Fabrication of BiVO_4:Effect of Structure and Morphology on Photocatalytic Activity and Its Methylene Blue Decomposition Mechanism

BiVO_4 photocatalysts were synthesized by a surfactant free hydrothermal method without any further treatments,and characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),ultraviolet-visible diffuse reflectance spectroscopy(UV-vis DRS),Raman spectroscopy,and Brunauer-Emmett-Teller(BET) surface area techniques.The photocatalytic activity was evaluated for the degradation of the methylene blue(MB) under visible light irradiation.Seen from the structural and morphological characterization,it is stated that the obtained samples present monoclinic phase,and the pH value has significant influence on the morphologies.The enhanced photocatalytic performance was associated with its crystallinity,unique morphology,band gap energy,BET specific surface area,surface charge and adsorption capacity.The recycle experiments results show that the BiVO_4 photocatalysts have excellent photo-stability,and we deduced a possible mechanism by examining the effects of the active species involved in the photocatalytic process for MB photocatalytic degradation.     

Fabrication of BiVO<Subscript>4</Subscript>: Effect of structure and morphology on photocatalytic activity and its methylene blue decomposition mechanism

BiVO₄ photocatalysts were synthesized by a surfactant free hydrothermal method without any further treatments, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), Raman spectroscopy, and Brunauer-Emmett-Teller (BET) surface area techniques. The photocatalytic activity was evaluated for the degradation of the methylene blue (MB) under visible light irradiation. Seen from the structural and morphological characterization, it is stated that the obtained samples present monoclinic phase, and the pH value has significant influence on the morphologies. The enhanced photocatalytic performance was associated with its crystallinity, unique morphology, band gap energy, BET specific surface area, surface charge and adsorption capacity. The recycle experiments results show that the BiVO₄ photocatalysts have excellent photo-stability, and we deduced a possible mechanism by examining the effects of the active species involved in the photocatalytic process for MB photocatalytic degradation.     

p-n异质结TiO_2/NiO光催化剂的制备及其性能研究

采用溶胶凝胶和浸渍煅烧相结合的方法,制备出了具有p-n异质结结构的球形二氧化钛表面负载氧化镍颗粒的复合光催化剂.利用XRD、TEM、UV-Vis和PL等方法对催化剂的晶相组成、微观结构、吸光性能和光致发光性能等进行了表征.结果表明氧化镍晶粒与二氧化钛晶粒紧密接触形成p-n异质结.氧化镍颗粒的负载使复合光催化剂的吸收带边发生了明显的红移,并进入了可见光区.形成的p-n异质结促进了二氧化钛光生电子和空穴的分离,从而降低了其本征发光光强度.通过在可见光条件下对亚甲基蓝的降解研究了其光催化性能,结果表明,氧化镍颗粒的负载使二氧化钛的光催化效果在可见光区有了显著地提高,并在一定范围内随着氧化镍含量的增加光催化效果也随之提高.     

Synthesis and characterization of W-doped TiO2 supported by hybrid carbon nanomaterials of multi-walled carbon nanotubes and C60 fullerene by a hydrothermal method

W-doped TiO2 supported by hybrid carbon nanomaterials of multi-walled carbon nanotubes and C60 fullerene was synthesized by a simple hydrothermal method. The material displayed high visible light photocatalytic activity. X-ray diffraction, field emission transmission electron microscopy, ultra violet/visible light absorption and photoluminescence spectroscopy were used to characterize the material as photocatalyst. Photocatalytic activity on the degradation of Rhodamine B dye in an aqueous solution under ultraviolet light and visible light irradiation was also studied. The experimental results indicated that the photocatalytic activity of the material was much higher than that of pure TiO2 or Degussa P25 TiO2.     

Synthesis of novel CaCO_3/Ag_2CO_3/Ag I/Ag plasmonic photocatalyst with enhanced visible light photocatalytic activity.

