Pt-Chitosan-TiO2 for Efficient Photocatalytic Hydrogen Evolution via Ligand-to-Metal Charge Transfer Mechanism under Visible Light

The Pt-chitosan-TiO₂ charge transfer (CT) complex was synthesized via the sol-gel and impregnation method. The synthesized photocatalysts were thoroughly characterized, and their photocatalytic activity were evaluated toward H₂ production through water reduction under visible-light irradiation. The effect of the preparation conditions of the photocatalysts (the degree of deacetylation of chitosan, addition amount of chitosan, and calcination temperature) on the photocatalytic activity was discussed. The optimal Pt-10%DD75-T200 showed a H₂ generation rate of 280.4 μmol within 3 h. The remarkable visible-light photocatalytic activity of Pt-chitosan-TiO₂ was due to the CT complex formation between chitosan and TiO₂, which extended the visible-light absorption and induced the ligand-to-metal charge transfer (LMCT). The photocatalytic mechanism of Pt-chitosan-TiO₂ was also investigated. This paper outlines a new and facile pathway for designing novel visible-light-driven photocatalysts that are based on TiO₂ modified by polysaccharide biomass wastes that are widely found in nature.     

Construction of 2D-2D TiO2 nanosheet/layered WS2 heterojunctions with enhanced visible-light-responsive photocatalytic activity

Constructing nanocomposites that combine the advantages of composite materials, nanomaterials, and interfaces has been regarded as an important strategy to improve the photocatalytic activity of TiO₂. In this study, 2D-2D TiO₂ nanosheet/layered WS₂ (TNS/WS₂) heterojunctions were prepared via a hydrothermal method. The structure and morphology of the photocatalysts were systematically characterized. Layered WS₂ (～4 layers) was wrapped on the surface of TiO₂ nanosheets with a plate-to-plate stacked structure and connected with each other by W=O bonds. The as-prepared TNS/WS₂ heterojunctions showed higher photocatalytic activity for the degradation of RhB under visible-light irradiation, than pristine TiO₂ nanosheets and layered WS₂. The improvement of photocatalytic activity was primarily attributed to enhanced charge separation efficiency, which originated from the perfect 2D-2D nanointerfaces and intimate interfacial contacts between TiO₂ nanosheets and layered WS₂. Based on experimental results, a double-transfer photocatalytic mechanism for the TNS/WS₂ heterojunctions was proposed and discussed. This work provides new insights for synthesizing highly efficient and environmentally stable photocatalysts by engineering the surface heterojunctions.     

g-C3N4/Ag/TiO2复合材料的构筑及其光催化性能（英文）

以合成的g-C3N4纳米片和Ag/TiO2空心微球为原料,采用机械搅拌的方法构筑了g-C3N4/Ag/TiO2三元复合光催化剂。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、X射线光电子能谱(XPS)、紫外-可见光漫反射(UV-Vis DRS)和光致发光光谱(PL)对g-C3N4/Ag/TiO2进行了表征。研究表明,g-C3N4/Ag/TiO2是由Ag/TiO2微球和g-C3N4纳米片复合而成的。与TiO2相比,其可见光响应范围延长,光生载流子的分离速率加快。在室温下,用降解罗丹明B的反应考察了g-C3N4/Ag/TiO2的可见光催化活性。研究表明,光照180 min时,g-C3N4(0.5%)/Ag/TiO2显示了最高的光催化活性(91.9%),分别是TiO2和Ag/TiO2的7.5和1.8倍。光催化活性的提高与合理的异质结构建和Ag的导电性能有关。     

Degradation of organic compounds on TiO<Subscript>2</Subscript> photocatalysts prepared by a hydrothermal method in the presence of NH<Subscript>4</Subscript>F

TiO₂ photocatalysts were synthesized by a hydrothermal method from tetraisopropyl orthotitanate (TPOT) in the presence of NH₄F with different NH₄F/Ti molar ratios (0, 0.25, and 1). The formation of a well-crystallized anatase phase of TiO₂ and the suppression of phase transition to rutile were observed, even at high calcination temperature, owing to the effects of NH₄F. The TiO₂ synthesized hydrothermally with NH₄F exhibited absorption with a shift to the longer wavelengths of the visible-light region. The hydrothermally synthesized TiO₂ with a moderate amount of NH₄F exhibited high photocatalytic activity for the degradation of alcohol diluted in water under both UV-light and visible-light irradiations.     

