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.     

Photocatalytic degradation of pendimethalin over Cu2O/SnO2/graphene and SnO2/graphene nanocomposite photocatalysts under visible light irradiation

The Cu₂O/SnO₂/graphene (CSG) and SnO₂/graphene (SG) nanocomposite photocatalysts were prepared by simple sol-gel growth method, and characterized by Fourier transform infrared spectra (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) measurements, respectively. The photocatalytic efficiency of catalysts were evaluated by degradation of pendimethalin under visible light irradiation (λ > 420 nm), which conformed that CSG and SG exhibited better photocatalytic activity than SnO₂ or graphene alone. An effort has been made to correlate the photoelectro-chemical behavior of these samples to the rate of photocatalytic degradation of pendimethalin.     

A facile one step synthesis of SnO<Subscript>2</Subscript>/CuO and CuO/SnO<Subscript>2</Subscript> nanocomposites: photocatalytic application

Here novel photocatalysts, SnO₂/CuO and CuO/SnO₂ nanocomposites were successfully synthesized by chemical method at room temperature. X-ray Diffraction (XRD), transmission electron microscopy (TEM), Fourier transform Infrared (FT-IR), UV–Visible (UV–Vis) and photoluminescence (PL) spectroscopy were utilized for characterization of the nanocomposites. The photocatalytic activity of the nanocomposites was investigated. The hybrid nanocomposites exhibited high photocatalytic activity as evident from the degradation of methylene blue (MB) dye. The result revealed substantial degradation of the MB dye (92 and 69.5% degradation of SnO₂/CuO and CuO/SnO₂, respectively) under visible light illumination with short period of 30 min. Their large conduction band potential difference and the inner electrostatic field formed in the p–n heterojunction provide a strong driving force for the photogenerated electrons to move from Cu₂O to SnO₂ under visible light illumination. The excellent photodegradation of methylene blue suggested that the heterostructured SnO₂/CuO nanocomposite possessed higher charge separation and photodegradation abilities than CuO/SnO₂ nanocomposite under visible light irradiation.     

Controllable synthesis of SnO2 photocatalyst with superior photocatalytic activity for the degradation of methylene blue dye solution

SnO₂ photocatalyst was successfully synthesised by novel chemical route in hydrothermal environment and annealed at two different temperatures viz 550 and 600 °C, respectively. The crystal structure, optical properties, surface and bulk morphology have been characterised using various tools like X-ray diffraction (XRD), UV visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscope (TEM) and scanning electron microscope (SEM). Cubic, spheres and porous like morphology of SnO₂ photocatalyst was successfully confirmed using SEM micrographs and TEM. In addition to this the photocatalytic activity was evaluated towards the degradation of methylene blue dye solution. SnO₂ photocatalyst annealed at 600 °C exhibits excellent photocatalytic efficiency which may be attributed to the unique morphology, high crystalline nature and charge separation. The photocatalyst efficiency was further tested towards the concentration of dye, catalyst dosage and pH of the dye. The involvement of ?OH in the photocatalytic reaction was evidenced using trapping experiment by employing different scavengers. The photocatalyst was moderately active, stable upto its fifth usage and stability of the photocatalyst before and after the photocatalytic reaction was also been studied using XRD and SEM.     

Novel method for doping nano TiO2 photocatalysts by chemical vapour deposition

Highly active photocatalytic Fe-doped nano TiO₂ was successfully synthesised by chemical vapour deposition (CVD) method using FeCl₃ as Fe source. CVD was carried out by evaporating FeCl₃ at 350°C in nitrogen flow during 30–90?min. The amount of Fe incorporated into TiO₂ framework is adjusted by the amount of FeCl₃ used and the evaporation time. The obtained sample was characterised by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), energy dispersive X-ray spectroscopy (EDS), UV-Vis, Fourier transform-infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activities of the samples were tested in photocatalytic decomposition of 2-propanol in liquid phase using visible light instead of UV light irradiation. Non-doped TiO₂ and high Fe loading TiO₂ samples showed very low photocatalytic activity, whereas the low Fe loading TiO₂ sample exhibited high photocatalytic activity under visible light. The high photocatalytic activity of this sample was rationalised by the existence of defects (Ti–OH groups) as the active sites.     

