Effect of nitrogen-doping temperature on the structure and photocatalytic activity of the B,N-doped TiO2

B,N-TiO₂ photocatalysts were synthesized by boron doping firstly and subsequently nitrogen doping in NH₃ at variable temperatures. The effects of the nitrogen doping temperature on the structure and photocatalytic activity of the B,N-codoped TiO₂ were investigated. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectrum (DRS), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated with photocatalytic degradation of methyl orange dye (MO) under visible light and UV-visible light irradiation. The results suggested that the boron and nitrogen can be incorporated into the TiO₂ lattice either interstitially or substitutionally or both, while the Ti-O-B-N structure plays a vital role in photocatalytic activity in visible light region. The optimal nitrogen doping temperature is 550 °C. Higher temperature may form many oxygen vacancies and Ti³⁺ species, resulting in the decrease of photocatalytic activity in visible light.     

Doping level effect on visible-light irradiation W-doped TiO2–anatase photocatalysts for Congo red photodegradation

A series of W-modified TiO₂ (W–TiO₂) photocatalysts were synthesized by a simple sol–gel method. The new photocatalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis-diffuse reflectance spectroscopy (DRS), and Brunauer, Emmett and Teller (BET) surface area analyzer. The photoactivity of the W–TiO₂ photocatalysts was evaluated by the photocatalytic oxidation of Congo red (CR) dye. It was found that the average size of the prepared photocatalysts is 10 nm. Moreover, they have high surface areas (∼ 216 m² g⁻¹) and their light-absorption extends to the visible region compared to pure TiO₂. The effects of W-loading and of the calcination temperature of the prepared photocatalysts on their photocatalytic activity were also studied. The obtained results show that the W_0.5–TiO₂ photocatalyst calcined at 350 °C is much highly photoactive than non-doped or highly doped TiO₂. The enhanced photocatalytic activity of the weakly doped TiO₂ may be attributed to the increase in the charge separation efficiency and the presence of surface acidity on the W_0.5–TiO₂ photocatalyst.     

Simple preparation of Mn–N-codoped titania photocatalyst with visible light response

Mn–N-codoped TiO₂ nanocrystal photocatalysts responsive to visible light were synthesized for the first time by a simple hydrothermal synthesis method. X-ray powder diffraction (XRD) measurement indicated that all the photocatalysts have an anatase crystallite structure, and that increase of the doping concentration had little effect on the structure and particle size. Compared to N-doped TiO₂, a shift of the absorption edge of Mn–N-codoped TiO₂ to a lower energy and a stronger absorption in the visible light region were observed. The Mn–N-codoped TiO₂ showed higher photocatalytic reactivity than undoped TiO₂ or N-doped TiO₂ for the photodegradation of rhodamine B (RhB) under visible light irradiation. The highest photocatalytic activity was achieved on 0.4 mol% Mn–N–TiO₂ calcined at 673 K.     

Hydrothermal synthesis and photocatalytic property of porous CuO hollow microspheres via PS latex as templates

Porous copper oxide (CuO) hollow microspheres have been fabricated through a simple hydrothermal method using PS latex as templates. The as-obtained samples were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). The influences of the mole ratio of Ethylenediamine (C₂H₈N₂) and copper acetate (Cu(Ac)₂·H₂O), hydrothermal temperature and time on the size and morphologies of the final products have been investigated. The possible formation mechanism of porous CuO hollow microspheres has been proposed and the specific surface area of the hollow microspheres with 81.71 m²/g is measured by BET method. The band gap value calculated from a UV–vis absorption spectrum of porous CuO hollow microspheres is 2.71 eV. The as-synthesized product exhibits high photocatalytic activity during the photodegradation of an organic dyestuff, rhodamine B (RhB), under UV-light illumination.     

Sunlight-induced photocatalytic degradation of acetaminophen over efficient carbon doped TiO2 (CTiO2) nanoparticles

Carbon doped titanium oxide (CTiO₂) photocatalyst was successfully synthesized by the sol–gel method. The crystal structure, surface morphology, and optical properties of CTiO₂ have been characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area (S_BET), scanning electron microscope, UV–Vis, X-ray spectroscopy (EDS), Fourier transform infrared and X-ray photoelectron spectroscopy. The photocatalytic degradation of acetaminophen (AMP) in aqueous solution, seawater, and polluted seawater has been investigated by using the synthesized photocatalyst under irradiation of UV and natural sunlight. The effectiveness of CTiO₂ compared to pure TiO₂ toward the photocatalytic removal of AMP was significantly observed. The optimized conditions including catalyst dose, initial concentration of AMP and solution pH were also studied for effective photocatalytic removal. The highest degradation rate was obtained when 2.0 g L^?1 of the catalyst was used at pH 7. The kinetic results revealed that the photocatalytic degradation of AMP using CTiO₂ obeyed a pseudo-first-order reaction kinetics.

