Visible light active TiO2–ZnO composite films by cerium and fluorine codoping for photocatalytic decontamination

The visible light active Ce/F codoped TiO₂–ZnO composite films with a bad gap of 1.82 eV were successfully prepared though a simple sol–gel method. Experimental results indicated that the composite films showed excellent photocatalytic performance towards photocatalytic oxidation of organic pollutants including formaldehyde, acid naphthol red (ANR) and methyl green (MG). The catalysts were characterized by photoluminescence (PL) spectra, UV–vis diffraction reflectance absorption spectra (DRS), X-ray diffraction (XRD), differential thermal analysis-thermogravimetry (DTA-TG), field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), and N₂ adsorption/desorption isotherms. The DRS and PL spectra results showed that multi-modification not only induced strong visible light absorption but also reduced the recombination rate of electron–hole pairs. The DTA-TG and XRD results indicated that the crystal type of the TiO₂-based catalyst was mostly stabilized in anatase. The FE-SEM and BET surface area results revealed that the nanocrystalline Ce/F codoped TiO₂–ZnO composite samples with the larger specific surface area were composed of smaller nanoparticles compared to pure TiO₂. The mechanism of the enhanced photocatalytic activity was discussed in this study.     

Preparation and optical and photocatalytic properties of Ce-doped ZnO microstructures by simple solution method

We prepared ZnO photocatalysts with different Ce-doping levels using a simple one-step solution method utilizing Zn(NO₃)₂, Ce(NO₃)₃, and NaOH as raw materials. X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller surface area analysis, ultraviolet–visible diffusion spectroscopy, and photoluminescence spectroscopy were used to characterize the products. Ce-doping greatly influences the size, morphology, and optical properties of the samples. The particle size of Ce/ZnO samples decreases and the specific surface area increases accordingly compared with that of pure ZnO. The optical absorption edge of the Ce/ZnO samples displays an obvious red shift. Moreover, the band gap energy decreases with the increasing Ce content. The Ce/ZnO samples exhibit significantly enhanced photocatalytic performance than pure ZnO. The 1% Ce/ZnO sample possesses excellent photocatalytic activity in decomposing methylene blue (MB). The MB degradation efficiency reaches 96.11% after 140 min of irradiation.     

Fabrication of tin-doped zinc oxide by parallel flow co-precipitation with enhanced photocatalytic performance

Sn-doped ZnO photocatalysts with different molar ratios of Sn/Zn (1%, 2% and 3%) were prepared by a parallel flow precipitation. The photocatalysts fabricated were characterized by BET surface area, X-ray diffraction, scanning electron microscope, UV/Vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy, respectively. The results showed that doping ZnO with Sn increased BET surface area of ZnO. The XRD patterns of Sn-doped ZnO photocatalysts calcined at 573 K showed only the characteristic peaks of wurtzite-type. Doping ZnO with Sn changed the morphology of ZnO, the morphology changed from irregular lump and particle to irregular honeycomb. The photoinduced charge separation rate of 1% Sn doped-ZnO was higher than that of ZnO, while 2% and 3% Sn doped-ZnO had lower photovoltage than that of ZnO. The photocatalytic activity of Sn-doped ZnO photocatalysts for decolorization of methyl orange solution was evaluated, of all photocatalysts prepared, Sn-doped ZnO with 1% Sn exhibited the best photocatalytic activity and the underlying reason was discussed.     

垂直型MoS2/C60范德华异质结的研究

研究了采用垂直堆垛方式构筑的MoS2/C60范德华异质结的特性。利用直流磁控溅射法制备Mo薄膜,对Mo薄膜进行硫化退火处理得到MoS2薄膜,采用真空蒸镀法在MoS2薄膜上沉积C60进而形成MoS2/C60范德华异质结,并制备了Au/MoS2/C60/Al结构的器件。对MoS2薄膜的晶体结构进行了分析,对MoS2,C60及MoS2/C60薄膜的喇曼光谱及光吸收特性进行了测试和表征。结果表明:经过750℃退火后的MoS2晶型为2H型;由于在MoS2和C60薄膜之间范德华力的存在,相对于生长在Si/SiO2衬底上,沉积在MoS2上的C60薄膜喇曼特征峰发生红移;MoS2/C60薄膜在可见光范围内具有明显的光吸收特性;异质结表现出良好的整流特性,通过电子导电模型分析得出电子的传输机制包含热电子发射,空间电荷限制电流传导(SCLC)和隧穿现象。     

