A unique Cu2O/TiO2 nanocomposite with enhanced photocatalytic performance under visible light irradiation

A unique Cu₂O/TiO₂ nanocomposite with high photocatalytic activity was synthesized via a two-step chemical solution method and used for the photocatalytic degradation of organic dye. The structure, morphology, composition, optical and photocatalytic properties of the as-prepared samples were investigated in detail. The results suggested that the Cu₂O/TiO₂ nanocomposite is composed of hierarchical TiO₂ hollow microstructure coated by a great many Cu₂O nanoparticles. The photocatalytic performance of Cu₂O/TiO₂ nanocomposite was evaluated by the photodegradation of methylene blue (MB) under visible light, and compared with those of the pure TiO₂ and Cu₂O photocatalysts synthesized by the identical synthetic route. Within 120 min of reaction time, nearly 100% decolorization efficiency of MB was achieved by Cu₂O/TiO₂ photocatalyst, which is much higher than that of pure TiO₂ (26%) or Cu₂O (32%). The outstanding photocatalytic efficiency was mainly ascribed to the unique architecture, the extended photoresponse range and efficient separation of the electron-hole pairs in the Cu₂O/TiO₂ heterojunction. In addition, the Cu₂O/TiO₂ nanocomposite also retains good cycling stability in the photodegradation of MB.     

Synergic effect of cation doping and phase composition on the photocatalytic performance of TiO2 under visible light

The synergic effect of cation doping and phase composition for the further improvement of the photocatalytic activity of TiO₂ under visible light is reported for the first time. Fe^3 + and Sn^4 + co-doped TiO₂ with optimized phase composition were synthesized through a simple soft-chemical solution method. The visible-light-driven photocatalytic activity of Fe^3 + and Sn^4 + co-doped TiO₂ was 5 times of that of Evonik P25 TiO₂ using degradation of methylene blue as model reaction. The synthesized photocatalysts were characterized by powder X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, ¹¹⁹Sn Mössbauer spectroscopy, and X-ray absorption fine structure spectroscopy. It is indicated that Sn^4 + doping can facilitate the phase transition from anatase to rutile. The different ratios of anatase and rutile can be achieved by tuning the amount of Sn^4 + doped into the lattice. Furthermore, the doping of Sn^4 + into TiO₂ lattice can stabilize the phase composition when Fe^3 + is co-doped. In the Fe^3 + and Sn^4 + co-doped TiO₂, Sn^4 + is mainly used to tune and stabilize the phase composition of TiO₂ and Fe^3 + acts as a doping cation to narrow the band gap of TiO₂. Both band gap and phase composition of TiO₂ can be tuned effectively by the simultaneous introduction of Fe^3 + and Sn^4 +. The synergic effect of optimized phase composition (anatase/rutile = 25/75) and narrowed band gap should be the two main reasons for the promoted photocatalytic activity of TiO₂ under visible light.     

Enhancement of the photocatalytic performance of Ni-loaded TiO2 photocatalyst under sunlight

A highly sunlight active Ni-loaded TiO₂ nanocomposite (Ni/TiO₂) is successfully prepared by a simple chemical reduction method using tetrabutyl titanate as a precursor, Ni(NO₃)₂·6H₂O as a nickel source, and N₂H₄·H₂O as a reductant, respectively. The crystal structure, morphology and UV–vis diffuse reflectance characteristics are investigated by XRD, TEM, and UV–vis diffuse reflectance spectroscopy, while the photocatalytic performance of Ni/TiO₂ is evaluated by photocatalytic degradation of methyl orange solution under UV and sunlight irradiation. Results show that the crystal structure of TiO₂ is not changed upon the loading of Ni, the photocatalytic performance of TiO₂ under both UV-light and sunlight, however, is enhanced greatly. The enhancement of the photocatalytic performance of Ni/TiO₂ is attributed to the increase of the photogenerated electron–hole separation efficiency and the advanced absorption of light due to surface plasmon effect of Ni nanoparticles.     

