One‐pot combustion synthesis and efficient broad spectrum photoactivity of Bi/BiOBr:Yb,Er/C photocatalyst

A highly efficient broad spectrum responsive Bi/BiOBr:Yb,Er/C ternary composite was synthesized by a simple one‐pot combustion method using nitrates and citric acid as raw materials. Experimental results show that Er³⁺/Yb³⁺ were successfully doped into BiOBr lattice, and metallic Bi nanoparticles and carbon species were formed simultaneously. Compared with pure BiOBr and Bi/BiOBr/C, as‐synthesized Bi/BiOBr:Yb,Er/C ternary photocatalyst is highly responsive in the UV‐visible‐NIR range, and possesses the best photodegradation performance for Rhodamine B, phenol, and imidacloprid under visible, NIR, or solar light irradiation, which can be attributed to the synergetic effects of surface plasma resonance of metallic Bi, up‐conversion transition of Er³⁺ and heterojunctions (Bi/BiOBr, Bi/C, and BiOBr/C). Moreover, a plausible mechanism was given, the main active species, and photostability of samples were studied. The solar light photoactivity and influences of pH value and anions (Cl^?, SO₄^2?, CO₃^2?, HCO₃^?, and NO₃^?) were also investigated. This study highlights the advantages of synergetic effects of SPR, up‐conversion and heterojunctions, which provides a useful guide toward the rational design of broad spectrum (UV‐visible‐near infrared) photocatalysts.     

Rapid,simple and low-cost fabrication of BiOBr ultrathin nanocrystals with enhanced visible light photocatalytic activity

BiOBr ultrathin nanocrystals were prepared by a rapid, simple and low-cost route, and characterised by X-ray diffraction, scanning electron microscope, transmission electron microscopy, energy dispersive X-ray, UV–vis diffuse reflectance spectroscopy and electrochemical impedance spectroscopy analyses. The size of the resulting BiOBr ultrathin nanocrystals is about 60–100 nm in width and 15–20 nm in thickness. The photocatalytic activity of the samples was evaluated in terms of the degradation of RhB. Compared with BiOBr three-dimensional microspheres and P₂₅-TiO₂, the BiOBr ultrathin nanocrystals exhibited the best visible-light-induced photocatalytic activity.     

Facile one-pot synthesis of a BiOBr/Bi2WO6 heterojunction with enhanced visible-light photocatalytic activity for tetracycline degradation

Photocatalytic removal of tetracycline (TC) from the wastewater is of great value in the chemical and environmental engineering field. Here, we introduced a facile one-step method for the synthesis of BiOBr/Bi₂WO₆ heterojunctions by using cheap CTAB as the Br source. We showed the possibility of our method to fine-tune the content of BiOBr in the produced BiOBr/Bi₂WO₆ by simply changing the dosage of cetyltrimethylammonium bromide (CTAB), providing a platform for the delicate tuning of the visible-light absorbance ability of the composites. With a suitable heterojunction structure of BiOBr/Bi₂WO₆-0.2, it exhibited an ultrarapid photocatalytic activity towards TC (20 mg·L^-1), with a competitive removal efficiency of 88.1% within 60 min and an ultrahigh removal rate of 0.0349 min^-1. It could also be robustly recycled for at least 5 cycles with slight removal efficiency loss. We demonstrated that this exciting photocatalytic performance was due to the highly decreased recombination of photoinduced electrons and holes on our composites by constructing this heterojunction structure, and the resulting OH and contributed to the effective degradation of TC to CO₂.     

环境友好的BiOBr新型光催化剂制备、表征及其性能研究

采用水热合成的方法通过控制合成条件制备出片状结构的溴化氧铋半导体材料,并通过降解甲基橙染料来考察溴化氧铋半导体材料的光催化特性.应用XRD,SEM,TEM和Uv-vis漫反射光谱来表征BiOBr材料的特性.研究得知,BiOBr是一种间接半导体材料.它的带系能约为2.69eV,且不受合成条件的影响而变化.而BiOBr材料的形貌和结晶度却取决于水热合成的温度和时间.在降解甲基橙染料的过程中这种片状BiOBr显示出很高的先催化活性,特别是在1600℃水热8h后得到的BiOBr材料具有最好的光催化活性.     

Manipulating the charge separation via piezoelectric field and heterojunction to enhance the photoelectrochemical water splitting ability of Bi2WO6/BiOBr photoanode

The unsatisfactory separation efficiency of photogenerated charge is one of the significant problems restricting the application of photoelectrochemical water splitting. Herein, we successfully prepared a Bi₂WO₆/BiOBr nanoplate arrays structure with the heterostructure for efficient piezoelectric photoelectric water splitting. A charge transfer path is formed by constructing a heterojunction to accelerate the spatial separation of photogenerated charges. The Bi₂WO₆/BiOBr shows the better photoelectrochemical performance with high photocurrent density of 0.068 mA/cm² at 1.23 V vs. RHE which is 1.8 times higher than simple Bi₂WO₆. In addition, after the introduction of piezoelectric polarization, the carrier separation efficiency is further enhanced under the synergistic action of the piezoelectric polarization and the heterojunction, and the photocurrent of Bi₂WO₆/BiOBr photoanode is increased to 0.088 mA/cm² at 1.23 V vs. RHE. By comparing the photoelectrocatalytic performance of the samples before and after the introduction of piezoelectric field, it further explains the role of piezoelectric built-in electric field in promoting carrier separation. This work provides a new method to improve the carrier separation efficiency by combining heterojunction and piezoelectric polarization.     