Hydrothermal synthesis of hierarchical flower-like α-CNTs/SnO2 architectures with enhanced photocatalytic activity

The hierarchical flower-like α-CNTs/SnO₂ architectures composed of curved sheets are synthesized with hydrothermal method at 160?°C for 8?h. The α-CNTs/SnO₂ composite was doped with α-CNTs during preparation, the photocatalytic activity of α-CNTs/SnO₂ was evaluated by photodegradation of Rhodamine B (RhB) under simulated visible light. The results showed that the photocatalytic activity of α-CNTs/SnO₂ for degradation of RhB was up to 90.35% within 120?min, which was much higher than that of pure compound. It was significantly found that the introduction of α-CNTs, which may suppressed the recombination of photogenerated electron-hole pairs on the interface of SnO₂, leading to enhanced photocatalytic activity.     

Synthesis,characterization and photocatalytic activity of ZnO-SnO2 nanocomposites

Nanocomposites of coupled ZnO-SnO₂ photocatalysts were synthesized by the coprecipitation method and were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, surface area analyzer and scanning electron microscopy. Their photocatalytic activity was investigated under UV, visible and solar light and evaluated using methylene blue (MB) as a model pollutant. The performance of the coupled ZnO-SnO₂ photocatalysts was found to be related to the Zn/Sn molar ratio and to the calcination conditions. The photocatalyst with a Zn/Sn molar ratio of 1:0.05 calcined at 600 °C for 2 h showed the maximum degradation rate of MB under different lights used. Its photocatalytic activity was found to be about two times that of ZnO and about 10 times that of SnO₂ which can be explained by the heterojunction effect. Charge separation mechanism has been studied.     

Growth of Cu2O nanoparticle on reduced graphene sheets with high photocatalytic activity for degradation of Rhodamine B

Cu₂O–reduced graphene oxide (RGO) nanocomposite was synthesized by a simple one-pot solvothermal method. The morphology and properties of Cu₂O/RGO nanocomposites were characterized by scanning electron microscope, Raman spectroscopy, X-ray diffraction, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activities of the as-prepared nanocomposites were investigated by photodegrading Rhodamine B under visible light. Results show that Cu₂O/RGO nanocomposites exhibited a remarkably enhanced photocatalytic efficiency compared with pure Cu₂O nanoparticles and commercial P25. Moreover, we found that the content of graphene oxide introduced into composite material was a crucial factor for its improved photocatalytic performance.     

SnO<Subscript>2</Subscript>-based thin films with excellent photocatalytic performance

SnO₂ semiconductor is a new-typed promising photocatalyst, but wide application of SnO₂-based photocatalytic technology has been restricted by low visible light utilization efficiency and rapid recombination of photogenerated electrons–holes. To overcome these drawbacks, we prepared B/Fe codoped SnO₂–ZnO thin films on glass substrates through a simple sol–gel method. The photocatalytic activities of the films were evaluated by degradation of organic pollutants including acid naphthol red (ANR) and formaldehyde. UV–Vis absorption spectroscopy and photoluminescence (PL) spectra results revealed that the B/Fe codoped SnO₂–ZnO film not only enhanced optical absorption properties but also improved lifetime of the charge carriers. X-ray diffraction (XRD) results indicated that the nanocrystalline SnO₂ was a single crystal type of rutile. Field emission scanning electron microscopy (FE-SEM) results showed that the B/Fe codoped SnO2–ZnO film without cracks was composed of smaller nanoparticles or aggregates compared to pure SnO2 film. Brunauer–Emmett–Teller (BET) surface area results showed that the specific surface area of the B/Fe codoped SnO₂–ZnO was 85.2 m² g^?1, while that of the pure SnO₂ was 20.7 m² g^?1. Experimental results exhibited that the B/Fe codoped SnO₂–ZnO film had the best photocatalytic activity compared to a pure SnO₂ or singly-modified SnO₂ film.     