Fullerene modification CdSe/TiO2 and modification of photocatalytic activity under visible light

CdSe, CdSe-TiO₂, and CdSe-C₆₀/TiO₂ composites were prepared using sol–gel method, and their photocatalytic activity was evaluated by measuring the degradation of rhodamine B solutions under visible light. The surface area, surface structure, crystal phase, and elemental identification of these composites were characterized by nitrogen adsorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and UV-visible (vis) absorption spectrophotometry. XRD showed that the CdSe-C₆₀/TiO₂ composite contained a typical single and clear anatase phase. SEM of the CdSe-C₆₀/TiO₂ composites revealed a homogenous composition in the particles. EDX revealed the presence of C and Ti with strong Cd and Se peaks in the CdSe-C₆₀/TiO₂ composite. The degradation of dye was determined by UV–vis spectrophotometry. An increase in photocatalytic activity was observed and attributed to an increase in the photoabsorption effect by fullerene and the cooperative effect of the CdSe. The repeatability of photocatalytic activity was also tested in order to investigate the stability of C₆₀ and CdS-C₆₀/TiO₂ composites.     

Graphene modified Nd/TiO2 photocatalyst for methyl orange degradation under visible light irradiation

A novel nanoscale GR–Nd/TiO₂ composite photocatalyst was synthesized by the hydrothermal method. Its crystal structure, surface morphology, chemical composition and optical properties were studied using XRD, TEM, and XPS, DRS and PL spectroscopy. It was found that graphene and neodymium modification shifts the absorption edge of TiO₂ to visible-light region. The results of photoluminescence (PL) emission spectra show that GR–Nd/TiO₂ composites possess better charge separation capability than do Nd/TiO₂ and pure TiO₂. The photocatalytic activity of prepared samples was investigated by degradation of methyl orange (MO) dye under visible light irradiation. The results show that the GR–Nd/TiO₂ composite can effectively photodegrade MO, showing an impressive photocatalytic activity enhancement over that of pure TiO₂. The enhanced photocatalytic activity of the composite catalyst might be attributed to the large adsorptivity of dyes, extended light absorption range and efficient charge separation due to Nd doping and graphene incorporation.     

Fabrication of nitrogen-doped TiO2 monolith with well-defined macroporous and bicrystalline framework and its photocatalytic performance under visible light

In this study, hierarchically porous bicrystalline nitrogen-doped titania (N-doped TiO₂) monolithic material was fabricated by a simple two-step approach: (i) preparation of TiO₂ porous monolith by a sol–gel process of titanium alkoxide in a mild condition utilizing a chelating agent and mineral salt and (ii) annealing of TiO₂ porous monolith obtained under a modest flow of ammonia gas at 700 °C for 2 h. The phase composition, crystal structure, morphology, pore structure, and porous properties of the final product were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury porosimetry, and nitrogen physisorption measurement, respectively. The resultant N-doped TiO₂ porous monolith possesses a bicrystalline (anatase and rutile) framework with a well-defined macroporosity. The results from X-ray photoelectron spectroscopy (XPS) confirm the formation of OTiN bonds in the N-doped TiO₂ porous monolith. The photocatalytic activity of N-doped TiO₂ porous monolith was evaluated by the photodegradation of Rhodamine B over the samples under visible light. Nearly 50% of Rhodamine B in aqueous solution was efficiently degraded by N-doped TiO₂ porous monolith with the mixed-phase of anatase and rutile under visible light within 120 min.     

