM H₂O₂ was added on this basis, the photocatalytic efficiency increased from 93.81 to 99.40%. The improvement of photocatalytic activity is attributed to the formation of binary CdIn₂S₄/g-C₃N₄ heterojunction to promote the transfer of photogenerated electron-hole pairs, and an appropriate amount of H₂O₂ as an electron trap further reduced the recombination rate of photogenerated electron-hole pairs. Active species capture experiments showed that ·O₂^? are the main active substances. Subsequently, the mechanism of photocatalytic degradation was proposed. This work provided a new efficient strategy for the degradation of industrial dye wastewater.

     

Graphene oxide (GO) doped CeO2 as potential enhancer of methyl orange degradation

In this article, a simple method for the synthesis of Graphene Oxide-Cerium oxide (GO/CeO₂) is carried out. The prepared sample was characterized in detail, such as scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman, Brunauer-Emmett-Teller technology N₂ adsorption-desorption analysis (BET), photoluminescence (PL) and UV-visible diffuse reflectance spectroscopy (DRS). It was indicated that GO was successfully incorporated into CeO₂. The photocatalytic mechanism of GO/CeO₂ was also explained. The MO solution catalyzed by CeO₂ and GO/CeO₂ was analyzed by a UV-visible spectrometer. The efficiency of GO/CeO₂ degrading methyl orange (MO) is improved from 50% to 87% compared to pure CeO₂ under the visible light. GO/CeO₂ exhibited better photocatalytic performance than CeO₂, which indicated GO doping improved the photocatalytic capacity of the CeO₂ catalyst. It may have potential applications in addressing environmental wastewater.     

Sulphur,nitrogen-doped TiO2/graphene oxide composites as a high performance photocatalyst

Sulphur (S), nitrogen (N)-doped TiO₂/graphene oxide (GO) composites were environmentally friendly synthesised using thiourea (CS(NH₂)₂) as a binary-element doping reagent by a simple colloidal blending method. The S, N-doped TiO₂/GO composites show higher photocatalytic degradation rates on methyl orange (MO) compared to TiO₂. The average value of k (the apparent rate constant) for the S, N-doped TiO₂/5%GO (k?=?0.035?min^?1) was found to be eight times higher than that of TiO₂ grown in solution (k?=?0.0038?min^?1) and four times higher than that of P25 (k?=?0.008?min^?1). The investigation showed that the contribution of GO to the high photocatalytic activities of the composites come from its high specific surface area, oxygen-containing functional groups and large aromatic domains that were inclined to be bound by conjugated MO molecules via π–π stacking. The doping of S and N can increase the numbers of photo-generated electrons and holes, which produce more charge carriers to form reactive species, and thus promote the degradation of MO. This work could offer a route to improve the photocatalytic activities of TiO₂ and facilitate their application in reality.     

Enhanced Photocatalytic Property of Reduced Graphene Oxide/TiO2 Nanobelt Surface Heterostructures Constructed by an In Situ Photochemical Reduction Method

A facile method is proposed to assemble graphene oxide (GO) on the surface of a TiO₂ nanobelt followed by an in situ photocatalytic reduction to form reduced graphene oxide (rGO)/TiO₂ nanobelt surface heterostructures. The special colloidal properties of GO and TiO₂ nanobelt are exploited as well as the photocatalytic properties of TiO₂. Using water–ethanol solvent mixtures, GO nanosheets are tightly wrapped around the surface of the TiO₂ nanobelts through an aggregation process and are then reduced in situ under UV‐light irradiation to form rGO/TiO₂ nanobelt surface heterostructures. The heterostructures enhance the separation of the photoinduced carriers, which results in a higher photocurrent due to the special electronic characteristics of rGO. Compared to TiO₂ nanobelts, the rGO/TiO₂ nanobelt surface heterostructures possess higher photocatalytic activity for the degradation of methyl orange and for the production of hydrogen from water, as well as excellent recyclability, with no loss of activity over five cycles.     

Photodecomposition effects of graphene oxide coated on TiO2 thin film prepared by electron-beam evaporation method

Morphological, structural and photocatalytic properties of graphene oxide (GO)/TiO₂ thin-film deposited on quartz substrate were investigated. The TiO₂ film was prepared by electron-beam evaporation and the GO film by spin coating method. The photocatalytic activities of the GO/TiO₂ film were evaluated by photodecomposition of methylene blue. There was synergistic effect between TiO₂ and GO which causes a rapid photo-induced charge separation and the reduction of the recombination of electron-hole pairs under the UV-visible light irradiation. GO on TiO₂ film also promotes the properties of adsorption of the dye, photon scattering probability, and interacting surface area. As a result, it leads to the enhancement of the efficiency of the photodegradation in GO/TiO₂ film.     

Preparation and photocatalytic activity of novel efficient photocatalyst Sr2Bi2O5

A novel visible-light-driven photocatalyst of Sr₂Bi₂O₅ is prepared by solid-state reaction at 780 °C. The optical band gap of Sr₂Bi₂O₅ is determined to be 2.87 eV by UV-Vis diffuse reflectance spectroscopy. Under both UV and visible-light irradiation, the photocatalytic activity for degrading methyl orange (MO) over Sr₂Bi₂O₅ is higher than those over BiVO₄, and SrBi₂O₄. The relationships between the photocatalytic properties of Sr₂Bi₂O₅, SrBi₂O₄, and BiVO₄ and their crystal structures are discussed. Among Sr₂Bi₂O₅, SrBi₂O₄, and BiVO₄, the higher photocatalytic activity of Sr₂Bi₂O₅ is ascribed to its higher level of distortion of the metal-oxygen polyhedra, and the lower packing factor degree.     

Fabrication of a 12-tungstophosphate and cadmium oxide composite film and its properties

A multilayer composite film of the 12-tungstophosphate H₃[PW₁₂O₄₀]³⁻ (PW₁₂) and cadmium oxide nanoparticles (CdO) was fabricated on quartz and silicon by the layer-by-layer (LBL) self-assembly method. The film was characterized by UV–vis spectroscopy, atomic force microscopy (AFM) and luminescence spectra. The proposed composite film exhibits higher photocatalytic activity toward methyl orange (MO) solution at pH 3.5, compared to single PW₁₂ and CdO films. The degradation rate was affected by initial concentration of PW₁₂, pH value of MO solution, inorganic ions concentration and type in MO solution. In addition, the composite film displays luminescent property and reversible electrochromic property with fast response time.