ZnO:Cd纳米棒的制备及其光催化降解性能研究

采用水热法制备了ZnO和不同Cd掺杂浓度的ZnO:Cd纳米棒。通过x射线衍射仪、扫描电子显微镜、紫外-可见-近红外分光光度计和拉曼光谱对ZnO:Cd纳米棒的结构和光学特性进行了系统研究。结果显示,样品为一维纳米棒结构,Cd的掺杂可以减小ZnO纳米棒的晶粒尺寸和光学带隙。利用分光光度计检测ZnO:Cd纳米棒对偶氮结构染料(甲基橙溶液)的光催化降解效率,结果表明Cd掺杂可以改善ZnO的光催化性能,掺杂浓度为16%时ZnO:Cd纳米棒对甲基橙溶液的光催化降解效率最高。     

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。     

介孔RGO/TiO2复合光催化材料的制备及光催化性能

采用溶胶-凝胶法, 以氧化石墨烯(GO)、钛酸四丁酯(TBT)为原料, 聚乙烯吡咯烷酮(PVP)为结构引导剂, 柠檬酸为水解抑制剂和表面活性剂原位合成不同GO含量的介孔氧化石墨烯/二氧化钛复合材料(GO/TiO₂), 再经过紫外灯辐照还原获得介孔还原氧化石墨烯/二氧化钛复合材料(RGO/TiO₂)。通过X射线衍射(XRD)、透射电镜(TEM)、比表面积(BET)、紫外-可见漫反射(UV-Vis DRS)和荧光光谱(PL)对样品进行分析表征, 研究了RGO/TiO₂的形貌、孔径分布情况, RGO的引入对光生电子-空穴对寿命、吸附性能、光催化性能的影响。分别在紫外光和太阳光条件下评价了复合材料的光催化性能, 并在紫外光条件下, 对催化剂进行了多次回收循环测试。测试结果表明: TiO₂均匀地生长于RGO表面, RGO/TiO₂为介孔材料; RGO的引入可以有效地抑制光催化剂中光生-电子空穴对的复合, 提高吸附性能和光催化性能, 7wt%RGO/TiO₂显示出对甲基橙的最佳吸附效果; 5wt%RGO/TiO₂对甲基橙具有最佳光催化效果和稳定的催化活性, 经过4次循环后, 紫外光照50 min, 对甲基橙的降解率仍能达到首次降解效率的90%以上。     

ZnO/TiO2复合材料的制备及其光学特性

采用水热法在锌片上制备出棒状ZnO,将TiO2溶胶旋涂在棒状ZnO上得到ZnO/TiO2新型复合材料。利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)及UV-Vis漫反射(DRS)等研究样品的微观形貌、晶型结构、光学特性。研究表明:375℃焙烧后,TiO2附着在ZnO纳米棒表层,随着溶胶旋涂层数的增加,其形貌呈现出多维花状结构。通过光催化降解甲基橙模拟废水考察其光催化性能,实验结果表明,ZnO/TiO2复合半导体的多维结构使其对紫外-可见光吸收增强,对甲基橙模拟废水(20mg/L)的降解率高达94.7%,具有优异的光催化性能。     

水热法制备N-TiO_2/RGO复合材料及光催化性能研究

采用一步水热法制备氮掺杂负载石墨烯(RGO)的二氧化钛(TiO_2)复合光催化材料(N-TiO_2/RGO),对样品进行XRD、SEM、UV-Vis等表征并以甲基橙为目标降解物进行可见光光催化活性测试。结果表明:N-TiO_2/RGO比同条件下制得的N-TiO_2和TiO_2/RGO具有更好的可见光光催化性能,可见光下照射5h,对甲基橙的降解率可达到95%。     

N掺杂纳米ZnO/聚氯乙烯复合材料的制备和光催化性能

制备了N掺杂纳米ZnO/聚氯乙烯复合材料。红外光谱和紫外可见漫反射吸收光谱的结果表明,这种复合材料在紫外和可见光区均有很强的吸收。研究了复合材料光催化降解甲基橙的效率,结果表明:聚氯乙烯的复合减少了电子-空穴的复合几率,也拓宽了整个体系的可见光谱响应范围,提高了复合材料在可见光照射下的光催化性能。     

