Enhanced visible light photocatalytic activity of Zn2SnO4 via sulfur anion-doping

Sulfur anion doped Zn₂SnO₄ was prepared by calcining the mixture of thiourea and spinel Zn₂SnO₄ at 300 °C under argon atmosphere and characterized by XRD, XPS and DRS. It was found that S^2? was incorporated interstitially into the bulk phase of Zn₂SnO₄. After the doping of S^2?, the band gap of Zn₂SnO₄ was sharply decreased to 2.7 eV compared with that of undoped Zn₂SnO₄ (~ 3.6 eV). The photocatalytic activity of S-doped Zn₂SnO₄ was enhanced for photodegradation of Rhodamine B (RhB) in aqueous solution under visible light irradiation.     

Synthesis of Cu2O/T-ZnOW nanocompound and characterization of its photocatalytic activity and stability property under UV irradiation

Cu₂O/tetrapod-like ZnO whisker (T-ZnO_W) nanocompound was synthesized by a simple hydrothermal chemical method. The chemical composition, morphology, band gap and photocatalytic property of the Cu₂O/T-ZnO_W nanocompound were studied in detail. It was observed that the Cu₂O particles deposited on T-ZnO_W surface had a cubic structure and the crystallinity of T-ZnO_W did not change with the increase of Cu₂O crystals. The morphology and content of Cu₂O in the Cu₂O/T-ZnO_W nanocompound played an important role on the photocatalytic activity. In addition, the coexistence of Cu₂O and T-ZnO_W nanoparticles was propitious to the high photocatalytic activity owing to their hetero-junction effect. The Cu₂O/T-ZnO_W nanocompound prepared by 7.2% Cu/Zn MR exhibited the best photocatalytic activity on the degradation of MO solution under UV light irradiation. At the first 100 min of irradiation, the photodegradation efficiency of MO solution reached up to 99.16%, which still retained its high photocatalytic activity about 89.10% even at the end of the fourth cycle. Little change was found in their phase compositions after the photocatalytic reaction process, except partial oxidation of particles’ surface. The mechanism for UV light driven photocatalytic activity enhancement over Cu₂O/T-ZnO_W nanocompound was discussed.     

Hydrothermal synthesis of SnO2/SnS2 nanocomposite with high visible light-driven photocatalytic activity

SnO₂/SnS₂ nanocomposite with a heterojunction structure (that is, SnO₂ nanoparticles-decorated SnS₂ nanoplates) was synthesized via the hydrothermal reaction between SnO₂ nanoparticles and thioacetamide in 5 vol.% acetic acid aqueous solution at 150 °C for 3 h, and characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and UV–vis diffuse reflectance spectra. The photocatalytic activity of the hydrothermally synthesized SnO₂/SnS₂ nanocomposite was tested by degrading methyl orange in distilled water under visible light (λ > 420 nm) irradiation. It was found that the hydrothermally synthesized SnO₂/SnS₂ nanocomposite exhibited superior photocatalytic activity to SnO₂ nanoparticles, SnS₂ nanoplates and physically mixed SnO₂/SnS₂ nanocomposite. The heterojunction structure of the hydrothermally synthesized SnO₂/SnS₂ nanocomposite, which can facilitate interfacial electron transfer and reduce the self-agglomeration of two components, was considered to play an important role in achieving its higher photocatalytic activity.     

Facile synthesis and characterization of ZnO NPs,ZnO/CdO and ZnO/SnO2 nanocomposites for photocatalytic degradation of Eosin Yellow and Direct Blue 15 under UV light irradiation

Journal of Materials Science: Materials in Electronics - In the present report, the synthesis of ZnO NPs, ZnO/CdO NCs, and ZnO/SnO2 NCs was successfully achieved by co-precipitation technique. The...     

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.     

