Abstract: In order to improve the photocatalytic efficiency of visible light,highly crystalline Co-doped ZnO powders with different Co2+ doping concentrations (1 mol%-5 mol%) are prepared by a co-precipitation method using ZnCl2,Co(NO3)2·6H2O and NaOH as reactants.The morphology,crystal structure and optical property of the Co-doped ZnO samples are characterized by X-Ray diffraction,scanning electron microscopy and UV-Vis absorption spectroscopy.It is indicated that the resultant ZnO powders have an absorption band in the whole visible light region.ZnO powders with a Co-doping concentration of 3 mol% exhibits the highest photocatalytic activity with its first-order rate constant of 1.739 6×10-3 min-1.The band structures and defect level of ZnO are calculated based on first principle.It is found that the sharp absorption peak at 650 nm can be assigned to the transitions of ZnO electron from its valence band to impurity level or from impurity level to the conduction band.The experimental results show that Co-doped ZnO may help visible light increase photocatalytic efficiency.
[1] 牛凤兴,陈晨,陈钰,等.水热法制备Co/ZnO及其光催化降解邻苯二酚的研究[J].现代化工,2018,8:21-. [2] 万燕,魏任星,卢挺,等.二氧化钛多相光催化降解有机污染物影响因素研究进展[J].现代化工,2018,38(5):53-56. [3] Tong H,Ouyang S,Bi Y,et al.Nano-photocatalytic materials:Possibilities and challenges[J].Advanced Materials,2012,24(2):229-251. [4] Rehman S,Ullah R,Butt A M,et al.Strategies of making TiO2 and ZnO visible light active[J].Journal of Hazardous Materials,2009,170(2-3):560-569. [5] Hui A,Ma J,Liu J,et al.Morphological evolution of Fe doped sea urchin-shaped ZnO nanoparticles with enhanced photocatalytic activity[J].Journal of Alloys and Compounds,2017,696:639-647. [6] Zhai B G,Ma Q,Yang L,et al.Synthesis of morphology-tunable ZnO nanostructures via the composite hydroxide mediated approach for photocatalytic applications[J].Materials Research Express,2016,3(10):105045. [7] Thennarasu G,Sivasamy A.Metal ion doped semiconductor metal oxide nanosphere particles prepared by soft chemical method and its visible light photocatalytic activity in degradation of phenol[J].Powder Technology,2013,250:1-12. [8] Kuriakose S,Satpati B,Mohapatra S.Enhanced photocatalytic activity of Co doped ZnO nanodisks and nanorods prepared by a facile wet chemical method[J].Physical Chemistry Chemical Physics,2014,16(25):12741-12749. [9] Qiu X,Li G,Sun X,et al.Doping effects of Co2+ ions on ZnO nanorods and their photocatalytic properties[J].Nanotechnology,2008,19(21):215703. [10] Lu Y,Lin Y,Xie T,et al.Enhancement of visible-light-driven photoresponse of Mn/ZnO system:Photogenerated charge transfer properties and photocatalytic activity[J].Nanoscale,2012,4(20):6393-6400. [11] Xiao S,Zhao L,Lian J.Enhanced photocatalytic performance of supported Fe doped ZnO nanorod arrays prepared by wet chemical method[J].Catalysis Letters,2014,144(2):347-354. [12] Wu C,Shen L,Yu H,et al.Solvothermal synthesis of Cu-doped ZnO nanowires with visible light-driven photocatalytic activity[J].Materials Letters,2012,74:236-238. [13] Yıldırım Ö A,Unalan H E,Durucan C.Highly efficient room temperature synthesis of silver-doped zinc oxide (ZnO:Ag) nanoparticles:Structural,optical,and photocatalytic properties[J].Journal of the American Ceramic Society,2013,96(3):766-773. [14] Xu C,Cao L,Su G,et al.Preparation,characterization and photocatalytic activity of Co-doped ZnO powders[J].Journal of Alloys and Compounds,2010,497(1-2):373-376. [15] Zhao J,Wang L,Yan X,et al.Structure and photocatalytic activity of Ni-doped ZnO nanorods[J].Materials Research Bulletin,2011,46(8):1207-1210. [16] Huang Y M,Ma Q L,Zhai B G.Core-shell Zn/ZnO structures with improved photocatalytic properties synthesized by aqueous solution method[J].Functional Materials Letters,2013,6(6):1350058. [17] Ma Q,Xiong R,Zhai B,et al.Core-shelled Zn/ZnO microspheres synthesised by ultrasonic irradiation for photocatalytic applications[J].Micro & Nano Letters,2013,8(9):491-495. [18] Zhai B,Ma Q,Huang Y M.Instability of the characteristic emissions of dopant Tb in ZnO hexagonal pyramids[J].Journal of Electronic Materials,2017,46(2):947-954. [19] Zhai B G,Yang L,Ma Q L,et al.Visible light driven photocatalytic activity of Fe-doped ZnO nanocrystals[J].Functional Materials Letters,2017,10(2):1750002. [20] Zhai B,Liu D,He Y,et al.Tuning the photoluminescence of Eu2+ and Eu3+ co-doped SrSO4 through post annealing technique[J].Journal of Luminescence,2018,194:485-493. [21] Zhai B,Huang Y M.Green photoluminescence and afterglow of Tb-doped SrAl2O4[J].Journal of Materials Science,2017,52(4):1813-1822. [22] Archer T,Pemmaraju C D,Sanvito S.Magnetic interaction of Co ions near the (1010) ZnO surface[J].New Journal of Physics,2010,12(8):083061. [23] Xu M,Zhao H,Ostrikov K,et al.Effect of doping with Co and/or Cu on electronic structure and optical properties of ZnO[J].Journal of Applied Physics,2009,105(4):043708. [24] He R,Hocking R K,Tsuzuki T.Co-doped ZnO nanopowders:Location of cobalt and reduction in photocatalytic activity[J].Materials Chemistry and Physics,2012,132(2-3):1035-1040. [25] Goktas A,Aslan F,Tumbul A,et al.Tuning of structural,optical and dielectric constants by various transition metal doping in ZnO:TM (TM=Mn,Co,Fe) nanostructured thin films:A comparative study[J].Ceramics International,2017,43(1):704-713. [26] Ba-Abbad M M,Takriff M S,Benamor A,et al.Synthesis and characterisation of Co2+-incorporated ZnO nanoparticles prepared through a sol-gel method[J].Advanced Powder Technology,2016,27(6):2439-2447. [27] Shi S,Yang Y,Xu J,et al.Structural,optical and magnetic properties of Co-doped ZnO nanorods prepared by hydrothermal method[J].Journal of Alloys and Compounds,2013,576:59-65. [28] Zhang F,Cui H,Zhang W.Identifying properties of Co-doped ZnO nanowires from first-principles calculations[J].Vacuum,2015,119:131-135. [29] Badaeva E,Feng Y,Gamelin D R,et al.Investigation of pure and Co2+-doped ZnO quantum dot electronic structures using the density functional theory:Choosing the right functional[J].New Journal of Physics,2008,10(5):055013. [30] Sanyal B,Grånäs O,Knut R,et al.Electronic structure of Co doped ZnO:Theory and experiment[J].Journal of Applied Physics,2008,103(7):07D130. [31] Zhang J M,Gao D,Xu K W.The structural,electronic and magnetic properties of the 3d TM (V,Cr,Mn,Fe,Co,Ni and Cu) doped ZnO nanotubes:A first-principles study[J].Science China Physics,Mechanics and Astronomy,2012,55(3):428-435.