Improvement of visible light photocatalytic activity over graphene oxide/CuInS2/ZnO nanocomposite synthesized by hydrothermal method

In this study, graphene oxide/CuInS₂/ZnO as a new photocatalyst with light absorption properties in the visible region were successfully synthesized via hydrothermal route. The UV–vis absorption spectra of the catalyst suggested that the graphene oxide/CuInS₂/ZnO is active under visible light. It was evaluated the photocatalytic activities of graphene oxide/CuInS₂/ZnO on the degradation of Rhodamine B under visible light irradiation and was found that the graphene oxide/CuInS₂/ZnO obtained exhibit photocatalytic activity higher than single ZnO and CuInS₂/ZnO. Presence of graphene oxide with high specific surface area and great conductivity make it as a good support for CuInS₂/ZnO and improves removal efficiency for degradation of Rhodamine B.     

Solid state synthesis of erbium doped ZnO with excellent photocatalytic activity and enhanced visible light emission

The doped ZnO crystals with different erbium content were prepared by solid state reaction technique. The method is simple, relatively less expense and enables the production in large scale. The samples were characterised by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV/vis diffuse reflectance spectroscopy and photoluminescence techniques. Photocatalytic activity of samples was investigated by the degradation of methylene blue under UV light irradiation and was observed that, small fractions of erbium incorporation have a significant role in the enhancement of photocatalytic activity of ZnO. And the good stability of prepared catalysts makes them suitable for practical applications. Fluorescent property studies of erbium doped ZnO at room temperature show enhanced visible light emission due to the production of induced defects like antisite oxygen O_Zn and interstitial oxygen O_i. This work reports the co-existence of two mutually exclusive properties such as fluorescence and photocatalytic activity at their best in 0.6 wt% erbium doped ZnO.     

Photocatalytic and magnetic properties of Zn1−xCrxO nanocomposites prepared by a co-precipitation method

Polyvinyl pyrrolidone (PVP) capped Zn_1−xCr_xO (0.000001≤x≤0.1) nanocomposites were successfully synthesized using a simple chemical co-precipitation technique. The synthesized nanostructures were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), energy dispersive X-ray fluorescence (EDXRF), Fourier-transform infrared spectroscopy (FTIR), UV–visible spectroscopy, photoluminescence (PL) and vibrating sample magnetometer (VSM) measurements. The structural characterization by XRD, TEM, FTIR and EDXRF confirmed the formation of wurtzite structure and incorporation of Cr in the ZnO lattice. The photocatalytic activities of as prepared nanocomposites were evaluated by degradation of methylene blue (MB) dye in aqueous solution under UV/sunlight light irradiation. The results demonstrated that Zn_1−xCr_xO (x=0.0001) nanocomposite effectively bleached out MB, showing as impressive photocatalytic enhancement over pure ZnO and ZnS nanoparticles. This enhanced photocatalytic activity at optimum concentration was attributed to increased absorption ability of light and high separation rate of photoinduced charge carriers on the nanocomposite photocatalyst surface. The VSM measurements showed significant ferromagnetism in Cr-doped ZnO nanostructures and the value of saturated magnetism was found to decrease with increase in Cr content.     

Synthesis and characterization of cerium–silver co-doped zinc oxide as a novel sunlight-driven photocatalyst for effective degradation of Reactive Red 120 dye

Cerium–silver (Ce–Ag) co-doped ZnO was synthesized by precipitation–decomposition and tested for the degradation of Reactive Red 120 dye under natural sun light irradiation. Three weight percent Ce co-doped Ag–ZnO was found to be most efficient. Hence, this catalyst (3 wt% Ce–Ag–ZnO) has been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). XRD and XPS reveal the presence of metallic Ag and tetravalent Ce. Ag and Ce shift the absorption of ZnO to entire visible region. It was found that the Ce–Ag–ZnO exhibited higher degradation efficiency when compared to Ag-ZnO, Ce–ZnO, prepared ZnO, Commercial ZnO, TiO₂, and TiO₂-P25 at neutral pH (=7). Quantum yields of all processes were calculated and compared. Higher activity of Ce–Ag–ZnO in natural sunlight may be due to higher visible light absorption of Ce–Ag–ZnO when compared to native ZnO. The influences of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo mineralization of RR 120 have been analyzed. The mineralization of RR 120 dye was confirmed by chemical oxygen demand (COD) measurements. A dual mechanism has been proposed for efficient degradation of RR 120 dye by Ce–Ag–ZnO under solar light at neutral pH. This photocatalyst was found to be reusable up to four runs.     