Structural and magnetic properties of nanocrystalline Fe-doped SnO2

Single phase Sn_1?xFe_xO₂ (x = 0.1, 0.3 and 0.5) nanoparticles having size in the range 9–17 nm were prepared by a chemical route. XRD analysis of the samples confirmed the formation of cassiterite phase without any impurity. The nanocrystalline nature of the samples and their crystallinity were confirmed by TEM measurements. Raman and Mössbauer spectroscopy studies indicate structural disorder and vacancies in the nanostructures. M–H and M–T data recorded by a SQUID magnetometer show that the samples are essentially paramagnetic with a weak ferromagnetic component. Ferromagnetism is argued to be associated with the vacancies and defects present in the grain boundaries and interfaces of the nanoparticles.     

铍、氮共掺杂TiO2的制备及其可见光下光解水制氢性能研究

通过煅烧硫酸钛与氨水水解沉淀物制备氮掺杂TiO2(N-TiO2),用浸渍法制备了铍、氮共掺杂TiO2光催化剂(Be-N-TiO2).通过可见光光还原沉积法载铂,以可见光(λ≥420nm)光催化制氢为探针反应考察了催化剂的活性,发现当煅烧温度为300℃,Be2 的掺杂量为1.5%(原子分数)时,制备的Pt/Be-N-TiO2制H2活性最高.通过XRD、DRS、FT-IR等手段对掺杂催化剂进行了表征,N掺杂可在TiO2中形成O-Ti-N键,使其具有可见光吸收能力;掺入Be2 可以有效的分离光生电子和空穴,减少了两者的复合,同时能够消除由于氮掺杂引入的氧空位,使共掺杂催化剂相对于单一的N-TiO2具有较高的可见光制H2活性.     

Enhanced photocatalytic performance of CuFeO2-ZnO heterostructures for methylene blue degradation under sunlight

One of the strategies to overcome the drawbacks of fast charge recombination of a photocatalyst is to develop semiconductor heterostructures. Herein, we report a two-step precipitation-hydrothermal process to create CuFeO₂-ZnO heterostructures with different weight percentages of CuFeO₂ (0.5, 1, 5, and 10%). Though X-ray diffraction detected the presence of CuFeO₂ on ZnO above 5%, Raman spectroscopy could reveal the presence of CuFeO₂ phase as low as 0.5 wt%. For all of the compositions, the bandgap of ZnO did not vary (3.15 eV) on forming heterostructures with CuFeO₂. The oxidation of methylene blue under sunlight was used to determine the photocatalytic performance of the heterostructures. In comparison to pure ZnO and CuFeO₂, CuFeO₂-ZnO heterostructures exhibited a better photocatalytic efficiency. Overall, 5 wt% CuFeO₂ on ZnO showed 100% degradation with a rate constant of 0.272?±?0.002 min^?1, which is 16 times faster than ZnO. Time-resolved photoluminescence analysis indicated a higher lifespan of charge carriers in the 5wt% CuFeO₂-ZnO heterostructure (32.3 ns) than that of CuFeO₂ (0.85 ns) and ZnO (27.6 ns). The Mott–Schottky flat band potentials of ZnO and CuFeO₂ was determined to be -0.82 and 1.17 eV, respectively, revealing the presence of Type I heterostructures. The heterostructures also showed outstanding recyclability, with a degradation rate of 97% even after four cycles. The current study shows the significance of forming p-type CuFeO₂ and n-type ZnO heterostructures for enhanced photocatalysis.

     

Heterostructured bismuth molybdate composite: preparation and improved photocatalytic activity under visible-light irradiation

A heterostructured photocatalyst containing the same Bi, Mo, and O elements (Bi(3.64)Mo(0.36)O(6.55)/Bi(2)MoO(6)) was realized by a facile hydrothermal method. The heterostructured composite was characterized by powder X-ray diffraction, selected-area electron diffraction, scanning electron microscopy, and high-resolution electron microscopy. The Bi(3.64)Mo(0.36)O(6.55)/Bi(2)MoO(6) composite exhibited notable enhanced photocatalytic activity compared to Bi(2)MoO(6) or Bi(3.64)Mo(0.36)O(6.55) in the photocatalytic degradation of rhodamine B and phenol under visible-light irradiation. More interestingly, it is found that the heterostructured composite could mineralize organic substances into CO(2) efficiently. This study offered a clue for the design of an efficient photocatalyst in the application of environmental treatment.     