Control of Spatially Homogeneous Distribution of Heteroatoms to Produce Red TiO2 Photocatalyst for Visible-Light Photocatalytic Water Splitting

The strong band-to-band absorption of photocatalysts spanning the whole visible-light region (400–700 nm) is critically important for solar-driven photocatalysis. Although it has been actively and widely used as a photocatalyst for various reactions in the past four decades, TiO₂ has a very poor ability to capture the whole spectrum of visible light. In this work, by controlling the spatially homogeneous distribution of boron and nitrogen heteroatoms in anatase TiO₂ microspheres with a predominance of high-energy {001} facets, a strong visible-light absorption spectrum with a sharp edge beyond 680 nm has been achieved. The red TiO₂ obtained with homogeneous doping of boron and nitrogen shows no increase in defects like Ti³⁺ that are commonly observed in doped TiO₂. More importantly, it has the ability to induce photocatalytic water oxidation to produce oxygen under the irradiation of visible light beyond 550 nm and also the photocatalytic reduction of water to produce hydrogen under visible light. These results demonstrate the great promise of using red TiO₂ for visible-light photocatalytic water splitting and also reveal an attractive strategy for realizing the wide-spectrum visible-light absorption of wide-band-gap oxide photocatalysts.     

Exploration of silver decoration concentration to enhance photocatalytic efficiency of titanium dioxide photocatalysts

Ag decoration on TiO₂ is favorable to absorption of visible light and wider absorption range. Ag nanoparticles playing the role of electron receivers on TiO₂ surface enhance photodegradation. However, excess Ag nanoparticles caused reduced specific surface area of photocatalysts and increased probability of charge recombination, resulting in lower photocatalytic efficiency. In this study, the influence of various Ag decoration concentrations on photocatalytic activity was investigated. Surface treatment by nitric acid after Ag decoration was performed to avoid excessive Ag deposition. The extent of Ag elimination and its impacts on photocatalytic activity were also explored. An optimum Ag content in the photocatalyst was achieved and photocatalytic efficiency was obviously improved. It was found that the number of calcination times affected the crystallinity and stability of photocatalysts. Better photocatalytic efficiency could be obtained after twice calcinations.     

Photodegradation of Direct Blue-199 in carpet industry wastewater using iron-doped TiO2 nanoparticles and regenerated photocatalyst

Fe-doped TiO_2, Ti_1–xFe_xO₂ (x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10), photocatalysts have been successfully synthesized via citric acid–assisted autocombustion method. The synthesized photocatalysts were characterized using different characterization techniques, such as X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX), and x-ray photoelectron spectroscopy (XPS). The XRD diffraction patterns revealed that synthesized photocatalysts have the anatase phase of TiO₂. The DRS analysis indicates a slight increment in absorbance in the visible light region by the Fe doping in TiO₂. The FT-IR spectra reveal the various stretching and bending vibrational bands of the Ti–O lattice. The XPS spectra confirm the presence of elements titanium, oxygen, and iron in the synthesized samples and determine binding energy of elements. TEM analysis shows the shape of the synthesized photocatalyst, and it was used to calculate the average particle sizes of undoped and Fe-doped TiO₂ (Ti_0.96Fe_0.04O₂) photocatalysts using a histogram. The photocatalytic activities of synthesized photocatalysts were determined by photodegradation of dye (Direct Blue 199), contaminating carpet industry wastewater in the photochemical reactor and open pan reactor. The maximum photodegradation activity was shown by the Ti_0.96Fe_0.04O₂ photocatalyst among all the synthesized undoped and Fe-doped photocatalysts. The synthesized photocatalyst (Ti_0.96Fe_0.04O₂) had better photocatalytic activity when compared to both, undoped TiO₂ and Aeroxide (Degussa) P-25. The used Fe-doped TiO₂ photocatalyst (Ti_0.96Fe_0.04O₂) was regenerated five times and investigated for its photocatalytic activity.     

