MoS_2/BiOI复合光催化剂制备及其光催化氧化还原性能
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摘要
通过两步法合成花状MoS_2/BiOI复合光催化剂,采用X射线衍射(XRD)、扫描电镜(SEM)、紫外可见漫反射(UVVis)、光电子能谱(XPS)等方法对合成的样品进行了表征,对其可能的形成机制进行探究,通过电化学表征计算出BiOI与MoS_2的价带与导带位置,显示复合材料形成了1型异质结.同时以罗丹明B(RhB)与含Cr6+溶液作为目标污染物测试光催化剂的氧化还原性能,相比于BiOI和MoS_2单体,MoS_2/BiOI复合光催化剂表现出更强的光催化氧化与还原能力,其中以质量分数为2%的MoS_2与BiOI复合光催化剂效果最佳,可见光照20 min后RhB降解率达到98.92%,80 min后Cr6+溶液光催化还原率可达到97.87%,较纯BiOI分别提高了1.79倍与3.85倍,且经过4次重复利用后仍具有较高的光催化活性.光催化降解Rh B过程中空穴(h+)与超氧自由基(·O-2)作为主要活性物种,其中空穴影响更为显著.
Based on a two-step approach,a flower-like MoS_2/BiOI composite with a heterojunction has been successfully fabricated.X-ray diffraction(XRD),scanning electron microscopy(SEM),UV-Vis diffuse reflectance spectroscopy(DRS),and X-ray photoelectron spectroscopy(XPS) were used to characterize the prepared MoS_2/BiOI.The formation mechanism of this heterostructure was investigated.The valence band(VB) and conduction band(CB) of the MoS_2/BiOI heterojunction have been calculated based on electrochemical characterization,implying the formation of a type I band alignment.The photodegradation of Rhodamine B(Rh B) and Cr6 +were used to assess photocatalytic reduction and oxidation activities.The results show that the MoS_2/BiOI composite structures perform much better than pristine MoS_2 and BiOI.Among the composites with various MoS_2 contents,2% MoS_2/BiOI exhibits the best efficiency with respect to the degradation of Rh B.After irradiation for 20 minutes,the degradation rate of Rh B was 98.82%,which is1.79 times higher than that using pure BiOI.After irradiation for 80 minutes,the removal of Cr6 +was 97.87%,which is 3.85 times higher than that using pure BiOI.Holes and ·O-2 are the main reactive species during the photocatalytic process of Rh B degradation;holes play the leading role.
Based on a two-step approach,a flower-like MoS_2/BiOI composite with a heterojunction has been successfully fabricated.X-ray diffraction(XRD),scanning electron microscopy(SEM),UV-Vis diffuse reflectance spectroscopy(DRS),and X-ray photoelectron spectroscopy(XPS) were used to characterize the prepared MoS_2/BiOI.The formation mechanism of this heterostructure was investigated.The valence band(VB) and conduction band(CB) of the MoS_2/BiOI heterojunction have been calculated based on electrochemical characterization,implying the formation of a type I band alignment.The photodegradation of Rhodamine B(Rh B) and Cr6 +were used to assess photocatalytic reduction and oxidation activities.The results show that the MoS_2/BiOI composite structures perform much better than pristine MoS_2 and BiOI.Among the composites with various MoS_2 contents,2% MoS_2/BiOI exhibits the best efficiency with respect to the degradation of Rh B.After irradiation for 20 minutes,the degradation rate of Rh B was 98.82%,which is1.79 times higher than that using pure BiOI.After irradiation for 80 minutes,the removal of Cr6 +was 97.87%,which is 3.85 times higher than that using pure BiOI.Holes and ·O-2 are the main reactive species during the photocatalytic process of Rh B degradation;holes play the leading role.
引文
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[2]黄建辉,林文婷,谢丽燕,等.石墨相氮化碳-碘氧化铋层状异质结的构建及其光催化杀菌性能[J].环境科学,2017,38(9):3979-3986.Huang J H,Lin W T,Xie L Y,et al.Construction of graphitic carbon nitride-bismuth oxyiodide layered heterostructures and their photocatalytic antibacterial performance[J].Environmental Science,2017,38(9):3979-3986.
[3]鲍玥,周旻昀,邹骏华,等.C3N4/BiOBr复合可见光催化剂的性能及其作用机制[J].环境科学,2017,38(5):2182-2190.Bao Y,Zhou M J,Zou J H,et al.Performance and mechanism study of visible light-driven C3N4/BiOBr composite photocatalyst[J].Environmental Science,2017,38(5):2182-2190.
[4]Zhao J L,Lv XW,Wang X X,et al.Fabrication of Bi OX(X=Cl,Br,and I)nanosheeted films by anodization and their photocatalytic properties[J].Materials Letters,2015,158:40-44.
[5]Meng X C,Zhang Z S.New insight into BiOX(X=Cl,Br,and I)hierarchical microspheres in photocatalysis[J].Materials Letters,2018,225:152-156.
[6]Yang Y,Zhang C,Cui L,et al.BiOX(X?=-Cl,Br,I)photocatalytic nanomaterials:applications for fuels and environmental management[J].Advances in Colloid and Interface Science,2018,254:76-93.
