| With the development of social economy,environmental pollution and energy shortage have gradually become serious social problems.Solar energy were converted into other types of energy by semiconductor photocatalysis technology,which was directly photocatalytic degradation organic pollutants of waste water or photocatalytic hydrogen production of water splitting,it proposed a green,environmental friendly and low-cost effective method to solve the above two problems.The key to photocatalytic technology is semiconductor photocatalyst.Nevertheless,most single semiconductor materials still have numerous shortcomings.For instance,weak absorption of light,too fast recombination rate of photogenerated electrons and holes,wide band gap and short lifetime of photogenerated carriers,all these factors would influence the absorption,convertion and utiliztion of solar energy converted into chemical energy from semiconductor materials.Therefore,the development of efficient,stable and inexpensive semiconductor composite photocatalysts is a hot spot in the field of environmental field.Black phosphorus(BP),as a new two-dimensional material,has been widely concerned in recent years,and it has been widely used in electronic devices,solar cells,nano-medicine,etc.However,the synthesis of BP and its application in the field of photocatalysis are still in the primary research stage.Base on this,this paper studied the preparation of BP and its photocatalytic performance.The contents and results are as follows:(1)A new reaction system based on chemical vapor transport(CVT)was proposed to synthesized bulk BP crystal with raw materials of red phosphorus(RP),tin(Sn)and iodine(I2).The synthesis of BP crystal and the reaction mechanism in the process of CVT were proved by the experimental characterization.The BP crystal was exfoliated by the method of liquid phase exfoliation to obtain a few layers of BP nano sheets(BPNs)with good morphology,and the results of BPNs layers range from 3.8to 4.1nm.(2)GR/BP hybrid materials were synthesized by one-pot with RP,Sn,I2 and graphene(GR)by CVT method.The GR/BP hybrid material was characterized by X-ray diffraction analysis(XRD).Scanning electron microscope(SEM),transmission electron microscope(TEM),X-ray energy-dispersion spectroscopy(EDS)and Raman spectrum showed that the GR/BP hybrid material was composed of C and P elements and had high purity.The photocatalytic degradation of 2-chlorophenol(2-CP)by GR/BP hybrid materials was studied,and the degradation efficiency reached 87.08%in visible light.The experimental results showed that the degradation efficiency of2-CP by GR/BP hybrid material was 7.29 times as pure BP.Free radical trapping experiment demonstrated that superoxide radical(·O2-)and hydroxyl radical(·OH)played a major role in the degradation of 2-CP.The formation of P-C bond effectively improved the separation efficiency of photogenerated electrons and photogenerated holes,thus increasing the photocatalytic degradation efficiency of 2-CP;and the formation of P-C bond effectively enhanced the stability of BP in photocatalytic reaction.(3)BPNs/Cd S heterostructure were successfully prepared by the simple hydrothermal method.The morphology,crystal structures,light absorption properties and surface physicochemical properties of BPNs/Cd S heterostructure were characterized by SEM,TEM,atomic force electron microscope(AFM),XRD,EDS,Raman spectrum,Ultraviolet-visible diffuse reflection spectroscopy(Uv-vis DRS).The results of characterization experiments showed that the size of BPNs is 3.8 to 4.0nm(about 7 layers)and they were uniformly dispersed on the surface of Cd S,which not only improved the photocatalytic reaction sites and also increased the specific surface area of the material.The visible light photocatalytic activity of BPNs/Cd S heterostructure was studied with Tetrabromobisphenol A(TBBPA)as the target pollutant.The results showed that photocatalytic activity of BPNs/Cd S heterostructure was the highest with 10 wt%BPNs,The efficiency of TBBPA degradation was 95.6%(reaction rate constant Kapp=0.0261 min-1),which was obviously higher than that of pure Cd S(42.4%,Kapp=0.0045 min-1)and commercial Ti O2 P25(18.9%,Kapp=0.0027 min-1).Combine with the experimental results of Mott-Schottky and UV-vis DRS in which the photocatalytic reaction mechanism was studied in detail.BPNs and Cd S form Type?heterojunction,and photogenerated electrons transferred from BPNs conduction band to Cd S conduction band,realizing the separation of photogenerated electron-hole.Photogenerated electrons were transformed to·O2-and·OH to degrade TBBPA.The degradation pathway of TBBPA target pollutants was predicted by theoretical calculation of frontier electron densities(FED)and high performance liquid chromatography-mass spectrometry(HPLC-MS).Then,base on quantitative structure-activity relationship(QSAR)model,the intermediate products with high toxicity in TBBPA degradation process were calculated,the overall toxicity decreased with the photocatalytic degradation process based on luminescent bacteria experiment.(4)BPNs and cyclic titanium-oxo clusters(CTOC)were first synthesized by simple ultrasonic-deposition.The results of SEM,TEM,XRD,EDS and UV-vis DRS experiment showed that BPNs and CTOC structure were successfully compounded;BPNs/CTOC composite had strong absorption in visible light and near infrared region.3 wt%Pt was added as cocatalyst to explore the photocatalytic hydrogen production,the experimental result showed that the efficiency of 20 mg BPNs/CTOC/Pt hydrogen production(methanol was used as the sacrificing agent)in visible light(?>420 nm)and near infrared light(?>780 nm)were 24.3 and 3.78?mol h-1,respectively.In addition,the mechanism of photocatalytic hydrogen production of BPNs/Pt/CTOC composites was revealed.When exposed to visible or near-infrared light,the photogenerated electrons in BPNs were transferred to CTOC to form a typical Type?heterojunction,and then the photogenerated electrons were transferred to Pt and reduced H+generated H2.To sum up,this research based on BP in preparation of nanocomposites established a new two-dimensional material photocatalytic reaction system and examined the different BP-based nanocomposites photocatalytic degradation of pollutants and the hydrogen production.It was revealed the BP photocatalytic reaction mechanism and provided theoretical basis and method technique for the application of BP-based materials in the environmental field.. |
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