Synthesis of sponge-like TiO2 with surface-phase junctions for enhanced visible-light photocatalytic performance

Maximizing adsorption and catalytic active sites and promoting the photo-excited charge separation are two key factors to achieve excellent photocatalytic performance. In this study, we report a sol-gel synthesis approach to obtain non-metal doped TiO₂ with sponge-like structure and surface-phase junctions all at once. While doping of carbon and nitrogen shifted the activation wavelength to the visible-light region, the innovative use of perchloric acid as a pore-making agent led to the formation of three-dimensional lamellar and porous structure with surface-phase junctions. High surface area with catalytic active sites rendered by the sponge-like structure and surface-phase junctions contributed to the much improved photocatalytic degradation efficiency toward rhodamine B, tetracycline and Disperse Red 60 with excellent reusability and stability. The improved generation and separation efficiency of the photo-induced charge carriers of the as-prepared TiO₂ were supported by electrochemical impedance measurements and transient photocurrent responses. This method could also be applied to other photocatalysts to achieve structural alteration and element doping simultaneously.     

Degradation of terbuthylazine by Fe/TiO2 with visible-light-driven photo-Fenton catalytic activity

In order to improve the catalytic activity of Fenton catalyst, a composite catalyst, Fe/TiO₂, with both visible-light photocatalytic and Fenton-like catalytic activities was synthesized via a brief solvothermal process. The XRD and SEM results indicated that Fe was dispersed homogeneously on the surface of TiO₂ in the form of Fe₂O₃, and the loading of Fe did not have significant effects on the particle size and morphology of TiO₂. The EDS results showed that the loading content of Fe was about 1.4 wt%. The photocatalytic results showed that the prepared Fe/TiO₂ composite catalyst had excellent catalytic behaviors for terbuthylazine degradation under visible-irradiation with H₂O₂ assistance, the degradation ratio reached up to 90% after 120 min. The reinforced degradation performance were primarily attributable to the introduction of carrier TiO₂, which expanded visible response range by H₂O₂ adsorption, and accelerated the cycle of Fe (Ⅱ)/Fe (Ⅲ). The fluorescent spectroscopy results revealed that the degradation process of terbuthylazine involved the generation and participation of active species such as hydroxyl radicals and superoxide radicals. This study is expected to provide a visual approach for designing a novel photo-Fenton catalyst to jointly utilize both photocatalytic and Fenton activities, which can be better applied to the actual use of organics purification in wastewater.     

Coal Combustion Synthesis of Coal Cinder-Supported TiO<Subscript>2</Subscript> with Commendable Photocatalytic Activity

Coal cinder-supported TiO₂ photocatalysts were synthesized via a novel coal combustion method. As-obtained samples were characterized by XRD, SEM, EDS mapping, Raman spectra, FTIR and DRS, and their photocatalytic performances were evaluated by degradation of methylene blue (MB) and methyl orange (MO) under UV–Vis light illumination. The results revealed that mixed-phases TiO₂ with adjustable anatase–rutile ratio could be obtained by adjusting the amount of precursor tetrabutyl titanate, which was uniformly covered on the coal cinder. These coal cinder-supported TiO₂ photocatalysts exhibited commendable photocatalytic activity. Among them, the indexed CCT-7.5 sample presented the maximum of activity, which can be attributed to the optimal phase composition of TiO₂. The present work provided a novel synthetic route to fabricate immobilized photocatalysts, which might be extended to the preparation of other functional materials.     

可见光下具有高光子效应和光催化活性的CuS-石墨烯氧化物/TiO2复合材料的制备（英文）

CuS-graphene oxide/TiO2 composites were prepared using a sol-gel method to improve the photocatalytic performance of the photocatalyst. The composites were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, and transmission electron microscopy. The photocatalytic activities were examined by the degradation of methylene blue (MB) under visible-light irradiation. The photodegradation of MB under visible-light irradiation reached 90.1% after 120 min. The kinetics of MB degradation was plotted alongside the values calculated from the Langmuir-Hinshelwood equation. The CuS-graphene oxide/TiO2 sample prepared using 0.2 mol of TiO2 showed the best photocatalytic activity. This was attributed to a cooperative reaction as a result of increased photoabsorption by graphene oxide and an increased photocatalytic effect by CuS.     