掺钒二氧化钛的可见光催化性能研究

制备高活性可见光响应型掺钒TiO2光催化剂,以荧光灯为光源,光催化降解亚甲基蓝为模型反应,对可见光下TiO2的催化活性进行评价。研究了掺钒TiO2制备方法、掺钒量及氧化剂对光催化氧化的影响。结果表明,溶胶-凝胶法制备的TiO2催化活性较高,且工序简单,钒离子掺杂均匀;掺钒能使TiO2具有可见光响应,最佳掺钒量为1%;外加氧化剂H2O2能提高掺钒TiO2催化活性。     

Bi_2MoO_6/FACs复合光催化剂的制备及其可见光催化性能的研究

以十二烷基苯磺酸钠(SDBS)为表面活性剂,运用水热法制备花状钼酸铋(Bi_2MoO_6),以粉煤灰漂珠(FAC)为载体,制备漂浮型Bi_2MoO_6/FACs复合材料。利用X射线衍射仪、扫描电子显微镜、傅里叶变换红外光谱仪和紫外可见漫反射对样品的晶型、形貌和光响应进行表征,研究Bi_2MoO_6/FACs对四环素的可见光催化活性,并对其光催化机理进行了探讨。结果显示,花状Bi_2MoO_6具有层状奥里维里斯结构,负载在FACs的表面;在实验温度为室温,300 W氙灯模拟可见光照射下,0.015 g复合材料在90 min内对体积50 mL、浓度15 mg/L的四环素溶液的光降解率达81%。     

Efficient hydrogen production by photocatalytic water-splitting using Pt-doped TiO2 hollow spheres under visible light

Pt doped TiO₂ hollow spheres (Pt/HS-TiO₂) are prepared by a sol–gel method and characterized by XRD, SEM, TEM and UV-visible absorption spectra. In addition, Pt/HS-TiO₂ is employed as the catalyst for photocatalytic hydrogen production from water splitting under visible light irradiation. The results show that Pt/HS-TiO₂ with hollow sphere structure presents excellent photocatalytic hydrogen evolution performance. The hydrogen generation rate can reach more than 1023.71 μmol h⁻¹ g⁻¹ at room temperature and no obvious deactivation is observed after 30 h irradiation. Furthermore, the reactively of Pt/HS-TiO₂ could be reproduced in the repeated cycle. Therefore, Pt/HS-TiO₂ is a promising photocatalyst to efficiently generate hydrogen under visible-light irradiation at room temperature.     

Photocatalytic performance of plasma sprayed Pt-modified TiO2 coatings under visible light irradiation

Plasma sprayed Pt/TiO₂ coatings were prepared by Atmospheric Plasma Spraying process. As-sprayed coatings were characterized by TEM, XRD and XPS. The photocatalytic performance was evaluated through the photo mineralization of methylene blue. All the Pt modified titanium dioxide coatings show significant absorption in the visible light range, while the pure titania coating reflects almost all the visible light. The photocatalytic efficiencies of as-sprayed pure TiO₂ coating and Pt/TiO₂ coatings are almost same under the irradiation of visible light. However, the efficiencies of all Pt/TiO₂ coating are greatly improved comparing with that of pure TiO₂ coating by applying 15 V external bias under the irradiation of visible light.     

LED可见光下Au/TiO2光催化氧化甲醛表观动力学

甲醛是室内空气中典型的挥发性有机化合物（VOCs）之一。等离子激元型光催化剂可吸收可见光,可在室温常压下利用太阳光驱动光催化氧化脱除室内空气中甲醛的反应,其表观反应动力学研究对设计等离子激元型光催化剂及应用于脱除VOCs等污染物具有重要意义。研究了LED可见光下等离子激元型Au/TiO₂光催化脱除气相中甲醛的表观反应动力学,考察不同波长的可见光源、光强及反应气相对湿度对表观反应动力学的影响,根据对实验数据的分析求得LED可见光催化氧化甲醛表观反应速率常数k（I,H）。结果表明,在13%相对湿度、蓝光光强为38.5 mW·cm^-2的条件下,光反应的甲醛转化率达77%,是暗反应的近5倍。在LED红、绿、蓝、白光照射下,随着光强增加,甲醛转化率快速增加后缓慢增至基本不变。相同光强（低于42 mW·cm^-2）和湿度条件下,红、绿、蓝光源的甲醛转化率相近,白光略低于其他光源。干气氛下,光反应和暗反应的甲醛转化率几乎为0。湿气氛下,光反应和暗反应均有甲醛转化率,光反应的甲醛转化率更高。不同光源条件下甲醛转化率随相对湿度变化规律相似。相对湿度为21.9%时甲醛转化率最高,而后保持不变,基本在80%左右。通过对红、绿、蓝、白光的数据拟合计算,得到表观动力学参数k（I）_H、k（H）_I、k（I,H）以及速率方程。     