     

Catalytic degradation of gaseous benzene by using TiO2/goethite immobilized on palygorskite: Preparation,characterization and mechanism

The nano-TiO₂/goethite/palygorskite catalysts were prepared by sol–gel method. The morphology and structure of the catalysts were analyzed by X-ray diffraction (XRD), UV–Vis reflection spectrometer, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and N₂ adsorption-desorption measurement. The results indicated that the self-made catalysts had excellent catalytic performance on gaseous benzene degradation. In the case of benzene concentration at 30 mg/m³, the degradation efficiency, over TiO₂/goethite/palygorskite composite with mass ratio of 10:5:5, reached 70.4% after 180 min 254 nm UV irradiation. The reaction mechanism and kinetics study showed that palygorskite/goethite/TiO₂ composites photocatalytic degradation benzene was mainly caused by oxidizing property of electron–holes and oxygen synergy effect.     

Preparation,characterization and activity evaluation of p–n junction photocatalyst p-NiO/n-ZnO

In this paper, p–n junction photocatalyst NiO/ZnO was prepared by the sol–gel method using Ni (NO₃)₂ and zinc acetate as the raw materials. The structural and optical properties of the p–n junction photocatalyst NiO/ZnO were characterized by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, UV–Vis diffuse reflection spectrum (DRS) and the fluorescence emission spectra. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic reduction of Cr₂O₇ ²⁻ and photocatalytic oxidation of methyl orange (MO). The results showed that the photocatalytic activity of the p–n junction photocatalyst NiO/ZnO is much higher than that of ZnO on the photocatalytic reduction of Cr₂O₇ ²⁻. However, the photocatalytic activity of the photocatalyst is much lower than that of ZnO on the photocatalytic oxidation of methyl orange. Namely, the p–n junction photocatalyst NiO/ZnO has higher photocatalytic reduction activity, but lower photocatalytic oxidation activity. The heat treatment condition also influences the photocatalytic activity strongly, and the best preparation condition is about 400 °C for 2 h. Effect of the heat treatment condition on the photocatalytic activity of the photocatalyst was also investigated. The mechanisms of influence on the photocatalytic activity were discussed by the p–n junction principle.     

N,B, Si-tridoped mesoporous TiO<Subscript>2</Subscript> with high surface area and excellent visible-light photocatalytic activity

N, B, Si-tridoped mesoporous TiO₂, together with N-doped, N, B-codoped and N, Si-codoped TiO₂, was prepared by a modified sol–gel method. The samples were characterized by wide-angle X-ray diffraction (WAXRD), N₂ adsorption–desorption, transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, UV–visible adsorbance spectra (UV–vis) and X-ray photoelectron spectra (XPS). The N, B, Si-tridoped mesoporous TiO₂ showed small crystallite size, large specific surface area (350 m²/g), uniform pore distribution (3.2 nm) and strong absorption in the visible light region. The photocatalytic activities of the samples were evaluated by the photodegradation of 2,4-dichlorophenol (2,4-DCP) aqueous solution. The N, B, Si-tridoping sample exhibited much higher photocatalytic activity compared with other synthesized photocatalysts. The high activity could be attributed to the strong absorption in the visible light region, large specific surface area, small crystallite size, large amount of surface hydroxyl groups, and mesoporosity.     

Enhanced Photocatalytic Performance of rGO Modulated β-Ga2O3 for Wastewater Treatment

Rapid urbanization has inevitably raised challenges by indirectly adding industry waste to the environment. This problem becomes even more severe when contamination of consumable water is considered. As a leading sector in semiconductor-related research to face such challenges, gallium oxide and its derivatives have shown remarkable performance by exhibiting controlled, recyclable photocatalytic activities. This work demonstrates the enhancement of the photocatalytic performance of β-Ga₂O₃, which is related to the structural and morphological variation induced by rGO wrapping. Firstly, the Ga₂O₃ nanostructures are obtained by calcinating gallium oxide hydroxide (GaOOH), which is synthesized via a simple chemical route. On the other hand, rGO wrapped β-Ga₂O₃ is synthesized using in-situ hydrothermal treatment. In addition to traditional characterizations such as X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, etc., the photocatalytic performance of both pristine and composite systems is studied by time-dependent UV–Vis absorption spectrum for the degradation of different organic toxic pollutants. It is observed that the composite sample exhibited a larger effective surface area and enhanced optical absorption in the UV–Vis range as compared to the pristine gallium oxide sample. Under UV light irradiation, the rGO wrapped β-Ga₂O₃ nanobars can degrade rhodamine B dye entirely within 25 min and exhibit a higher photodegradation rate of 0.1598 min⁻¹ which became 3.5 times higher as compared to that of pure gallium oxide.     