Preparation of Ag deposited TiO2 (Ag/TiO2) composites and investigation on visible-light photocatalytic degradation activity in magnetic field

In this study, Ag deposited TiO₂ (Ag/TiO₂) composites were prepared by three different methods (Ultraviolet Irradiation Deposition (UID), Vitamin C Reduction (VCR) and Sodium Borohydride Reduction (SBR)) for the visible-light photocatalytic degradation of organic dyes in magnetic field. And then the prepared Ag deposited TiO₂ (Ag/TiO₂) composites were characterized physically by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The visible-light photocatalytic activities of these three kinds of Ag deposited TiO₂ (Ag/TiO₂) composites were examined and compared through the degradation of several organic dyes under visible-light irradiation in magnetic field. In addition, some influence factors such as visible-light irradiation time, organic dye concentration, revolution speed, magnetic field intensity and organic dye kind on the visible-light photocatalytic activity of Ag deposited TiO₂ (Ag/TiO₂) composite were reviewed. The research results showed that the presence of magnetic field significantly enhanced the visible-light photocatalytic activity of Ag deposited TiO₂ (Ag/TiO₂) composites and then contributed to the degradation of organic dyes.     

Ln掺杂BiVO4(Ln=Eu、Gd、Er)光催化剂的制备和活性研究

采用水热合成法, 制备出Eu、Gd和Er掺杂的BiVO₄复合光催化剂,并采用X射线衍射、X射线光电子谱、扫描电子显微镜和紫外-可见漫反射光谱技术对其进行分析表征。通过可见光下降解水溶液中甲基橙分子来考察其光催化性能,结果显示掺杂的复合光催化剂活性都强于纯的BiVO₄,对掺杂复合光催化剂的催化活性增强机理进行了讨论和描述。     

Synthesis of CuAPTPP-TDI-TiO2 Conjugated Microspheres and its Photocatalytic Activity (cited: 1)

The metal complex 5-(4-aminophenyl)-10,15,20-triphenylporphyrin copper (CuAPTPP) was covalently linked on the surface of TiO₂ microspheres by using toluene disocyanate (TDI) as a bridging bond unit. The hydroxyl group (-OH) of TiO₂ microspheres surface and the amino group (-NH₂) of CuAPTPP reacted respectively with the active -NCO groups of TDI to form a surface conjugated microsphere CuAPTPP-TDI-TiO₂ that was confirmed by FT-IR spectra. The CuAPTPP-TDI-TiO₂ microspheres were characterized with UV-visible, elemental analysis, XRD, SEM, and UV-Vis diffuse reflectance spectra. The effect of amounts of linked TDI on the performance of photocatalytic microspheres was discussed, and the optimal molar ratio of TDI:TiO₂ was established. The photocatalytic activity of CuAPTPP-TDI-TiO₂ was evaluated using the photocatalytic degradation of methylene blue (MB) under visible-light irradiation. The results showed that, TDI, as a bond unit, was used to form a steady chemical brigdging bond linking CuAPTPP and the surface of TiO₂ microspheres, and the prepared catalyst exhibited higher photocatalytic activity under visible-light irradiation for MB degradation. The degradation rate of 20 mg/L MB could reach 98.7% under Xe-lamp (150 W) irradiation in 120 min. The degradation of MB followed the first-order reaction model under visible light irradiation, and the rate constant of 5.1×10^-2 min^-1 and the half-life of 11.3 min were achieved. And the new photocatalyst can be recycled for 4 times, remaining 90.0% MB degradation rate.     

Visible-light-sensitive N-doped TiO<Subscript>2</Subscript> photocatalysts prepared by a mechanochemical method: effect of a nitrogen source

Nitrogen-doped titanium dioxide (N-doped TiO₂) photocatalysts were prepared by a mechanochemical method by using a high-speed ball milling of P25 TiO₂ with nitrogen sources such as ammonia solution, hexamine, and urea. Visible-light absorption was determined from the onset of diffused reflectance spectrum. The photocatalytic activity of the N-doped TiO₂ was evaluated through the removal of methylene blue (MB) under visible-light irradiation. The effects of nitrogen precursors used during the mechanochemical synthesis on the catalysts’ properties, such as the effective particle size, surface area, and photocatalytic activity, were extensively investigated.     