WS2 sensitized mesoporous TiO2 for efficient photocatalytic hydrogen production from water under visible light irradiation

Nanosized WS₂ sensitized mesoporous titanium dioxide (TiO₂) was prepared to extend the adsorption of the wide band gap TiO₂ into visible light region. Compared with TiO₂ substrate without mesopores, it was found that the mesoporous substrate is beneficial for larger amount of WS₂ loading and inhibition of the light-induced detachment of WS₂ particles from the substrate during photocatalytic reaction, which leads to higher photocatalytic activity and better stability. We also found that the rate-determining step for photocatalytic hydrogen production is the transfer of electrons from TiO₂ substrate to H⁺ in solution, when the recombination between electrons and holes within TiO₂ could be neglected. In this case, deposition of Pt at the surface of semiconductor is indispensable for efficient hydrogen production.     

Silver-modified TiO2 nanorods with enhanced photocatalytic activity in visible light region

Silver-modified TiO₂ nanorods (SMTN) have been synthesized via controlled hydrolysis of tetrabutyltitanate (TBOT) in ethanol and immersion method by using AgNO₃ as an Ag source. The physical and chemical properties of SMTN were studied by XRD, SEM, TEM, and UV–vis diffuse reflectance spectra (DRS). The photocatalytic activity of the as-prepared products was evaluated by photocatalytic decolorization of Rhodamine B (Rh B) aqueous solution at ambient temperature under visible light irradiation. The experimental results reveal that the TiO₂ nanorods, which are well dispersed and uniform, attached large numbers of silver nanoparticles on the surface, and the major crystalline phase of TiO₂ is anatase. The photocatalytic activity research shows that the SMTN exhibit an enhanced photocatalytic activity in visible light region compared with that of pure TiO₂ nanorods and commercial TiO₂ (P25).     

Copper reduced defective TiO2 nanoparticles with enhanced visible light photocatalytic activity

Defective TiO₂ attracted increasing attention due to its high photocatalytic activities. Herein, we report a facile and efficient method to fabricate gray defective TiO₂ by vacuum annealing raw TiO₂ materials with copper powders. The treated TiO₂ nanoparticles exhibit significantly enhanced visible‐light‐photocatalytic performance with photo‐degradation rate increased to 400% as that of pristine commercial P25 under visible light. The performance enhancements can be attributed to the disordered structure, optimized optical and electronic properties of defective TiO₂. In addition, this facile Cu reduction method provides an effective way to generate defective sites in other metal oxides for various potential applications.     

Yttrium -barium oxide as a robust photocatalyst for photocatalytic degradation of organic dyes under visible light

Based on the structure related to the high-temperature superconductor yttrium-barium-copper oxide, two novel high-efficiency visible light photocatalysts were created in this study. The yttrium-barium oxide (YBO) semiconductors Y₂Ba₃O₆ (YB3O) and Y₂Ba₄O₇ (YB4O) were prepared by a copper-free solid-phase sintering method. They were applied for the effective treatment of dye-containing wastewater by photocatalysis under visible light irradiation. The degradation efficiency of methylene blue (MB) reached more than 95% within 10 min. Stable visible light degradation of methyl orange (MO) was achieved in the presence of YB3O and YB4O. The electron spin resonance technique and active substance capture technique confirmed the presence of superoxide radicals (·O₂^?), hydroxyl radicals (·OH) and holes (h_VB⁺) under visible light illumination. UV–Vis diffuse reflectance spectroscopy analysis showed that the direct optical band gaps of YB3O and YB4O were 2.550 eV and 2.583 eV, respectively, which resulted in their high visible absorption at 486.27 nm and 480.06 nm. After five cycles, the recoveries of YB3O and YB4O reached 67.15% and 72.98%. Therefore, YB3O and YB4O are considered as powerful semiconductor catalysts for the photocatalytic degradation of organic dyes in wastewater.     