Fabrication of novel ZnO/BiOBr/C-Dots nanocomposites with considerable photocatalytic performances in removal of organic pollutants under visible light

In this study, ternary ZnO/BiOBr/C-Dots photocatalysts were successfully prepared by a simple strategy. Then, their characteristics such as structure, morphology, chemical, optical, textural, and photocatalytic performances were fully investigated. This study demonstrated that the ZnO/BiOBr/C-Dots nanocomposites showed remarkably increased photocatalytic performances compared with the ZnO and ZnO/BiOBr samples. In decolorization of RhB upon visible light, the highest activity was obtained when the volume of C-Dots was 0.25?mL, which was about 39.7 and 2.7?times premier than the ZnO and ZnO/BiOBr photocatalysts, respectively. In the ternary nanocomposites, the increased performance was mainly ascribed to the formed heterojunction between the counterparts, up conversion characteristics of C-Dots, and visible-light harvesting ability of BiOBr. The reactive species trapping experiments proved that O₂^? was the major species involved in the photocatalysis reaction. At last, the ternary nanocomposite displayed remarkable stability for recycling runs.     

Solvothermal synthesis and photocatalytic activity of Al-doped BiOBr microspheres

A series of Al-doped BiOBr microspheres with different Al contents were synthesized via a facile solvothermal method. The as-prepared samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive spectrometry(EDS), X-ray photoelectron spectroscopy(XPS), N₂ adsorption–desorption and UV–visible diffuse reflectance spectroscopy(UV–vis DRS). The photocatalytic activity was evaluated by the photocatalytic degradation of methyl orange in an aqueous solution under visible light irradiation. The results revealed that Al doping could greatly improve photocatalytic performance of BiOBr and different Al contents resulted in different photocatalytic activities. The highest activity was achieved by 4 at%Al-BiOBr. The enhanced photocatalytic activity was attributed to efficient separation of photogenerated electron–hole pairs and large BET surface area.     

Synthesis of mesoporous BiOBr 3D microspheres and their photodecomposition for toluene

In this article, a facile solvothermal method was introduced to synthesize mesoporous BiOBr microspheres with Bi(NO₃)₃ as Bi source. The synthesized catalysts were characterized by XRD, SEM, TEM, XPS, UV-vis, TG-DTA, and N₂-adsorption-desorption, and their photoactivity was evaluated by gaseous toluene both under UV and UV-vis irradiation with Degussa TiO₂ P₂₅ as reference. The prepared BiOBr catalysts were of pure tetragonal phase and its band gap energy was calculated to be about 2.64 eV. Comparing with P₂₅, BiOBr showed promoted photocatalytic activity under UV-vis irradiation, during which more than 90% of toluene was eliminated after 5 h irradiation. Kinetic analysis further demonstrated the enhanced activity of BiOBr under UV-vis irradiation and the reaction rate constant k of BiOBr was nearly 2 times higher than that of P₂₅. The superior activity of BiOBr under UV-vis irradiation can be attributed to its hierarchical structure and suitable band gap energy. Moreover, the reacted intermediates under different light source were identified by GC-MS. Fifteen main intermediates were identified and a tentative pathway of toluene degradation by BiOBr was proposed.     

Pd纳米粒子对BiOBr的光吸收和光催化性能的影响

首先合成高结晶度的BiOBr纳米片,然后利用光化学气相沉积（PCVD）法将不同含量的Pd纳米粒子沉积在BiOBr纳米片上．运用N,一物理吸附．脱附、x射线粉末衍射（XRD）、透射电镜（TEM）、x射线光电子能谱（xIX3）、光致发光（PL）谱、紫外可见漫反射吸收光谱（uV-VisDRS）技术对合成的Pd／BiOBr进行了表征．考察了Pd含量对BiOBr光吸收性能和紫外光（A=254am）、可见光下对染料酸性橙Ⅱ的光催化降解性能的影响．结果表明,沉积Pd对样品的比表面积影响不大,Pd纳米粒子能在一定程度上增强催化剂对可见光的吸收能力,并显著抑制光生电子和空穴的复合．紫外光下,当Pd的质量分数为0．5％时,BiOBr催化降解染料的活性提高到1．6倍,而在可见光下含4％的Pd能使BiOBr表现出最高的催化活性,为纯BiOBr的1．5倍．     

新型BiOBr光催化剂的制备及性能研究

采用水热合成法制备BiOBr可见光催化剂,选择适合的溴源,考察了水热反应温度和时间对制备催化剂的影响。同时采用XRD、BET、Uv-vis紫外-可见光谱等手段对样品进行了表征。研究了BiO-Br可见光照射下的光催化活性。结果表明,在水热反应温度为160℃、水热反应时间为8h的条件下,制备的BiOBr纳米材料具有很好的光催化活性,在降解罗丹明B染料时降解率达93%,BiOBr的晶型结构受反应条件的影响,它的禁带宽度为2.69eV。