Synthesis of graphene oxide/Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript> composite with enhanced visible-light photocatalytic activity

The nano-scale Ag₃PO₄ was successfully synthesized by the silver ammonia complexing precipitation method at room temperature. And the Graphene oxide (GO)/Ag₃PO₄ nanocomposites with different contents of GO were successfully synthesized using the electrostatic driving method. The as-prepared GO/Ag₃PO₄ nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), confirming that Ag₃PO₄ were highly dispersed to GO sheet. The photocatalytic properties of GO/Ag₃PO₄ were evaluated by the degradation of Methyl Orange (MO) under visible light irradiation and solar irradiation respectively. The results showed that the photocatalytic efficiencies of GO/Ag₃PO₄ nanocomposites had enhanced largely and the kinetics reaction models were followed first-order. Furthermore, 5% GO/Ag₃PO₄ exhibited the highest photocatalytic activity on degradation of MO under visible-light irradiation. The improved photocatalytic performances of the GO/Ag₃PO₄ nanocomposites mainly attributed to the introducing of GO, which benefit for electron transfer and inhibit the recombination of electron–hole pairs, promoting the practical application of Ag₃PO₄ in water purification.     

Synthesis and photocatalytic performance of TiO<Subscript>2</Subscript> nanospheres–graphene nanocomposite under visible and UV light irradiation

In this article, we present a fast and simple method to produce TiO₂ nanospheres–graphene nanocomposite with high photocatalytic activity under visible and UV light irradiation. TiO₂ nanospheres were adsorbed on graphene in sol–gel process. First, titanium (IV) butoxide underwent hydrolysis in graphene oxide (GO) ethanol solution resulting in TiO₂ nanospheres deposition on GO. Next, the material was calcinated to generate the phase transition of TiO₂ into anatase and reduce GO to graphene. The detailed characterization of the material was performed via transmission electron microscopy, energy dispersive X-rays spectrometer, Fourier-transformed infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. Interestingly, the band-gap energy of the prepared photocatalyst was drastically decreased in comparison with the commercial photocatalyst P25 from 3.05 to 2.36 eV. This influenced in the activation of the material under visible light and resulted in high photocatalytic activity in the process of phenol decomposition in visible and UV irradiation.     

Synthesis and investigation of SnS<Subscript>2</Subscript>/RGO nanocomposites with different GO concentrations: structure and optical properties,photocatalytic performance

In this study, we report the synthesis of tin disulfide/reduced graphrene oxide (SnS₂/RGO) nanocomposites by a simple one-step hydrothermal method. In order to investigate the effect of RGO on the structure and optical properties and photocatalytic activity of the products a series of nanocomposites was prepared with different concentrations of GO. The samples were examined using X-ray diffraction, field emission scanning electron microscopy (FESEM), Raman spectroscopy, UV–Vis spectroscopy and photoluminescence techniques. The results confirmed the growth of SnS₂ with the hexagonal phase. FESEM analysis showed that the hexagonal tin disulfide nanoplates are uniformly dispersed on the surface of the graphene oxide sheets. The optical examination of SnS₂ and SnS₂/RGO nanocomposites indicated that the band gaps of all nanocomposites are greater than that of SnS₂ due to the quantum confinement effect. The photocatalytic activity of the SnS₂/RGO nanocomposites was investigated for degradation of the acid orange 7 dye under visible light. It was observed that all nanocomposites have a higher photocatalytic activity for the degradation in comparison with pure SnS₂. The optimum concentration of GO in SnS₂/RGO nanocomposite for achieving the highest photocatalytic efficiency (81%) was determined as 2 mg ml^?1 during 180 min.     