In this work, novel Ca CO3/Ag2CO3/Ag I/Ag plasmonic photocatalysts were successfully synthesized by a two-step in situ ion exchange process and their photocatalytic properties were studied. The morphology, crystal structure and optical properties of the as-prepared Ca CO3/Ag2CO3/Ag I/Ag nanocomposites were characterized by transmission electron microscopy(TEM), XRay diffraction(XRD), and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity of the obtained nanocomposites was evaluated by the photodegradation of methyl orange(MO) under visible light irradiation. It was found that the as-prepared Ca CO3/Ag2CO3/Ag I/Ag plasmonic photocatalyst exhibits high visible light photocatalytic activity. With an optimized composition, MO dye can be decomposed by more than 94% within 15 min under visible light irradiation. Moreover, the photocatalytic stability could be greatly improved upon the addition of Na2CO3 into the photocatalytic system. From the proposed photocatalytic mechanism, the strong surface plasmon resonance effect of Ag nanoparticles and the efficient separation of photogenerated electrons and holes can effectively enhance the photocatalytic performance of the Ca CO3/Ag2CO3/ Ag I/Ag composites.     

A facile synthesis of Ag Modified ZnO nanocrystals with enhanced photocatalytic activity

Ag modified ZnO (Ag/ZnO) nanocrystals were prepared by a facile and low temperature wet chemical method. The phase structures, morphologies, and optical properties of the as-prepared samples were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), the Brumauer-Emmett-Teller (BET) surface area, UV-vis diffuse reflectance spectroscopy and photoluminescence (PL) spectra, respectively. The photocatalytic performance of Ag/ZnO with diffent Ag contents was measured with the degradation of methyl orange (MO) at room temperature under UV light irradiation. The experimental results indicated that the well-crystalline ZnO nanopaticles with a size of ca. 4.5 nm exhibited a high photocatalytic activity for the degradation of MO with the apparent rate constant (k) of 1.57 ×10-2 min-1, and the photocatalytic activities of ZnO were further enhanced by modification with silver. When the Ag loading was 3mol%, Ag/ZnO showed the highest photocatalytic acitivity with a k value of 5.452×10-2 min-1, which is 3.5 and 2.5 time more than that of ZnO and commercial P25, respectively.     

Meso-macroporous Fe-doped Cu O: Synthesis,characterization, and structurally enhanced adsorption and visible-light photocatalytic activity

The meso-macroporous Fe-doped Cu O was prepared by a simple hydrothermal method combined with post-annealing. The samples were characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), Brunauer-Emmett-Teller N2 adsorption-desorption analyses and UV-vis diffuses reflectance spectroscopy. The Fe-doped Cu O sample shows higher adsorption capacity and photocatalytic activity for xanthate degradation than pure Cu O under visible light irradiation. In addition, the adsorption process is found to fit Langmuir isotherms and pseudo-second-order kinetics. The the first order kinetic Langmuir Hinshelwood model was used to study the reaction kinetics of photocatalytic degradation, and the apparent rate constant( k) was calculated. The value of k for Fe-doped Cu O is 1.5 times that of pure Cu O. The higher photocatalytic activity of Fe-doped Cu O is attributed to higher specific surface area together with stronger visible light absorption.     

石墨烯／二氧化钛复合光催化剂的制备及可见光催化性能研究

以钛酸正丁酯为钛源,采用一种简单的原位水解技术制备了石墨烯／二氧化钛复合光催化剂．通过XRD、SEM、TEM、Raman、PL和UV-vis光谱仪等分析手段对产物进行了表征,并测试了该复合光催化剂在可见光区对染料罗丹明B的光催化降解性能．实验结果表明：制备的复合光催化剂主晶相为锐钛矿型二氧化钛,石墨烯表面富集的二氧化钛颗粒尺寸约为10-20nm左右,均匀弥散、形成一层致密的氧化钛膜层．样品降解罗丹明B测试结果表明,石墨烯与二氧化钛的复合,一方面使得二氧化钛光催化剂在可见光区的吸收大大增强,另外,石墨烯的存在能够促进二氧化钛半导体中电子和空穴的有效分离,并且在一定程度上提高了污染物在半导体表面的富集效率,从而使石墨烯／二氧化钛复合光催化剂对降解罗丹明B表现出良好的光催化活性．     

