Enhanced photocatalytic activity of bismuth molybdate via hybridization with carbon

The bismuth molybdate Bi_3.64Mo_0.36O_6.55 (BMO) was successfully synthesized by a rapid and convenient microwave-assisted method. Carbon was introduced to hybridize with BMO material (BMO/C) through the simple combination of hydrothermal process in the presence of glucose and subsequent calcination treatment in N₂ gas at 280 °C. The products were characterized by the study of X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that carbon did not affect the final crystalline structure of BMO, but it had great influences on the photocatalytic activity of BMO towards rhodamine-B (RhB) degradation. The improved photocatalytic performance could be ascribed to the enhanced photogenerated electron-hole separation and more RhB adsorption associated with carbon.     

Photoassisted fabrication of zinc indium oxide/oxysulfide composite for enhanced photocatalytic H2 evolution under visible-light irradiation

Abstract

A photoassisted approach has been developed to synthesize a zinc indium oxide (Zn₅In₂O₈)/oxysulfide composite through in situ sulfuration of vacancy-rich Zn₅In₂O₈. It was found that vacancies have a considerable impact on the formation of the composite. The composite exhibited an increased photocatalytic H₂ evolution activity under visible-light irradiation, which probably resulted from the enhanced ability to separate photoinduced electrons and holes. The H₂ evolution rate over the composite was about 17 times higher when using vacancy-rich rather than conventional Zn₅In₂O₈. This study provides a new method of improving the activity of photocatalysts.     

Photoassisted fabrication of zinc indium oxide/oxysulfide composite for enhanced photocatalytic H2 evolution under visible-light irradiation

A photoassisted approach has been developed to synthesize a zinc indium oxide (Zn₅In₂O₈)/oxysulfide composite through in situ sulfuration of vacancy-rich Zn₅In₂O₈. It was found that vacancies have a considerable impact on the formation of the composite. The composite exhibited an increased photocatalytic H₂ evolution activity under visible-light irradiation, which probably resulted from the enhanced ability to separate photoinduced electrons and holes. The H₂ evolution rate over the composite was about 17 times higher when using vacancy-rich rather than conventional Zn₅In₂O₈. This study provides a new method of improving the activity of photocatalysts.     

Fabrication and efficient photocatalytic degradation of methylene blue over CuO/BiVO4 composite under visible-light irradiation

CuO/BiVO₄ composite photocatalysts were prepared by solution combustion synthesis method and impregnation technique. X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scan electron microscopy and UV-vis diffusion reflectance spectra were used to identify the physical properties and photophysical properties of CuO/BiVO₄ composite photocatalysts. The photocatalysts exhibit the enhanced photocatalytic properties for degradation of methylene blue under visible-light (λ > 420 nm). The mechanism of improved photocatalytic activity is also discussed.     

Photocatalytic degradation of rhodamine B by Bi2O3/Cs3PW12O40 composite under visible-light irradiation and its enhanced photocatalytic activity

Journal of Materials Science: Materials in Electronics - A novel Bi2O3/Cs3PW12O40 (Bi2O3/CsPW) composite was prepared by depositing Bi2O3 on the surface of spherical Cs3PW12O40. The synthesized...     

Preparation of nitrogen co-doped SiO2/TiO2 thin films on ceramic with enhanced photocatalytic activity under visible-light irradiation

In this study, we have successfully deposited N-doped SiO₂/TiO₂ thin films on ceramic tile substrates by sol–gel method for auto cleaning purpose. After dip coating and annealing process the film was transparent, smooth and had a strong adhesion on the ceramic tile surface. The synthesised catalysts were then characterised by using several analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM) and UV-vis absorption spectroscopy (UV-vis). The analytical results revealed that the optical response of the synthesised N-doped SiO₂/TiO₂ thin films was shifted from the ultraviolet to the visible light region. The nitrogen substituted some of the lattice oxygen atoms. The surface area of co-doped catalyst increased, and its photocatalytic efficiency was enhanced. The photocatalytic tests indicated that nitrogen co-doped SiO₂/TiO₂ thin films demonstrated higher than of the SiO₂/TiO₂ activity in decolouring of methylene blue under visible light. The enhanced photocatalytic activity was attributed to an increasing of the surface area and a forming of more hydroxyl groups in the doped catalyst.     