A facile route to synthesize ternary Cu2O quantum dot/graphene-TiO2 nanocomposites with an improved photocatalytic effect

A Cu₂O quantum dot/graphene-TiO₂ composite, a novel material, was successfully synthesized using a facile hydrothermal method. The hydrothermal reaction was used to load the Cu₂O and TiO₂ particles onto graphene sheets, and the resulting photocatalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy, and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (DRS). UV spectrophotometry was employed to measure the decrease in the concentration of rhodamine B (RhB), methylene blue trihydrate (MB), and reactive black B (RBB) dyes in an aqueous solution after degradation with the photocatalysts under irradiation with visible light. The results indicate that the quantum dot-sized Cu₂O is a promising material that contributes to the photocatalytic activity of Cu₂O quantum dot/graphene-TiO₂ composites.     

Oxygen vacancies facilitated photocatalytic detoxification of three typical contaminants over graphene oxide surface embellished BiOCl photocatalysts

A conventional solvothermal way was used to synthesize graphene oxide (GO)/BiOCl photocatalytic nanomaterials with enhanced photocatalytic performance. Due to the introduction of GO, there are intuitive changes in morphology, indicating that GO can guide the growth of GO/BiOCl catalysts. The results of X-ray photoelectron spectroscopy (XPS) and Raman show that a strong chemical interaction occurs around GO and BiOCl. The results of trapping experiments show that O₂^– is the major active species. XPS analysis confirms that the 0.75% GO/BiOCl produces the highest level of oxygen vacancies (OVs). All the GO/BiOCl photocatalysts possess better photocatalytic properties than the neat BiOCl, and 0.5% GO/BiOCl exhibits the highest photoactivity. The photocatalytic activity of 0.5% GO/BiOCl composite for detoxification of rhodamine B (RhB) and tetracycline (TC) under visible light illumination is 4.6 and 6.3 times of that on the reference BiOCl, separately, the photocatalytic activity of 0.5% GO/BiOCl for detoxication of perfluorooctanoic acid (PFOA) is 1.25 times of that of the single BiOCl under UV light illumination, which can be credited to the high separation rate of carriers and the strong interaction between GO and BiOCl. Combining with the results, a separation and transfer mechanism of carriers was revealed.     

An efficient visible light photocatalyst prepared from TiO<Subscript>2</Subscript> and polyvinyl chloride

An efficient visible light photocatalyst has been prepared from TiO₂ nanoparticles and a partly conjugated polymer derived from polyvinyl chloride (PVC). It was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The visible light photocatalytic activity of the as-prepared photocatalyst was evaluated by the photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation. The XPS, FT-IR, and Raman spectra show that the partly conjugated polymer derived from PVC exists on the surface of the TiO₂ nanoparticles. The UV–Vis DRS, XRD, and TEM results reveal that the modification of the partly conjugated polymer can obviously improve the absorbance of the TiO₂ nanoparticles in the range of visible light and hardly affect their size and crystallinity. The visible light photocatalytic activity of the as-prepared TiO₂ nanocomposites is higher than that of commercial TiO₂ (Degussa P25) and comparable with those of visible light photocatalysts reported in the literature. Their visible light photocatalytic stability is also good. The reasons for their excellent visible light photocatalytic activity and the major factors affecting their photocatalytic activity are discussed.     

Band gap narrowing and photocatalytic studies of Nd<Superscript>3+</Superscript> ion-doped SnO<Subscript>2</Subscript> nanoparticles using solar energy

Pure and Nd³⁺-doped tin oxide (SnO₂) nanoparticles have been prepared by the sol–gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive spectroscopy and UV–visible spectroscopy. The XRD patterns of all the samples are identified as tetragonal rutile-type SnO₂ phase which is further confirmed by TEM analysis. Neodymium doping introduces band gap narrowing in the prepared samples and enhances their absorption towards the visible-light region. The photocatalytic activity of all the samples was evaluated by monitoring the degradation of methylene blue solution under day light illumination and it was found that the photocatalytic activity significantly increases for the samples calcined at 600 than 400°C, which is due to the effective charge separation of photogenerated electron–hole pairs. The efficiency of photocatalysts was found to be related to neodymium doping percentage and calcination temperature.     