Co2+离子掺杂对TiO2结构与光催化活性的影响

论文采用溶胶-凝胶法制备Co2+掺杂的TiO2纳米粉末,以苯酚为目标污染物研究了Co-TiO2在不同的光源（紫外、可见）下的光催化活性,并利用XRD、EFSEM、UV-DRS和XPS等手段分析Co-TiO2结构与光催化活性的关系。结果表明,一部分Co2+离子成功进入TiO2晶格,有助于金红石相向锐钛矿相转变;另一部分Co2+离子在催化剂表面生成Co3O4,可与TiO2形成p-n异质结,两种结构变化均增强了光催化活性,且催化剂光谱吸收范围拓展至可见光区域。当Co2+掺杂量为1.0%,焙烧温度为773K时,Co-TiO2比表面积约为28.4m2/g,锐钛矿含量达到70.6%,光催化活性最好。2小时内,在紫外和可见光下,Co-TiO2对苯酚的降解率分别为97.7%和52.3%,均优于纯TiO2。     

Photocatalytic degradation of rhodamine B dye with MWCNT/TiO<Subscript>2</Subscript>/C<Subscript>60</Subscript> composites by a hydrothermal method

Multi-walled carbon nanotube (MWCNT)/TiO2/C60 composite catalysts were prepared by hydrothermal method. TiO2 was deposited on the MWCNT surface. Their photocatalytic activities for degradation of Rhodamine B dye were studied. X-ray diffraction, field emission transmission electron microscopy, ultraviolet-visible light absorption spectrum and photoluminescence spectrum were carried out to characterize the composite catalysts. The results indicated that MWCNTs and C60 could greatly enhance the photocatalytic activity of TiO2.     

Visible Light-induced Cr-doped SrTiO_3-g-C_3N_4 Composite for Improved Photocatalytic Performance

Novel visible light-induced Cr-doped Sr Ti O3-g-C3N4 composite photocatalysts were synthesized by introducing polymeric g-C3N4. The composite photocatalyst was characterized by X-ray diffraction(XRD), high-resolution transmission electron microscopy(HRTEM), Fourier transform infrared(FT-IR) spectroscopy, UV-vis diffuse reflection spectroscopy, photoluminescence(PL) spectroscopy and BET surface area measurements. The photocatalytic oxidation ability of the novel composite photocatalyst was evaluated using methyl orange(MO) as a target pollutant. The photocatalysts exhibited a significantly enhanced photocatalytic performance in degrading MO. The optimal g-C3N4 content for the photodegradation activity of the composite photocatalysts was determined. The as-prepared composite photocatalyst exhibits an improved photocatalytic activity due to enhancement of photo-generated electron-hole separation at the interface.     

燃烧法制备铁酸镍复合氧化物及光催化研究

抗坏血酸为燃烧剂,燃烧法制备铁酸镍复合氧化物。XRD表征分析确定硝酸铁和硝酸镍的最佳物质 的量比,紫外-可见光谱仪分析得到铁酸镍复合氧化物的吸光性能,电镜分析出复合物的形貌。以亚甲基蓝(0.01 g/L,100mL)为降解目标,铁酸镍复合氧化物为催化剂,双氧水为氧化剂进行复合物的光催化研究。结果表明,催化 剂用量、酸度、双氧水用量、光催化时间等条件对光催化都有着重要影响。光催化最佳实验条件为催化剂质量 20mg、pH=6、双氧水体积为6mL。实验结果表明,硝酸镍、硝酸铁和抗坏血酸物质的量比为1∶2∶1时,复合氧化 物在紫外和可见光下均有光催化效果;硝酸镍、硝酸铁和抗坏血酸物质的量比为2∶1∶1和1∶3∶1时,复合氧化物 在紫外光下有光催化效果。     

Hydrothermal Synthesis of Zn_2SnO_4/Few-Layer Boron Nitride Nanosheets Hybrids as a Visible-Light-Driven Photocatalyst