Synthesis and photocatalytic activity of nanocrystalline TiO2-SrO composite powders under visible light irradiation

Nano-sized homogeneously distributed TiO₂-20, -40, -60 wt.% SrO composite powders were successfully synthesized by a sol-gel method. The as-received amorphous TiO₂—20 wt.% SrO composite powders were crystallized with anatase TiO₂ at around 750 °C. As calcination temperatures increased, the anatase TiO₂ crystalline phase was transformed to rutile TiO₂ at about 900 °C, whereas nano-sized, squarish SrTiO₃ phase was detected. The peaks obtained after calcining at 1050 °C mainly exhibited the rutile TiO₂ and SrTiO₃ phases. However, a small number of SrO₂ peaks were also detected. For the comparison of photocatalytic activity depending on light sources, TiO₂-SrO composite powders were tested in phenol degradation. TiO₂-60 wt.% SrO composite powder showed good visible light photoactivity for the photo-oxidation of phenol.     

Excellent photocatalytic performance under visible-light irradiation of ZnS/rGO nanocomposites synthesized by a green method

ZnS/graphene nanocomposites with different graphene concentrations (5, 10 and 15 wt.%) were synthesized using L-cysteine as surfactant and graphene oxide (GO) powders as graphene source. Excellent performance for nanocomposites to remove methylene blue (MB) dye and hexavalent chromium (Cr(VI)) under visible-light illumination was revealed. TEM images showed that ZnS NPs were decorated on GO sheets and the GO caused a significant decrease in the ZnS diameter size. XRD patterns, XPS and FTIR spectroscopy results indicated that GO sheets changed into reduced graphene oxide (rGO) during the synthesis process. Photocurrent measurements under a visiblelight source indicated a good chemical reaction between ZnS NPs and rGO sheets.     

Preparation and characterization of N–I co-doped nanocrystal anatase TiO2 with enhanced photocatalytic activity under visible-light irradiation

N–I co-doped TiO₂ nanoparticles were prepared by hydrolysis method, using ammonia and iodic acid as the doping sources and Ti(OBu)₄ as the titanium source. The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible diffuse reflection spectroscopy (UV–vis DRS). XRD spectra show that N–I–TiO₂ samples calcined at 673 K for 3 h are of anatase structure. XPS analysis of N–I–TiO₂samples indicates that some N atoms replace O atoms in TiO₂ lattice, and I exist in I⁷⁺, I⁻ and I⁵⁺ chemical states in the samples. UV–vis DRS results reveal that N–I–TiO₂ had significant optical absorption in the region of 400–600 nm. The photocatalytic activity of catalysts was evaluated by monitoring the photocatalytic degradation of methyl orange (MO). Compared with P25 and mono-doped TiO₂, N–I–TiO₂ powder shows higher photocatalytic activity under both visible-light (λ > 420 nm) and UV–vis light irradiation. Furthermore, N–I–TiO₂ also displays higher COD removal rate under UV–vis light irradiation.     

氮掺杂TiO_2中空复合微球的制备及可见光光催化性能

为了提高TiO2的可见光光催化性能,以微米级聚苯乙烯微球为模板,钛酸四丁酯为前驱体,三乙胺为氮源,采用静电吸附自组装法制备了粒径为1.20μm、壳层的厚度约为30nm且球形形貌良好的氮掺杂TiO2中空复合微球,采用SEM、XPS、XRD和紫外-可见分光光度计研究了其结构及光催化性能。结果表明:氮进入TiO2晶格内取代了部分O并改变了晶格中Ti和O的化学状态,但对TiO2晶型结构没有明显影响;氮掺杂后的TiO2中空复合微球禁带宽度变窄,氮掺杂TiO2中空复合微球不仅在紫外区有较强的光吸收能力,在可见光区也表现出较强的光响应性,对甲基橙的光催化降解率较Degussa P25型纳米TiO2的明显增强。研究结果对TiO2在光催化领域的应用具有理论指导意义。     