ZnS/ZnO纳米片组装的多孔微球的制备及光催化性能研究

将水热法制备的ZnS纳米球500℃下保温2h制备出由ZnS、ZnO纳米片组装的多孔微球。利用扫描电子显微镜、X射线衍射仪、透射电子显微镜、紫外-可见近红外分光光度计和紫外-可见分光光度计等对样品的形貌、结构和光学性能进行了表征。以甲基橙(MO)的光催化降解为目标反应,评价其光催化活性。ZnS/ZnO异质结材料的带隙明显窄于ZnO,光催化活性得到提高;经60 min紫外光照射后,ZnS/ZnO异质结催化剂对MO的降解率为76%。最后分析和探讨了异质结催化剂的光催化机理。     

TiO2负载ZnO纳米棒的制备及其光催化性能

采用水热法制备ZnO纳米棒,将TiO2溶胶高速旋涂在ZnO纳米棒的表面,得到TiO2/ZnO复合半导体。通过扫描电子显微镜(SEM)、X射线衍射(XRD)及UV-Vis漫反射等研究样品的表面形貌、晶型结构及光学特性。结果表明:375℃高温焙烧后,TiO2生长成颗粒状,均匀负载在ZnO纳米棒的表面,样品对紫外-可见光的吸收增强。以甲基橙溶液为模拟废水在紫外光辐照下的降解率来评价样品的光催化性能,结果显示,两种半导体复合以后,对光的利用率提高,对甲基橙模拟废水的降解率高于单一半导体。     

低温液相法制备掺铁氧化锌及其光催化活性

探索低温液相法合成掺Fe的Fe∶ZnO,Fe∶Zn摩尔比为0.01~0.03,通过调整氢氧化钠的量来控制氧化锌的微观形貌,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱仪(EDS)、紫外-可见光谱(UV-vis)、荧光光谱(PL)对所合成的材料进行表征,采用紫外照射测试样品对甲基橙的光催化降解率。结果表明:在80℃水溶液环境下低温合成及随后干燥,成功制备出了掺杂不同Fe含量的Fe∶ZnO纳米片,所获得的样品均为纤锌矿结构,结晶度高。随着Fe掺杂量的增加,样品的紫外-可见吸收光谱红移,在可见光区吸收增大,带隙减小;适量的Fe掺杂可以降低样品光生电子与空穴的复合率,提高样品光催化性能。掺杂Fe量为1.5%的Fe∶ZnO的样品光催化降解甲基橙的效率最高,紫外光照反应5h后对甲基橙的光催化降解率相对于纯的ZnO提高了43.8%。     

Doping effects of Co(2+) ions on ZnO nanorods and their photocatalytic properties

A series of Zn(1-x)Co(x)O nanorods with dopant content ranging from x = 0.00 to 0.10 was prepared by a wet chemical method. All Zn(1-x)Co(x)O samples were investigated by x-ray diffraction, transmission electron microscopy, energy-dispersion x-ray line mapping analysis, and UV-visible absorption spectroscopy. It was found that Co(2+) ions were homogeneously substituted for Zn(2+) ions in ZnO nanorods. Rhodamine B degradation was used as a probe reaction to evaluate the effect of Co(2+) doping on ZnO nanorods and photocatalytic performance under UV light and visible light irradiation. Co(2+) ions acted as the trapping or recombination centers for electrons and holes, leading to a reduction in photodegradation efficiency under UV light illumination. Alternatively, Co(2+) ions enhanced the optical absorption and produced the photoinduced carriers under visible illumination in terms of two charge transfer transitions involving Co(2+) ions. Consequently, Co(2+) ions substituted in the lattice of ZnO nanorods significantly improved the visible light photocatalytic activity.     

Enhanced photocatalytic activity of ZnO/CuO nanocomposite for the degradation of textile dye on visible light illumination

The photocatalytic degradation of organic dyes such as methylene blue and methyl orange in the presence of various percentages of composite catalyst under visible light irradiation was carried out. The catalyst ZnO nanorods and ZnO/CuO nanocomposites of different weight ratios were prepared by new thermal decomposition method, which is simple and cost effective. The prepared catalysts were characterized by different techniques such as X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and UV–visible absorption spectroscopy. Further, the most photocatalytically active composite material was used for degradation of real textile waste water under visible light illumination. The irradiated samples were analysed by total organic carbon and chemical oxygen demand. The efficiency of the catalyst and their photocatalytic mechanism has been discussed in detail.     