Construction of CoS/CeO2 heterostructure nanocages with enhanced photocatalytic performance under visible light

Exploring non-noble metal photocatalysts with high activity and stability is always fascinating. Herein, the hollow CoS nanocages deriven from ZIF-67 have been reported for the first time to combine with CeO₂ NPs grown in situ for photocatalytic degradation of stubborn pollutants. The unique CoS nanocages not only provide rich active sites but also enhance light capture. CeO₂ NPs loaded on the surface accelerate the separation of photocharges and extend the lifetime of photogenerated carriers. The optimized photocatalysts show outstanding activity and stability for the photodegradation of tetracycline and phenol under visible light, and the corresponding photodegradation efficiency is 96.5% and 90.5% at 60 minutes. The novel multi-stage nanocage structure simultaneously realizes extended light absorption and improved photocharges transfer efficiency. This work provides an exclusive perspective to design high-efficiency photocatalysts with hollow structures for environmental restoration.     

Facile preparation of flake-like blue TiO2 nanorod arrays for efficient visible light photocatalyst

Different kinds of oriented TiO₂ nanorod arrays have been actively pursuing in recent years, however, these fabrications relied on the substrates, such as fluorine-doped tin oxide glass (FTO), silicon wafer or other semiconductor precursor layer. Herein, a stable Ti³⁺ and oxygen vacancies doped blue TiO₂ flakes composed of oriented nanorod arrays were synthesized using a facile hydrothermal treatment in diluted hydrochloric acid solution. Such centimeter-scale flake-like TiO₂ product was obtained without any substrate. Since Ti³⁺ self-doped and/or oxygen vacancies TiO₂ could extend the absorption range of TiO₂ to visible light region, the blue TiO₂ sample exhibited excellent photocatalytic activity under visible light irradiation (photocatalytic degradation efficiency can nearly reach up to 100% within 60?min).     

Preparation, characterization and photocatalytic behavior of WO3-fullerene/TiO2 catalysts under visible light

WO3-treated fullerene/TiO2 composites (WO3-fullerene/TiO2) were prepared using a sol-gel method. The composite obtained was characterized by BET surface area measurements, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and UV-vis analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. Excellent photocatalytic degradation of a MO solution was observed using the WO3-fullerene, fullerene-TiO2, and WO3-fullerene/TiO2 composites under visible light. An increase in photocatalytic activity was observed, and WO3-fullerene/TiO2 has the best photocatalytic activity; it may attribute to the increase of the photo-absorption effect by the fullerene and the cooperative effect of the WO3.     

Iron-doped TiO2 nanotubes with high photocatalytic activity under visible light synthesized by an ultrasonic-assisted sol-hydrothermal method

A series of iron-doped anatase TiO₂ nanotubes (Fe/TiO₂ NTs) catalysts with iron concentrations ranging from 0.88 to 7.00 wt% were prepared by an ultrasonic-assisted sol-hydrothermal process. The structures and the properties of the fabricated Fe/TiO₂ NTs were characterized in detail and photocatalytic activity was examined using a reactive brilliant red X-3B aqueous solution as pollutant under visible light. The lengths of the NTs were determined to range from 20 nm to 100 nm. The incorporation of the iron ions (Fe³⁺) into the TiO₂ nanotubes shifted the photon absorbing zone from the ultraviolet (UV) to the visible wavelengths, reducing the band gap energy from 3.2 to 2.75 eV. The photocatalytic activity of the Fe/TiO₂ NTs was 2–4 times higher than the values measured for the pure TiO₂ nanotubes.