Solar active nano-TiO2 for mineralization of Reactive Red 120 and Trypan Blue: 1st Nano Update

Nano-TiO₂ was synthesized by sol–gel method. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) images, transmission electron microscope (TEM), BET surface area measurement and DRS analysis. The formation of anatase phase nano-TiO₂ was confirmed by XRD measurements and its crystalline size is found to be 15.2 nm. SEM images depict the crystalline nature of prepared TiO₂. The BET surface area of prepared TiO₂ is found to be 86.5 m² g^?1 which is higher than that of commercially available TiO₂–P25. The photocatalytic activity of prepared anatase phase TiO₂ has been tested for the degradation of two azo dyes: Reactive Red 120 (RR 120) and Trypan Blue (TB) using solar light. The photocatalytic activity of nano-TiO₂ is higher than TiO₂–P25 under solar light. The mineralization of dyes has been confirmed by chemical oxygen demand (COD) measurements.     

Enhanced visible‐light‐driven photocatalytic activity of F doped reduced graphene oxide ‐ Bi2WO6 photocatalyst

The reduced graphene oxide‐Bi₂WO₆ (rGO‐BWO) photocatalysts with the different R_F/O values (molar ratio of the F molar mass and the O's molar mass of Bi₂WO₆) had been successfully synthesized via one‐step hydrothermal method. The F‐doped rGO‐BWO samples were characterized by X‐ray diffraction patterns (XRD), field‐emission scanning electron microscopy (FE‐ESEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller surface area (BET), X‐ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectra (DRS). The results indicate that F^? ions had been successfully doped into rGO‐BWO samples. With the increasing of the R_F/O values from 0 to 2%, the evident change of the morphology and the absorption edges of F‐doped rGO‐BWO samples and the photocatalytic activities had been enhanced. Moreover, the photocatalytic activity of F‐doped rGO‐BWO with R_F/O = 0.05 were better than rGO‐BWO and the other F‐doped rGO‐BWO under 500 W Xe lamp light irradiation. The enhanced photocatalytic activity can be attributed to the morphology of the intact microsphere that signify the bigger specific surface area for providing more possible reaction sites for the adsorption–desorption equilibrium of photocatalytic reaction, the introduction of F^? ions that may cause the enhancement of surface acidity and creation of oxygen vacancies under visible light irradiation, the narrower band gap which means needing less energy for the electron hole pair transition.     

Visible light photocatalytic activity and Photoelectrochemical property of Fe-doped TiO<Subscript>2</Subscript> hollow spheres by sol–gel method

Fe-doped TiO₂ hollow spheres (Fe-THs) were synthesized by sol–gel process using carbon spheres as templates. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectrum (DRS), N₂ adsorption–desorption isotherms, Electron paramagnetic resonance (EPR) spectroscopy and Photoluminescence emission spectroscopy (PL). UV–vis spectra showed that Fe³⁺ doping could extend the absorption edge to the visible region. EPR spectra showed that Fe³⁺ was incorporated into the crystal lattice of TiO₂, which could inhibit the recombination of photo-induced electron–hole pairs and improve the photocatalytic activity. The photocatalytic activities of the prepared samples were evaluated for the degradation of dye Reactive Brilliant Red X-3B (C.I. reactive red 2) under visible light irradiation. The results indicated that Fe³⁺ doping sample showed the highest photocatalytic activity with an optimal doping concentration of 0.50 wt%. The recycle ability of the Fe-THs was also investigated. After 5 cycles, the degradation rate was still higher than 90%, decreased by only 6.36% compared to the first cycle. Moreover, in order to characterize the electron-transferring efficiency in the process of photocatalysis reaction, a photocurrent-time spectrum was examined by anodic photocurrent response.     