A Simple Route to Reduced Graphene Oxide‐Draped Nanocomposites with Markedly Enhanced Visible‐Light Photocatalytic Performance

Nanocomposites (denoted RGO/ZnONRA) comprising reduced graphene oxide (RGO) draped over the surface of zinc oxide nanorod array (ZnONRA) were produced via a simple low‐temperature route, dispensing with the need for hydrothermal growth, electrochemical deposition or other complex treatments. The amount of deposited RGO can be readily tuned by controlling the concentration of graphene oxide (GO). Interestingly, the addition of Sn²⁺ not only enables the reduction of GO, but also functions as a bridge that connects the resulting RGO and ZnONRA. Remarkably, the incorporation of RGO improves the visible‐light absorption and reduces the bandgap of ZnO, thereby leading to the markedly improved visible‐light photocatalytic performance. Moreover, RGO/ZnONRA nanocomposites exhibit a superior stability as a result of the surface protection of ZnONRA by RGO. The mechanism on the improved photocatalytic performance based on the cophotosensitizations under the visible‐light irradiation has been proposed. This simple yet effective route to the RGO‐decorated semiconductor nanocomposites renders the better visible‐light utilization, which may offer great potential for use in photocatalytic degradation of organic pollutants, solar cells, and optoelectronic materials and devices.     

ZnO/CNTs复合材料的制备、表征及光催化性能

采用水热法制备了一系列氧化锌和碳纳米管的复合材料(ZnO/CNTs),详细考察了碳纳米管的含量对复合材料光催化性能的影响。利用X射线衍射仪、紫外-可见漫反射吸收光谱、扫描电子显微镜、X射线能谱、透射电子显微镜、X射线光电子能谱和氮气吸附-脱附等测试手段对样品的结构、形貌和光学性质进行了表征,并用亚甲基蓝溶液模拟污染物,评价了ZnO/CNTs复合材料的光催化性能。结果表明:添加CNTs提高了ZnO的比表面积,增强了ZnO的可见光吸收。ZnO/CNTs复合材料较纯ZnO具有更高的光催化活性,并且随着CNTs含量的增加,ZnO/CNTs复合材料的光催化活性呈先增加后减小的趋势。当CNTs的含量为0.3%(质量分数)时,ZnO/CNTs复合材料的光催化活性最高,经过50 min光照后,亚甲基蓝的降解率达到了96.2%。     

Enhanced visible light responsive photocatalysis by ZnO:Mg/RGO nanocomposites

Mg and RGO activated ZnO nanocomposites were prepared using a low-cost soft chemical method. As per the structural studies the samples exhibit wurtzite structure of ZnO with hexagonal crystal system. No secondary phases were observed. The photocatalytic activity of the prepared samples were assessed through the degradation of cationic dyes, methylene blue (MB) and malachite green (MG) under visible light irradiation. The studies revealed that the ZnO:Mg/RGO nanocomposite exhibits enhanced photocatalytic as well as antibacterial behavior compared to bare ZnO. The optical, structural and surface morphological studies support the reports on the photocatalytic and antibacterial activities of the synthesized samples.     

Effect of leavening agent on structural and photocatalytic properties of ZnO nanorods

In the present work, we have demonstrated a simple, facile, one-step, rapid and cost effective synthesis of ZnO nanorods through the thermal decomposition of zinc acetate and leavening agent (NaHCO₃). The silver nanoparticles (AgNPs) were deposited on the surface of ZnO nanorods by photocatalytic reduction of Ag (I) to Ag(0). As synthesized ZnO nanorods and Ag–ZnO nanocomposites were characterized by using X-ray Diffraction, field emission scanning electron microscope, high-resolution transmission electron microscope and diffuse reflectance spectroscopy. The photocatalytic activities of the ZnO nanorods and Ag–ZnO nanocomposites were evaluated for the photodegradation of Methyl Orange (MO) under UV and sunlight irradiation. The use of common leavening agent helps to prevent the aggregation of ZnO nanorods, further it hinders crystallite growth and narrowing the diameter of nanorods by the evolution of carbon dioxide during calcination. The ZnO nanorods and Ag–ZnO nanocomposite exhibited an enhanced photocatalytic activity and separation of photogenerated electron and hole pairs. Due to effect of leavening agent and AgNPs deposited on surface of ZnO nanorods finds best catalyst for the 99% degradation of MO within 30 min compared to ZnO.     