具有可见光活性的TiO2薄膜的制备及光催化性能

运用磁控溅射技术在浸渍－提拉法制得的TiO2薄膜上溅射三氧化钨层得到光催化薄膜。采用SEM、XRD、AES、UV－vis漫反射光谱等方法表征催化剂薄膜的厚度、晶相结构、化学元素组成及光吸收性能。以甲基橙的光催化降解为反应模型，高压汞灯为光源，溅射有三氧化钨薄膜的光催化活性低于纯TiO2薄膜；滤过紫外光后，溅射有三化钨的薄膜光催化活性明显高于纯TiO2薄膜。本实验提供了一种制备高可见光活性的TiO2薄膜的方法。     

Improved visible-light responsive photocatalytic activity of N and Si co-doped titanias

Thermal reaction of titanium tetraisopropoxide and tetraethyl orthosilicate in 1,4-butanediol afforded nanocrystalline silica-modified titanias having large surface area and superior thermal stability. In this study, the thus-obtained silica-modified titanias were treated in an NH₃ flow at high temperatures, and their physical and photocatalytic properties were investigated. Compared with NH₃-treated TiO₂ without silica modification, the NH₃-treated silica-modified titanias showed a stronger absorption in the visible region (400–500 nm) and had a larger peak at 396 eV in the N 1s XPS spectrum. These results indicate that a larger amount of nitrogen was stably doped in the silica-modified titania. The obtained products exhibited a high photocatalytic activity for degradation of Rhodamine B and decomposition of acetaldehyde under visible light irradiation. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

氮掺杂钛精矿的制备及其可见光催化活性

以硝酸作为氮源,钛精矿为原料,采用超声波复合高能球磨法,在不同煅烧温度下合成了硝酸掺杂的钛精矿催化剂(nitric acid-modified titanium ore,NATO)。用X射线衍射(XRD)、傅立叶红外(FT-IR)、紫外-可见漫反射光谱(UV-Vis)、差热-热重(TG-DTA)和光致发光谱(PL)分析对NATO催化剂的结构和性能进行分析和表征,确定其由钛磁铁矿、钛铁矿、TiO2、钛铁氧化物等多种物相组成;在紫外-可见光区域都具有很强的光吸收能力。不同煅烧温度下,NATO催化剂的光催化活性由甲基橙的脱色率来评价,结果表明,煅烧温度为400℃时,NATO催化剂由于表面存在较高的硝酸盐含量和较高的可见光吸收能力及合适的晶相比,而具有较高的光催化活性,500W金卤灯照射1h,可将浓度为10mg/L的甲基橙废水完全降解。     

Enhanced photocatalytic performance of Fe-doped SnO2 nanoarchitectures under UV irradiation: synthesis and activity

A facile, sol–gel method has afforded highly crystalline, Fe-doped SnO₂ nanoarchitectures with efficient photocatalytic degradation of rhodamine B (RhB) under ultraviolet irradiation. The effects of iron modification to tin dioxide were investigated. The structural properties were characterized by powder X-ray diffraction, gas sorption (adsorption/desorption) techniques, scanning electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). The photocatalytic activity of these materials was studied by examining the degradation of RhB with pure SnO₂ and each Fe modified sample (3 and 5 %), all annealed at 350 °C. Diffraction results reveal that the synthesized nanocrystals are ~3 nm in diameter. Gas sorption analyses detail high-specific surface areas (>330 m² g^?1). Electron microscopy studies illustrate the enhanced porosity brought on through annealing. EDS confirms the presence of Fe in the most active Fe-modified SnO₂ sample. It is found that the 5 % Fe-modified SnO₂ degrades RhB by more than half after 2 h.     

Regulation on polymerization degree and surface feature in graphitic carbon nitride towards efficient photocatalytic H2 evolution under visible-light irradiation

A kind of graphitic carbon nitride(TSC-550)with high polymerization degree and improved surface property was prepared by a new precursor of thiosemicarbazide.Th...     