玻璃微珠/Ag/TiO2可见光催化剂的制备与表征

通过离子交换法将Ag纳米颗粒负载于玻璃微珠的表面及浅表层,并以钛酸四丁酯的乙醇溶液为前驱体,将TiO₂负载于包含银的玻璃微珠表面,制得一种玻璃微珠/Ag/TiO₂复合光催化剂。由于纳米银的表面等离子体吸收效应,该复合光催化剂具有一定的可见光响应特性。利用XRD、SEM对样品进行表征,可发现玻璃微珠表面形成一层均匀多孔的锐钛矿TiO₂,其粒径均在50 nm左右。由漫反射光谱可得出该催化剂具有较强的可见光吸收,并在降解甲基橙溶液的试验中表现出较好的可见光催化活性。     

Preparation of TiO2 nano-particle photocatalysts by a multi-gelation method: the effect of pH change

TiO₂ photocatalysts were prepared by a multi-gelation method and the effect of the changes in the pH during the pH swing times, i.e., by a controlled pH swing, on the morphology of the TiO₂ particles was investigated. The photocatalytic properties of the TiO₂ catalysts prepared by controlled pH swing were compared with TiO₂ particles prepared without adjusting the pH during the swing times. The photocatalytic degradation reaction of these TiO₂ catalysts was investigated by comparing their effectiveness in 2-propanol oxidation. The experimental results showed that the TiO₂ photocatalysts prepared without adjusting the pH performed better in controlling the important parameters of the catalysts such as particle size, surface area, anatase/rutile phase ratio and pore size, as well as pore volume than the TiO₂ photocatalysts prepared by a controlled pH swing method. Deceased.     

Preparation and photocatalytic activity of high-efficiency visible-light-responsive photocatalyst SnSx/TiO2

Visible-light-responsive composite photocatalysts SnS₂/TiO₂ and SnS/TiO₂ with different mass ratios were prepared by in-situ synthesis technology in solution with commercial TiO₂. The junction-based materials SnS_x (x=1, 2)/TiO₂ were found to have high visible-light photocatalytic performance and possess much better activity than the single-phase SnS_x or TiO₂. The greatly enhanced photocatalytic activity of the SnS_x/TiO₂ composites was mainly attributed to the matching band potentials and efficient charge transfer and separation at the tight-bonding interface between SnS_x and TiO₂. The fact was confirmed by the comparison of photocatalytic activities of the SnS₂/TiO₂ samples prepared by physical mixing method and in-situ synthesis technique.     

Preparation of nanocrystalline Fe-doped TiO<Subscript>2</Subscript> powders as a visible-light-responsive photocatalyst

Nanocrystalline Fe-doped TiO₂ powders were prepared using TiOSO₄, urea, and Fe(NO₃)₃ · 9H₂O as precursors through a hydrothermal method. The as-synthesized yellowish-colored powders are composed of anatase TiO₂, identified by X-ray diffraction (XRD). The grain size ranged from 9.7 to 12.1 nm, calculated by Scherrer’s method. The specific surface area ranged from 141 to 170 m²/g, obtained by the Brunauer–Emmett–Teller (BET) method. The transmission electron microscopy (TEM) micrograph of the sample shows that the diameter of the grains is uniformly distributed at about 10 nm, which is consistent with that calculated by Scherrer’s method. Fe³⁺ and Fe²⁺ have been detected on the surface of TiO₂ powders by X-ray photoelectron spectroscopy (XPS). The UV–Vis diffuse reflection spectra indicate that the light absorption thresholds of the Fe-doped TiO₂ powders have been red-shifted into the visible light region. The photocatalytic activity of the Fe-doped TiO₂ was evaluated through the degradation of methylene blue (MB) under visible light irradiation. The Fe-doped TiO₂ powders have shown good visible-light photocatalytic activities and the maximum degradation ratio is achieved within 4.5 h.     

Fe2BiTaO7纳米催化剂的组织结构及光催化性能

用固相反应合成法合成了光催化剂Fe₂BiTaO₇,通过XRD、SEM、TEM、紫外-可见漫反射等表征方法对其组织结构及光催化性能进行了研究.结果表明Fe₂BiTaO₇为立方晶系烧绿石结构,空间群为Fd₃m,禁带宽度为1.72eV.通过比较Fe₂BiTaO₇、P₂₅TiO₂、掺氮TiO₂和Bi₂InTaO₇的可见光光催化降解罗丹明B,发现Fe₂BiTaO₇降解效果及催化活性均高于其它催化剂,并且Fe₂BiTaO₇降解罗丹明B效率是掺氮二氧化钛的1.5倍.Fe₂BiTaO₇降解罗丹明B的曲线符合一级动力学,一级动力学常数为0.02293 min^-1.研究了罗丹明B可能的降解路径和Fe₂BiTaO₇在可见光下降解苯酚的效果.Fe₂BiTaO₇(可见光)光催化剂系统适用于纺织工业废水处理.