Ag掺杂ZnO/GaN异质结可见光吸收特性的第一性原理

ZnO/GaN异质结带隙宽度较宽,制约了对可见光的吸收。为研究Ag对ZnO/GaN异质结可见光吸收的影响,在(1-100)非极性面上构建GaN/ZnO异质结,并用Ag分别取代不同位置的Zn和Ga原子,采用第一性原理计算Ag掺杂对ZnO/GaN异质结稳定性、电子结构、光学性质和带边位置的影响。研究结果表明：Ag掺杂ZnO/GaN异质结形成能为负值,结构稳定;Ag置换Zn和Ga使带隙宽度由2.93 eV分别减小至2.7 eV和2.3 eV,吸收系数和光电导产生红移,有利于可见光的吸收,Ag掺杂ZnO/GaN异质结具有良好的光催化活性。     

Preparation,characterization and photocatalytic properties of polythiophene-sensitized zinc oxide hybrid nanocomposites

The composites of polythiophene (PT)/zinc oxide (ZnO) nanoparticles with different PT wt%, (2%, 4%, 6%, 10% and 20%), were synthesized by an in situ chemical oxidative polymerization method. Zinc oxide nanoparticles, prepared by polymer pyrolysis method, with average particle size of 30 nm were used as inorganic phase of these composites. The particle size of ZnO powder was measured by transmission electron microscopy (TEM). FTIR measurements and X-ray diffraction analyses showed that PT/ZnO composites were successfully synthesized. Optical properties of the prepared composites were investigated by diffuse reflectance spectroscopy (DRS) that showed a broad peak in the visible region. The morphologies of the obtained composites were studied by scanning electron microscopy (SEM). Also Barrett–Emmett–Teller (BET) technique was used to measure the specific surface area of the samples. The photocatalytic activities of the composites were evaluated by degradation of methyl orange (MO) aqueous solution under visible light (9 W LED lamp) and sunlight irradiation.     

Preparation and characterization of perovskite-type Titania-bearing blast furnace slag photocatalyst

Perovskite-type titania-bearing blast furnace slag (TBBFS) photocatalysts were prepared by the high-energy ball milling method at different calcination temperatures. The particle size and ultraviolet light-absorption capacity of titania-bearing blast furnace slag powders increased with increase in the calcination temperature. Its photocatalytic activity was checked through the photocatalytic reduction of Cr(VI) as a model compound under ultraviolet–visible light irradiation. Titania-bearing blast furnace slag powders calcined at 700 °C showed a higher catalytic activity compared to other titania-bearing blast furnace slag catalysts, indicating that the increase in calcination temperature could improve their photocatalytic activities.     

Localized Surface Plasmon Resonance Enhanced Photocatalytic Hydrogen Evolution via Pt@Au NRs/C3N4 Nanotubes under Visible‐Light Irradiation

Au nanorods (NRs) decorated carbon nitride nanotubes (Au NRs/CNNTs) photocatalysts have been designed and prepared by impregnation–annealing approach. Localized surface plasmon resonance (LSPR) peaks of Au NRs can be adjusted by changing the aspect ratios, and the light absorption range of Au NRs/CNNTs is extended to longer wavelength even near‐infrared light. Optimal composition of Pt@Au NR₇₆₉/CNNT₆₅₀ has been achieved by adjusting the LSPR peaks of Au NRs and further depositing Pt nanoparticles (NPs), and the photocatalytic H₂ evolution rate is 207.0 µmol h^?1 (20 mg catalyst). Preliminary LSPR enhancement photocatalytic mechanism is suggested. On one hand, LSPR of Au NRs is beneficial for visible‐light utilization. On the other hand, Pt NPs and Au NRs have a synergetic enhancement effect on photocatalytic H₂ evolution of CNNTs, in which the local electromagnetic field can improve the photogenerated carrier separation and direct electron transfer increases the hot electron concentration while Au NRs as the electron channel can well restrain charge recombination, finally Pt as co‐catalyst can boost H⁺ reduction rate. This work provides a new way to develop efficient photocatalysts for splitting water, which can simultaneously extend light absorption range and facilitate carrier generation, transportation and reduce carrier recombination.     