脉冲沉积制备Cu2O/TiO2纳米管异质结的可见光光催化性能

在用阳极氧化法制备有序排列TiO₂纳米管阵列薄膜的基础上,引入脉冲沉积工艺,成功实现了均匀、弥散分布的Cu₂O纳米颗粒修饰改性TiO₂纳米管阵列,形成Cu₂O/TiO₂ 纳米管异质结复合材料. 利用场发射扫描电镜（FESEM）、场发射透射电镜（FETEM）、X射线衍射（XRD）、X射线光电子能谱（XPS）和紫外-可见漫反射光谱（UV-Vis DRS）对样品进行表征,重点研究了Cu₂O/TiO₂ 纳米管异质结的光电化学特性和对甲基橙（MO）的可见光催化降解性能. 结果表明,Cu₂O纳米颗粒均匀附着在TiO₂纳米管阵列的管口和中部位置,所制备的Cu₂O/TiO₂ 纳米管异质结具有高效的可见光光催化性能;在浓度为0.01 mol·L^-1的CuSO₄溶液中制得的Cu₂O/TiO₂纳米管异质结表现出最好的电化学特性和光催化性能;另外,对Cu₂O纳米颗粒影响光催化活性的机理进行了讨论.     

Photocatalytic performance of Ag doped SnO2 nanoparticles modified with curcumin

Visible light active Ag doped SnO₂ nanoparticles modified with curcumin (Cur–Ag–SnO₂) have been prepared by a combined precipitation and chemical impregnation route. The optical properties, phase structures and morphologies of the as-prepared nanoparticles were characterized using UV–visible diffuse reflectance spectra (UV–vis-DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The surface area was measured by Brunauer. Emmett. Teller (B.E.T) analysis. Compared to bare SnO₂, the surface modified photocatalysts (Ag–SnO₂ and Cur–Ag–SnO₂) showed a red shift in the visible region. The photocatalytic activity was monitored via the degradation of rose bengal (RB) dye and the results revealed that Cur–Ag–SnO₂ shows better photocatalytic activity than that of Ag–SnO₂ and SnO₂. The superior photocatalytic activity of Cur–Ag–SnO₂ could be attributed to the effective electron-hole separation by surface modification. The effect of photocatalyst concentration, initial dye concentration and electron scavenger on the photocatalytic activity was examined in detail. Furthermore, the antifungal activity of the photocatalysts and the reusability of Cur–Ag–SnO₂ were tested.     

A Simple Ni-based Metal–organic Framework as Catalyst for Dye-sensitized Photocatalytic H2 Evolution from Water Reduction

Metal–organic frameworks (MOF) are recently developed coordination porous materials, and their unique structures are very conducive to catalytic reactions. In this paper, p-benzenedicarboxylic acid (PBA)-Ni²⁺ MOF materials (denoted as PBA-Ni-x, where x represents the initial ratio of PBA to Ni²⁺) were synthesized by a hydrothermal method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and N₂ gas adsorption. H₂ gas was produced using the synthesized MOF as a photocatalyst and Eosin Y as a photosensitizer. The dependence of the special surface area and thickness of the nanosheets of Ni-MOF on the initial ratio of PBA to Ni²⁺ (PBA/Ni²⁺) was investigated. The BET surface areas of PBA-Ni-1 PBA-Ni-2 and PBA-Ni-3 are 11.00, 24.61 and 13.04 m² g⁻¹, respectively. And the thicknesses of nanosheets are approximately 600–1000, 200–500 and 300–700 nm. Among the three materials, PBA-Ni-2 has the thinnest sheet-like structure and largest surface area. Thus, it displays the highest H₂ evolution rate of 20.0 μmol h⁻¹. The noble-metal-free hydrogen production system is valuable for the application of MOF materials in photocatalytic water splitting.     

Resonance energy transfer between ZnCdHgSe quantum dots and gold nanorods enhancing photoelectrochemical immunosensing of prostate specific antigen

Gold nanorods (AuNRs) integrated with ZnCdHgSe near-infrared quantum dots (AuNRs-ZnCdHgSe QDs) were successfully synthesized and characterized by transmission electron microscope, X-ray photoelectron spectroscopy, and X-ray diffraction. A glassy carbon electrode was decorated with the aforementioned AuNRs-ZnCdHgSe QDs nanocomposite, which provides a biocompatible interface for the subsequent immobilization of prostate specific antibody (anti-PSA). After being successively treated with glutaraldehyde vapor and bovine serum albumin solution, a photoelectrochemical immunosensing platform based on anti-PSA/AuNRs-ZnCdHgSe QDs/GCE was established. The photocurrent response of ZnCdHgSe QDs was tremendously improved by AuNRs due to the effect of resonance energy transfer which can be deduced from the dependence of the enhanced efficiency on the AuNRs with different length-to-diameter ratios and spectral absorption characteristics. A maximum photocurrent was obtained when the absorption spectrum of AuNRs matched well with the emission spectrum of ZnCdHgSe QDs. A photoelectrochemical immunosensor for prostate specific antigen (PSA) was achieved by monitoring the photocurrent variation. The photocurrent variation before and after being interacted with PSA solution exhibits a good linear relationship with the logarithm of its concentration (logc_PSA) in the range from 1.0 pg mL⁻¹ to 50.0 ng mL⁻¹. The detection limit of this photoelectrochemical immunosensor is able to reach 0.1 pg mL⁻¹ (S/N = 3). Determining PSA in clinical human serum was also demonstrated by using the developed anti-PSA(BSA)/AuNRs-ZnCdHgSe QDs/GCE electrode. The results were comparable with those obtained from an enzyme-linked immunosorbent assay method.     