Zn_2SnO_4/few-layer boron nitride nanosheets(FBNNS) hybrids were synthesized via a one-step hydrothermal method. The structures, morphology, optical properties, electron transformation and separation of the as-prepared products were characterized by X-ray diffraction, transmission electrical microscopy, UV-vis diffuse reflectance spectroscopy and electrochemical impedance spectroscopy, respectively. Rhodamine B was used to evaluate the photocatalytic activities of the as-prepared samples under visible light illumination. The photocatalytic mechanism was also explored. Experimental results showed that the degradation efficiency of rhodamine B was firstly increased and then decreased with increasing the usage amount of FBNNS. When it was 9 wt% based on the weight of Zn_2 SnO_4, the degradation efficiency of the as-prepared Zn_2 SnO_4/FBNNS-9 wt% composites reached to the maximum of 97.5 % in 180 min, which was higher than 39.2 % of pure Zn_2 SnO_4. Moreover, the holes played mainly active roles in photocatalytic reaction process. In addition, the as-prepared hybrids could enhance the separation efficiency of photoexcited carriers compared to pure Zn_2 SnO_4.     

Preparation, characterization and photocatalytic activity of N-doped TiO_2 nanocrystals

N-doped TiO_2 nanocrystals were prepared using titanium alkoxide as precipitant with different proportional materials. The products were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy, and UV-vis diffuse reflectance spectra. It is confirmed experimentally that the photocatalytic activity of N-doped TiO_2 is much higher than that of Degussa P25, when used for the degradation of crystal violet.The degradation kinetics follows an apparent first-order reaction,which is consistent with a generally observed Langmuir-Hinshelwood mechanism. The doping of TiO_2 with nitrogen significantly increases the absorption in the region of visible light. The energy of the band gap of N-doped TiO_2 is 2.92 eV. The better performante of N-doped TiO_2 can be explained by the fact that it is also excited with longer-wavelength light.     

Highly Efficient Removal of Organic Dyes by Novel As-synthesized AgBr/montmorillonite Composite

A facile deposition method has been developed for large-scale synthesis of visible-light-driven AgBr/montmorillonite composite catalyst for the first time. The as-synthesized samples were characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR), transmission electron microscopy(TEM), UV-vis diffuse reflectance spectroscopy(UV-vis DRS) and Brunauer-Emmett-Teller(BET) surface area analysis, respectively. Through the combined action of adsorption and photodegradation, the as-prepared AgBr/montmorillonite composite exhibited a higher removal efficiency for rhodamine B(RhB) than that of Na-montmorillonite and AgBr. For the methyl orange(MO) removal, the AgBr/montmorillonite composite possessed a superior photocatalytic performance compared with Namontmorillonite and AgBr. The enhanced photocatalytic activity of AgBr/montmorillonite composite can be attributed to the effective separation of the electron-hole pairs. In AgBr/montmorillonite suspension, the superoxide radicals are the main reactive oxygen species for dye degradation under visible light illumination.     

MxTiNbO5对甲烷中甲硫醇吸附与光催化性能研究

采用水热法合成层状KTiNbO5,通过离子交换获得Mn0.5TiNbO5和Ni0.5TiNbO5。利用X-射线衍射（XRD）、紫外-可见漫反射光谱（UV—vis-DRS）、扫描电镜（SEM）、高分辨透射电镜（HRTEM）等对催化剂进行表征。采用红外光谱技术考察了催化剂对甲烷气中甲硫醇吸附与光催化氧化性能。结果表明：在相同层板组成下,层间金属离子不同,对光谱的响应及对有机硫化物的吸附与光催化氧化能力不同。经Mn^2＋和Ni^2＋对KTiNbO5离子交换后,对光谱吸收由紫外区移向可见光区;动态条件下,KTiNbO5和Mn0.5TiNbO5虽对甲烷气中的甲硫醇吸附很弱,但Mn0.15TiNbO5在自然光与紫外光下对硫醇有催化氧化活性;而Ni0．5TiNbO5对甲烷气中的甲硫醇不仅具有良好的吸附活性,且在自然光与紫外光辐射下均显示了良好的光催化氧化活性。     