铁、镧共掺杂纳米TiO2可见光催化性能研究

通过溶胶-凝胶(Sol-Gel)法制备了铁、镧共掺杂纳米TiO2,采用X线衍射仪(XRD)、X线光电子能谱(XPS)、紫外-可见分光光度计(UV-Vis)和荧光分光光度计(FL)等测试手段对样品进行表征。结果表明,500℃煅烧后的掺杂TiO2均呈锐钛矿型,平均粒径为6.1nm,掺杂抑制了TiO2粒径的长大,掺杂的Fe3+、La3+能有效进入TiO2晶格。掺杂使TiO2的吸收带边红移且在可见光区的光吸收增强,样品的荧光强度越小,催化效果越好。可见光光催化降解甲基橙实验结果表明,可见光照射5h,最佳共掺杂的0.01%Fe/0.6%La-TiO2对甲基橙的降解率达40.7%。     

Two novel Bi-based oxychloride photocatalysts: Synthesis,optical property and visible-light-responsive photocatalytic activity

Two novel visible-light-responsive bismuth oxychloride photocatalysts Bi₂EuO₄Cl and Bi₂NdO₄Cl have been successfully developed via a solid-state reaction route. Their crystal structures and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), diffuse reflectance spectra (DRS), and photoluminescence (PL) spectra. Fascinatingly, both the compounds possess considerable optical absorption in a broad region ranging from UV light to visible light. The indirect-transition optical band gaps of Bi₂EuO₄Cl and Bi₂NdO₄Cl are estimated to be 2.21 and 1.89 eV, respectively. For the first time, their photocatalytic activities were determined by photodecomposition of methylene blue (MB) in aqueous solution under visible light (λ>420 nm). The results revealed that both Bi₂EuO₄Cl and Bi₂NdO₄Cl can be used as effective visible-light-driven photocatalysts. In addition, theoretical calculations on the electronic structure, orbital constitutions and optical absorption of Bi₂NdO₄Cl were also performed. These findings shed light on the exploration of new photocatalytic materials activated by visible light.     

Palladium-decorated zinc sulfide/reduced graphene oxide nanocomposites for enhanced visible light-driven photodegradation of indigo carmine

The removal of toxic organic pollutants from wastewater using reduced graphene oxide (rGO) based photocatalysts has dominated recent scientific research. As a result numerous nanomaterials have been studied and used for wastewater remediation. ZnS has been widely studied due to its versatile application in photocatalysis. This study presents the synthesis of a series of Pd-decorated ZnS/rGO nanocomposites by a coprecipitation method. The materials were characterized using Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM)–EDS, UV/visible spectrophotometry, and BET surface area analysis. Indigo carmine (IC) dye (20 ppm) was chosen as a model for organic pollutants and was used to evaluate the photocatalytic performance of the Pd–ZnS/rGO nanocomposites under simulated solar light with varying concentrations of Pd in the host material. Pd–ZnS/rGO showed significant visible light induced photocatalytic activity towards the degradation of IC. Highest photocatalytic activity was observed for the 1.0% Pd–ZnS/rGO sample (k=2.19×10⁻² min⁻¹).     

Nano sized ZnO composites: Preparation,characterization and application as photocatalysts for degradation of AB92 azo dye

ZnO and Mordenite zeolite (MOR) nanoparticles were prepared by precipitation process using ultrasonic irradiation and hydrothermal method, respectively. Supported ZnO catalysts were prepared and the effect of different supports on the photocatalytic activity of ZnO nanoparticles was investigated. All prepared samples were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform-Infra Red Spectroscopy (FTIR), UV–vis spectroscopy (UV–vis) and BET surface area technique. The photocatalytic activity of the synthesized catalysts was elucidated using the photo-oxidation of Acid Blue 92 (AB92) as a hazardous pollutant under UV light. The effect of different parameters such as catalyst concentration, initial dye concentration, pH, UV irradiation and amount of ZnO loaded on the nanocomposites have been examined on the yield and the rate of photocatalytic degradation process. The photodegradation results of AB92 in aqueous medium under UV irradiation revealed that nanocomposite of ZnO and mordenite zeolite exhibit much higher photocatalytic activity than the other nanocomposites and pure ZnO. It was found that the type of support plays an important role in photocatalytic oxidation of AB92 and significantly improved the photocatalytic activity of ZnO. Chemical Oxygen Demand (COD) for dye solutions were examined at regular intervals and gave a good idea about mineralization of the dye.     