Enhanced sunlight-driven photocatalytic performance of Bi-doped CdMoO4 benefited from efficient separation of photogenerated charge pairs

In this paper, to further boost the photocatalytic performance of CdMoO₄, Bi³⁺ was successfully doped into CdMoO₄ by a facile microwave hydrothermal method. The Bi-doped CdMoO₄ photocatalysts prepared were characterized by Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), electron spin-resonance (ESR) and surface photovoltage spectroscopy (SPS). The results exhibit that doping Bi³⁺ into CdMoO₄ remarkably boosts the separation rate of photoinduced charge pairs and the specific surface area, decrease the crystal size, narrows the band gap of the CdMoO₄ and induces the binding energy shift of Cd, all these advantageous factors result in the promoted photocatalytic performance of CdMoO₄. Using rhodamine B (RhB) as model toxic pollutant, the photocatalytic activities of the photocatalysts were evaluated under a 500 W Xe lamp irradiation. When the molar ratio of Bi/Cd is 0.2%, Bi-CdMoO₄ prepared displays the best photocatalytic performance, the photocatalytic performance of the 0.2% sample is more than twice of that of the reference CdMoO₄.     

油水自组装制备Ag@AgBr/BiOBr高效可见光催化剂

采用油水自组装法制备Ag@AgBr表面修饰三维花状结构BiOBr复合光催化剂(Ag@AgBr/BiOBr),利用XRD、SEM、TEM、EDX、DRS、XPS、PL及EIS等手段对光催化剂的结构和性能进行了表征,并研究了可见光下降解亚甲基蓝(MB)的催化性能.研究表明:Ag@AgBr粒径约为20nm,均匀分散在花状微球BiOBr表面上;贵金属Ag的表面等离子体效应可显著增强可见光利用率,并有效促进光生电子空穴对的分离,Ag@AgBr(15wt%)/BiOBr光催化剂展现出最优的催化活性,可见光照射30min对MB的降解率将近90%,淬灭实验表明·O₂^-,h⁺和Br⁰均为活性物种.结合理论分析与实验结果提出复合光催化剂的降解机理.     

油水自组装制备Ag@AgBr/BiOBr高效可见光催化剂

采用油水自组装法制备Ag@Ag Br表面修饰三维花状结构Bi OBr复合光催化剂(Ag@Ag Br/Bi OBr),利用XRD、SEM、TEM、EDX、DRS、XPS、PL及EIS等手段对光催化剂的结构和性能进行了表征,并研究了可见光下降解亚甲基蓝(MB)的催化性能。研究表明:Ag@Ag Br粒径约为20 nm,均匀分散在花状微球Bi OBr表面上;贵金属Ag的表面等离子体效应可显著增强可见光利用率,并有效促进光生电子空穴对的分离,Ag@Ag Br(15wt%)/Bi OBr光催化剂展现出最优的催化活性,可见光照射30 min对MB的降解率将近90%,淬灭实验表明·O2-,h+和Br0均为活性物种。结合理论分析与实验结果提出复合光催化剂的降解机理。     

Fe2O3/ZnO/ZnFe2O4 composites for the efficient photocatalytic degradation of organic dyes under visible light

In this study, novel ternary Fe₂O₃/ZnO/ZnFe₂O₄ (ZFO) composites were successfully prepared through a simple hydrothermal reaction with subsequent thermal treatment. The as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, Barrett-Joyner-Halenda (BJH) measurement, and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic degradation of rhodamine B (Rh B) under visible light irradiation indicated that the ZFO composites calcined at 500 °C has the best photocatalytic activity (the photocatalytic degradation efficiency can reach up to 95.7% within 60 min) and can maintain a stable photocatalytic degradation efficiency for at least three cycles. In addition, the photocatalytic activity of ZFO composites toward dye decomposition follows the order cationic Rh B > anionic methyl orange. Finally, using different scavengers, superoxide and hydroxyl radicals were identified as the primary active species during the degradation reaction of Rh B.