非金属元素掺杂TiO2的可见光催化活性研究进展

TiO2(锐钛矿)的禁带宽度限制了其光诱导特性的广泛应用,非金属元素掺杂为TiO2在可见光辐射环境下的应用提供了新的机会.详细介绍了非金属元素(N、C、S、F)掺杂TiO2的制备方法和可见光催化活性研究的最新进展,讨论了制备工艺与掺杂TiO2可见光催化活性的关系,深入分析了非金属元素对TiO2可见光催化活性的诱导机理.制备工艺显著影响了掺杂元素的化学态和含量,从而决定了掺杂TiO2带隙中局域态的特征.带隙中局域态特征正是影响掺杂TiO2可见光催化活性的关键因素.文章也对未来的研究方向进行了展望.     

Facile synthesis of Ag/ZnO heterostructures assisted by UV irradiation: Highly photocatalytic property and enhanced photostability

We report a new method to synthesize Ag/ZnO heterostructures assisted by UV irradiation. The formation of Ag/ZnO heterostructures depends on photogenerated electrons produced by ZnO under UV light to reduce high valence silver. Functional property of the Ag/ZnO heterostructures is evaluated by photodegradation of methylene blue (MB) under UV illumination. Results of photodegradation tests reveal that the optimal photocatalytic activity of as-syntheszied samples is about 1.5 times higher than the pure ZnO synthesized in the same condition or commercial TiO₂ (P-25), showing the advantage of the unique structure in the Ag/ZnO heterostructure. Besides, due to the reduced activation of surface oxygen atom, photocatalytic activity of the photocatalysts has no evident decrease even after three recycles.     

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.     

TiO2 mediated photocatalytic degradation studies of Reactive Red 198 by UV irradiation

Photocatalytic degradation of an aqueous solution of azo dye (Reactive Red 198) used in textile industries by UV irradiation was investigated. The effect of initial dye concentration, TiO(2) loading, pH and H(2)O(2) on degradation rate was ascertained and optimized conditions for maximum degradation were determined. The kinetics of photocatalytic degradation was found to follow a pseudo-first order according to Langmuir-Hinshelwood model. The degradation experiment under optimized reaction conditions was investigated under sunlight.     

Hydrothermal synthesis and photocatalytic activity of CdO2 nanocrystals

CdO(2) nanocrystals with different sizes were synthesized via the hydrothermal reaction of 3CdSO(4).8H(2)O and H(2)O(2) in 1.25-6.25 vol.% ammonia solutions at 100-140 degrees C for 12h. The resultant products were characterized by powder X-ray diffraction, transmission electron microscope, thermal gravimetric and differential scanning calorimetry, and UV-vis absorption spectra. It was concluded that the resultant products were pure cubic phase CdO(2) nanocrystals, and they would decompose at temperatures higher than 180 degrees C. In addition, degradation of methyl orange in aqueous solution (20.0mg/l) was carried out with the CdO(2) nanocrystals as photocatalyst under ultraviolet light irradiation. The experimental results showed that even a little amount (0.2g) of as-prepared CdO(2) nanocrystals could catalyze degradation of 500 ml methyl orange solution above 99% after 5h of illumination, and smaller size made for higher photocatalytic activity of CdO(2) nanocrystals.     

Preparation of Bi2Ti2O7/TiO2 nanocomposites and their photocatalytic performance under visible light irradiation

To improve visible-light-driven photocatalytic activity of TiO₂, the octahedral Bi₂Ti₂O₇ nanoparticles have been successfully supported on TiO₂ nanotubes (Bi₂Ti₂O₇/TiO₂) for the first time by a simple hydrothermal method. The structure and electro-optical property of the Bi₂Ti₂O₇/TiO₂ were characterized in detail. The obtained Bi₂Ti₂O₇/TiO₂ exhibited a markedly enhanced photocatalytic activity and good stability for degradation of organic pollutants under visible light. The study presents a new way to synthesize Bi₂Ti₂O₇/TiO₂ using TiO₂ nanotubes as both supporter and reactant.