Nanoparticulate SnS as an efficient photocatalyst under visible-light irradiation

SnS nanoparticles were synthesized using cheap and less toxic SnCl₂·2H₂O as the tin (II) precursor. The prepared nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-Vis diffuse reflectance spectra (DRS). XRD and TEM results indicate that the prepared product is SnS nanosphere and has a grain size of 5 nm in diameter. DRS show that SnS possesses the absorption profile across the whole visible-light region. Furthermore, SnS has a high photocatalytic activity for the decomposition of Rhodamine B under visible-light. It is proposed that both the strong visible-light absorption and the multiple exciton excitation contribute to the high visible-light photocatalytic activity.     

磁性MCM-41/CdS的制备及其可见光催化性能研究

采用两步沉淀法将CdS沉积在磁性MCM-41上,制备新型磁性MCM-41/CdS复合材料。通过X射线衍射光谱(XRD)、高分辨透射电镜(HRTEM)、紫外-可见吸收光谱(UV-Vis)、振动样品磁强计(VSM)等对其进行表征。以亚甲基蓝(methylene blue,简称MB)为模拟污染物,考察了磁性MCM-41/CdS复合材料的可见光催化性能。结果表明,CdS能有效地沉积在磁性MCM-41上,与CdS相比,该复合材料对MB的光催化降解效率明显提高,且可通过外加磁场进行分离。     

Thermostable nitrogen-doped HTiNbO5 nanosheets with a high visible-light photocatalytic activity

Nitrogen-doped HTiNbO₅ nanosheets have been successfully synthesized by first exfoliating layered HTiNbO₅ in tetrabutylammonium hydroxide (TBAOH) to obtain HTiNbO₅ nanosheets and then heating the nanosheets with urea. The resulting samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and N₂ adsorption-desorption measurements. It was found that N-doping resulted in a much higher thermostability of the layered structure, intrinsic bandgap narrowing and a visible light response. The doped nitrogen atoms were mainly located in the interstitial sites of TiNbO₅ ⁻ lamellae and chemically bound to hydrogen ions. Compared with N-doped HTiNbO₅, N-doped HTiNbO₅ nanosheets had a much larger specific surface area and richer mesoporosity due to the rather loose and irregular arrangement of titanoniobate nanosheets. Both N-doped layered HTiNbO₅ and HTiNbO₅ nanosheets showed a very high visible-light photocatalytic activity for the degradation of rhodamine B (RhB) aqueous solution. Moreover, due to the considerably larger surface area, richer mesoporosity and stronger acidity, N-doped HTiNbO₅ nanosheets had an even higher activity than N-doped HTiNbO₅, although the latter had a stronger absorption in the visible region. The dye molecules were mainly degraded to aliphatic organic compounds and partially mineralized to CO₂ and/or CO, rather than being simply decolorized. The effect of photosensitization was insignificant and RhB was degraded mainly via the typical photocatalytic reaction routes. Two different reaction routes for the photodegradation of RhB under visible light irradiation over N-doped HTiNbO₅ nanosheets have been proposed. The present method can be extended to a large number of layered metal oxides that have the characteristics of intercalation and exfoliation, thus providing new opportunities for the fabrication of highly effective and potentially practical visible-light photocatalysts.      

Facile preparation of Ce-doped TiO2/diatomite granular composite with enhanced photocatalytic activity

Granule-shaped Ce-doped TiO₂/diatomite (GCTD) hybrid was prepared via sol-gel method. The physicochemical properties of this hybrid were characterized by various analytical methods. As carrier, diatomite was conducive to the dispersion of TiO₂ nanoparticles, hindering their agglomeration process. Compared to TiO₂, GCTD showed visible-light-driven photoactivity, which was evaluated by the degradation of oxytetracycline (OTC) and disinfection of three bacteria (Escherichia coli, Staphylococcus aureus and Klebsiella pneumonia) under visible light. The porous diatomite enhanced the photoactivity of TiO₂ via the adsorption towards target pollutants. The reusability experiment was conducted for 5 times, and the results showed that GCTD exhibited good photo-stability and reusability.