立方体形Ag3PO4可见光光催化剂的制备及其性能研究

以AgNO3、Na2HPO4和NH3.H2O为主要原料,利用银氨辅助法成功制备出了在可见光照射下具有高的光催化活性的立方体形Ag3PO4光催化剂.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FTIR)和紫外可见光谱仪(UV-Vis)等分别对Ag3PO4样品的晶相组成、微观形貌和吸光度等进行了表征,并且考察了该光催化剂在模拟太阳光照射下对罗丹明溶液的光催化降解效果.结果表明,所制备出的立方体形Ag3PO4晶体是由6个{100}晶面包裹而成,与球形的Ag3PO4样品相比,立方体形的Ag3PO4样品表现出更优越的光催化活性,这主要是由于由高活性的{100}晶面主导的立方体形Ag3PO4样品对可见光有更高的吸收能力、更高的电子与空穴分离效率,以及更多的光催化活性中心.     

In situ construction of BiVO4(-)cellulose fibers@CDs(-)polyvinyl alcohol composites for tetracycline photocatalytic degradation

Non-biodegradable and toxic photocatalysts pose as secondary threats to the environmental security. In this work, non-toxic biocomposites were prepared using natural bamboo cellulose fibers(CF), polyvinyl alcohols(PVAs), BiVO_4, and carbon dots(CDs) from biomaterials. Thereafter, their optical properties, chemical characterizations, and photocatalytic performances were evaluated. The novel BiVO_4(-)CF@CDs(-)PVA composites were prepared via the combined implementation of in situ and impregnation methods. The optical properties revealed that the CDs and fibers increased the range and intensity of light absorption. The PVAs were used as the shield and dispersant to enhance stability because they have numerous chemical groups.In view of the various possible paths of electron migration, the enhanced photocatalytic activity of BiVO_4(-)CF@CDs(-)PVA composites for tetracycline degradation was observed under visible light illumination. The origins of the structure, morphology,and optical mechanism in the enhancement of the photocatalytic ability of BiVO_4(-)CF@CDs(-)PVA composites were discussed and demonstrated.     

Synthesis of zinc oxide nanoparticles with good photocatalytic activities under stabilization of bovine serum albumin

Zinc oxide nanoparticles were synthesized using bovine serum albumin as stabilizers through a facile one-pot strategy in aqueous media. The morphology and crystal phase of the zinc oxide nanoparticles were determined by transmission electron microscopy, X-ray diffractograms, and Fourier transform infrared spectroscopy. The synthesized ZnO nanoparticles exhibited strong absorption and photoluminescence properties in the visible wavelength region based on the fluorescence and UV-visible spectroscopy. Based on the results, the zinc oxide nanoparticles could effectively degrade the organic dyes through the mediation of the hydroxyl radical under visible light irradiation. Furthermore, the zinc oxide nanoparticles show good recycling stability during the photocatalytic experiments. These results suggested that the as-prepared zinc oxide nanoparticles might be used as a potential photocatalyst to efficiently treat the organic pollutants.     

NH2-UiO-66/BiOBr/Bi2S3光催化剂的合成及其光催化性能

采用溶剂热法制备NH₂-UiO-66/BiOBr/Bi₂S₃（UBB）三元复合光催化剂,利用X射线衍射（XRD）、扫描电镜（SEM）表征该催化剂的晶体结构和微观形貌,为了评价其光催化活性及稳定性,在可见光下催化降解有色染料亚甲基蓝（MB,20 mg/L）和罗丹明B（RhB,20 mg/L）。结果表明:NH₂-UiO-66的含量为2%时,UBB的光催化活性最好,对MB的降解率在60 min内达到93.5%,对RhB的降解率在30 min内达到98.3%;MB和RhB初始浓度提高到100 mg/L时,光催化降解率仍保持在70%以上;4次循环试验后,UBB的催化活性无明显降低。本文采用紫外可见漫反射光谱（UV-vis DRS）、荧光光谱（PL）和阻抗（EIS）的3种表征方法,分析UBB光催化性能变化的原因,并结合莫特-肖特基（M-S）曲线、活性物质捕捉实验结果,提出适用于UBB三元体系的双Z型电子转移机制。