水热合成的MoS2/石墨烯/N-TiO2复合材料的可见光催化性能

以氧化石墨烯(GO)、钼酸、硫脲和TiN为原料,成功制备了MoS_2/石墨烯/N-TiO_2(MGNT)复合材料。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HR-TEM)、X射线光电子能谱(XPS)及紫外-可见漫反射光谱(UV-Vis DRS)等手段测试分析了样品的物相组成、形貌、成分和光吸收性能。紫外-可见漫反射测试结果表明,MoS_2、石墨烯共同修饰及氮掺杂使得TiO_2的吸收带边发生红移,且其可见光吸收性能明显提高。可见光照射下降解亚甲基蓝溶液的实验结果表明,MoS_2/石墨烯共同修饰的氮掺杂TiO_2的光催化降解性能分别是氮掺杂TiO_2(NT)和石墨烯修饰氮掺杂TiO_2(GNT)的1.82倍和1.59倍,其吸附性分别为氮掺杂TiO_2、石墨烯修饰氮掺杂TiO_2的11.14倍和4.77倍。     

Microwave Synthesis of Cu/Cu<Subscript>2</Subscript>O/SnO<Subscript>2</Subscript> Composite with Improved Photocatalytic Ability Using SnCl<Subscript>4</Subscript> as a Protector

Cu/Cu₂O/SnO₂ composites were successfully prepared with a facile microwave synthesis method. The structure of Cu/Cu₂O/SnO₂ composite was studied by morphology characterizations, such as X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy, which showed that the size of the Cu/Cu₂O/SnO₂ particles is 20–50 nm. The synthesis mechanism revealed that SnCl₄ obstructed between Cu(OH) and ethylene glycol, preventing Cu(OH) being reduced into Cu at high temperature. The photocatalytic property of Cu/Cu₂O/SnO₂ composite was investigated by degrading the mixed dyestuff under the irradiation of visible light at room temperature. Benefiting from the effect of electron transfer, the photocatalytic performance of the microwave-prepared Cu/Cu₂O/SnO₂ composite was much better than that of pure Cu₂O. The possible photocatalytic mechanism of the Cu/Cu₂O/SnO₂ composite catalysts was proposed and elaborated in this study. This synthesis of Cu/Cu₂O/SnO₂ composite may provide a method for other Cu₂O/semiconductor composites microwave preparation.     

Fabrication and photocatalytic property of ZnO nanorod arrays on Cu2O thin film

ZnO nanorod arrays were fabricated on Cu₂O thin film by a simple low-temperature liquid-phase-deposition method. The samples were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM). The UV-Vis spectroscopy showed that the obtained sample was able to absorb a large part of visible light (up to 650 nm). Their photocatalytic activities were investigated by degradation of dye methylene blue (MB) under UV-Vis and visible light irradiation. It was found that the photocatalytic activity of the ZnO/Cu₂O NRs was higher than the ZnO/ZnO NRs under UV-Vis light. In a word, Cu₂O played an important role in enhancing the photocatalytic activity of the ZnO/Cu₂O NRs.     

Influence of lanthanum precursors on the heterogeneous La/SnO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript> nanocatalyst with enhanced catalytic activity under visible light

Surfactant controlled synthesis of La/SnO₂–TiO₂ nanocomposite was studied by using anionic surfactant dioctyl sulfosuccinate sodium salt (DOSS) synthesized via sol–gel method followed by hydrothermal method by using different lanthanum precursors. The structural investigation, thermal degradation, kinetics, thermodynamics properties, crystallite size, morphology, surface and photocatalytic properties of synthesized samples were studied by using different characterization techniques i.e. Thermogravimetric analysis (TGA), Fourier transform-infrared spectroscopy (FTIR), Particle Size Analyzer (PSA), Powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Ultraviolet–Visible spectrophotometer (UV–VIS). Band gap calculations and optical properties of both SnO₂–TiO₂ and La/SnO₂–TiO₂ were studied by using UV–Visible spectroscopy. The performance of both SnO₂–TiO₂ and La/SnO₂–TiO₂ nanocomposites as a photocatalytic agent was also investigated for the degradation of methylene blue (MB) under the illumination of sunlight.