Fabrication of sandwich-structured ZnO/reduced graphite oxide composite and its photocatalytic properties

ZnO/RGO (ZnO/Reduced Graphite Oxide) composites with sandwich structure (layered structure) were synthesized at relatively low temperature (60 °C) using ZnSO₄ and GO (Graphite Oxide) as precursors. Compared with pure ZnO, ZnO/RGO composites showed greatly enhanced-UV photocatalytic activity for the degradation of the organic dye methyl orange (MO). The structure and morphology of as-prepared samples have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FE-SEM), etc. ZnO/RGO composites had a sandwich structure, which would be enhanced when exfoliated GO was used. During the formation the composites, GO was reduced to RGO (graphite-like carbon named as Reduced Graphite Oxide, RGO). The groups which exist in GO (such as C=O, C–O–C) disappeared or obviously weakened, while the groups similar to those in graphite (such as C=C) appeared at the same time. Photoluminescence (PL) spectra of ZnO/RGO showed a significant decline compared to that of pure ZnO, which suggests that the recombination of excited electron–hole pair (e⁻–h⁺) may be efficiently inhibited by the transfer of electrons to the carbon neighbor. The enhanced-photocatalytic activity for ZnO/RGO can be attributed to the migration effect of photoinduced electrons on the interface of RGO and ZnO. The photocorrosion effect of ZnO was found to be evidently suppressed according to Inductively Coupled Plasma Optical Emission Spectrometry (ICP).     

离子液体中纤维素/TiO_2复合材料的制备及其性能

以离子液体1-丁基-3-甲基咪唑氯盐BMIMCl为反应介质,钛酸丁酯作为钛前驱物,采用溶胶-凝胶法制备TiO_2,并将其负载在纤维素上,制备纤维素/TiO_2复合材料。采用单因素实验对反应条件进行优化,用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、紫外光漫反射(DRS)及热分析仪(TG)对复合材料结构及性能进行表征。以紫外光为光源,研究纤维素/TiO_2复合材料对甲基橙水溶液的光催化降解性能。结果表明:采用离子液体BMIMCl作为反应介质,可在常温常压下制备出高活性的光催化复合材料;TiO_2负载于纤维素后的复合材料对甲基橙的降解率在80min达到97.09%,与未负载的纳米TiO_2光催化剂相比,复合材料对甲基橙的降解率提高了37%。纤维素/TiO_2复合材料重复利用4次后对甲基橙的降解率仍能达到62.66%。     

A high performance cobalt-doped ZnO visible light photocatalyst and its photogenerated charge transfer properties

Highly photocatalytically active cobalt-doped ZnO (ZnO:Co) nanorods have been prepared by a facile hydrothermal process. X-ray diffraction, X-ray photoelectron spectroscopy, Raman scattering and UV-vis diffuse reflectance spectroscopy confirmed that the dopant ions substitute for some of the lattice zinc ions, and furthermore, that Co²⁺ and Co³⁺ ions coexist. The as-prepared ZnO:Co samples have an extended light absorption range compared with pure ZnO and showed highly efficient photocatalytic activity, only requiring 60 min to decompose ∼93% of alizarin red dye under visible light irradiation (λ > 420 nm). The photophysical mechanism of the visible photocatalytic activity was investigated with the help of surface photovoltage spectroscopy. The results indicated that a strong electronic interaction between the Co and ZnO was present, and that the incorporation of Co promoted the charge separation and enhanced the charge transfer ability and, at the same time, effectively inhibited the recombination of photogenerated charge carriers in ZnO, resulting in high visible light photocatalytic activity.      

Photodegradation pathway of rhodamine B with novel Au nanorods @ ZnO microspheres driven by visible light irradiation

A series of Au–ZnO photocatalysts were successfully synthesized from ZnO microspheres impregnated with Au nanorods by the seed-mediated method, and their photocatalytic activity of degradation of rhodamine B (RhB) was investigated. The nanocomposite catalyst exhibited high photocatalytic activity and degraded 92% of RhB solution under visible light irradiation in 330 min. The enhancement of photocatalytic effects was mainly ascribed to the surface plasmon resonance effect of Au nanorods; therefore, Au–ZnO spheres can absorb resonant photons and transfer the electron to the conduction band (CB) of ZnO leading to the separation of electrons and holes under visible light. Meanwhile, the photocatalytic performance was beneficial from the flower-like porous structure of ZnO, which enhances adsorption of the dye molecules and dissolved oxygen on the catalyst surface and facilitates the electron/hole transfer. Furthermore, the degradation pathway was proposed on the basis of the intermediates during the photodegradation process using liquid chromatography analysis coupled with mass spectroscopy (LC–MS). The degradation mechanism of pollutant is ascribed to the superoxide radicals (^·O^2?), which is the main oxidative species for the N-deethylated degradation of RhB. Moreover, the Au–ZnO photocatalysts demonstrated excellent photostability after five cycles. This work provides a facile and effective approach for removal of organic dyes under visible light and thus can be potentially used in the environmental purification.