[7]Wang C X,Lin H H,Xu Z Z,et al.One-step hydrothermal synthesis of flowerlike Mo S2/CdS heterostructures for enhanced visible-light photocatalytic activities[J].Royal Society of Chemistry Advances,2015,5(20):15621-15626.
[8]Thangavel S,Thangavel S,Raghavan N,et al.Efficient visiblelight photocatalytic and enhanced photocorrosion inhibition of Ag2WO4decorated Mo S2nanosheets[J].Journal of Physics and Chemistry of Solids,2017,110:266-273.
[9]Wang H S,Qiao X L,Chen J G,et al.Mechanisms of PVP in the preparation of silver nanoparticles[J].Materials Chemistry and Physics,2005,94(2-3):449-453.
[10]Nemamcha A,Moumeni H,Rehspringer J L.PVP Protective mechanism of palladium nanoparticles obtained by sonochemical process[J].Physics Procedia,2009,2(3):713-717.
[11]Zhang B C,Yu H Y,Sun D B.Shape-controlled synthesis and formation mechanism of cobalt nanopowders by a PVP-assisted method[J].Materials Science Forum,2010,654-656:1186-1189.
[12]Crespo-Quesada M,Yarulin A,Jin M S,et al.Structure sensitivity of alkynol hydrogenation on shape-and size-controlled palladium nanocrystals:which sites are most active and selective?[J].Journal of the American Chemical Society,2011,133(32):12787-12794.
[13]Kaur R,Tripathi S K.Study of conductivity switching mechanism of CdSe/PVP nanocomposite for memory device application[J].Microelectronic Engineering,2015,133:59-65.
[14]Fu J,Tian Y L,Chang B B,et al.BiOBr-carbon nitride heterojunctions:synthesis,enhanced activity and photocatalytic mechanism[J].Journal of Materials Chemistry,2012,22(39):21159-21166.
[15]Bai X,Wan J,Jia J,et al.Simultaneous photocatalytic removal of Cr(Ⅵ)and RhB over 2D Mo S2/Red phosphorus heterostructure under visible light irradiation[J].Materials Letters,2018,222:187-191.
[16]周宇,徐玉福,胡献国.铵离子插层Mo S2的制备与表征[J].应用化学,2008,25(1):5-8.Zhou Y,Xu Y F,Hu X G.Preparation and characterization of molybdenum disulfide with NH+4interlayer[J].Chinese Journal of Applied Chemistry,2008,25(1):5-8.
[17]Mc Shane C M,Choi K S.Photocurrent enhancement of n-type Cu2O electrodes achieved by controlling dendritic branching growth[J].Journal of the American Chemical Society,2009,131(7):2561-2569.
[18]Xu H,Yan J,Xu Y G,et al.Novel visible-light-driven Ag X/graphite-like C3N4(X=Br,I)hybrid materials with synergistic photocatalytic activity[J].Applied Catalysis B:Environmental,2013,129:182-193.
[19]Jiang D L,Li J,Xing C S,et al.Two-dimensional CaIn2S4/gC3N4heterojunction nanocomposite with enhanced visible-light photocatalytic activities:Interfacial engineering and mechanism insight[J].ACS Applied Materials&Interfaces,2015,7(34):19234-19242.
[20]Xia J X,Yin S,Li H M,et al.Improved visible light photocatalytic activity of sphere-like BiOBr hollow and porous structures synthesized via a reactable ionic liquid[J].Dalton Transactions,2011,40(19):5249-5258.
[21]Wongkalasin P,Chavadej S,Sreethawong T.Photocatalytic degradation of mixed azo dyes in aqueous wastewater using mesoporous-assembled Ti O2nanocrystal synthesized by a modified sol-gel process[J].Colloids and Surfaces A:Physicochemical and Engineering Aspects,2011,384(1-3):519-528.
[22]李荣荣,姜恒,宫红,等.g-C3N4的制备及其对不同染料光催化降解性能研究[J].应用化工,2016,45(9):1700-1704.Li R R,Jang H,Gong H,et al.Simple synthesis of g-C3N4catalyst for the photocatalytic degradation of different dyes[J].Applied Chemical Industry,2016,45(9):1700-1704.
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[25]Yu C L,Fan C F,Yu J C,et al.Preparation of bismuth oxyiodides and oxides and their photooxidation characteristic under visible/UV light irradiation[J].Materials Research Bulletin,2011,46(1):140-146.
[26]Cheng H F,Huang B B,Dai Y,et al.One-step synthesis of the nanostructured Ag I/BiOI composites with highly enhanced visible-light photocatalytic performances[J].Langmuir,2010,26(9):6618-6624.
[27]Xu M,Han L,Dong S J.Facile fabrication of highly efficient gC3N4/Ag2O heterostructured photocatalysts with enhanced visible-light photocatalytic activity[J].ACS Applied Materials&Interfaces,2013,5(23):12533-12540.
[28]李莉莉,陈翠柏,兰华春,等.g-C3N4协同光催化还原Cr(Ⅵ)及氧化磺基水杨酸[J].环境科学,2017,38(4):1483-1489.Li L L,Chen C B,Lan H C,et al.Simultaneous photocatalytic reduction of Cr(Ⅵ)and oxidation of SSA by carbon nitride[J].Environmental Science,2017,38(4):1483-1489.