Preparation and photocatalytic performance of Ag/ZnO nano-composites

Ag/ZnO nano-composites sized between 20 and 50 nm were prepared by the coordination homogeneous co-precipitation method. Thermogravimetry/differential thermal analysis (TG-DTA), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet–visible (UV–vis) were used to characterize the microstructure and morphology of the precursor and the products obtained at various temperatures. The research on the growth dynamics of product Ag/ZnO showed that the dynamic growth index was 1.32, indicating that the rate of the grain growth was quick at 300–600 °C. The results of the photocatalytic degradation of methyl orange (MO) in aqueous solution indicated that the Ag/ZnO photocatalyst prepared by the coordination homogeneous co-precipitation method exhibited better photocatalytic performance than that prepared by the photoreduction method, especially the photocatalyst calcined at 300 °C, and the photocatalytic performance decreased when the calcining temperature increased from 300 to 700 °C.     

Development of novel Ag modified BiOF squares/g-C3N4 composite for photocatalytic applications

A novel Ag modified BiOF/g-C₃N₄ (Ag-BiOF/g-C₃N₄) organic–inorganic hybrid photocatalysts have been synthesized by a facile solvothermal route. The photocatalyst was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflection spectroscopy (UV-DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic studies reveals that the as-prepared Ag-BiOF/g-C₃N₄ photocatalyst exhibited significantly enhanced photocatalytic activity than the pure BiOF and BiOF/g-C₃N₄ photocatalysts toward degrading methylene blue (MB) under visible light irradiation. The heterostructured combination of Ag, g-C₃N₄ and BiOF micro squares provides synergistic photocatalytic performance through an efficient electron transport mechanism.     

Photocatalytic degradation of erythromycin under visible light by zinc phthalocyanine-modified titania nanoparticles

Zinc phthalocyanine modified TiO₂ nanoparticles (Znpc–TiO₂) were prepared by the chemical impregnation method to improve the photocatalytic activity of TiO₂ under visible light. The prepared nanoparticles were characterized by UV–vis diffuse reflectance spectroscopy (UV–vis-DRS), X-ray powder diffraction, scanning electron microscopy transmission electron microscopy and Brunauer-Emmett-Teller. surface area analysis techniques. The photocatalytic activity of Znpc–TiO₂ was investigated for the degradation of erythromycin. The results revealed that UV–vis absorption edge of Znpc–TiO₂ is slightly shifted towards visible region and it has a higher surface area than that of TiO₂. The photocatalytic activity of Znpc–TiO₂ was superior (74.21%) than that of TiO₂ (31.57%). Besides the photocatalyst (Znpc–TiO₂) is stable and may be reused for several times.     

Kelp-inspired N–I-doped ZnO photocatalysts with highly efficient catalytic activity

Efficient N–I-doped ZnO photocatalysts with hierarchical structures are fabricated with kelp as the template. Abundant nitrogen and iodine are successfully simultaneously introduced into the bulk ZnO crystals though calcination under high temperature (600 °C). The morphology, structure, composition, and optical absorption properties of the kelp-templated ZnO are characterized by X-ray diffraction (XRD), field-emission scanning microscopy (FESEM), transmission electron microscopy (TEM), and diffuse reflectance spectra (DRS), respectively. The band gap of the kelp-templated ZnO is narrowed by the N–I coping. The photocatalytic activity under UV-irradiation of the kelp-templated ZnO is about 23.1 times and 1.1 times that of common ZnO and P25, respectively. In addition, no obvious activity of the kelp-templated ZnO is decreased, during five cycle runs. The efficient photocatalytic activity of the kelp-templated ZnO is attributed to the sufficient UV-light utilization and efficient separation of electron–hole pairs.