Page - 132 - in Photovoltaic Materials and Electronic Devices

p-nheterojunctions. Moreover, theheterojunctionsofp-BiOI/n-TiO2 NFscouldbe well recycledbysedimentationwithoutdecreasingtheirphotocatalyticactivities. 2. ResultsandDiscussion 2.1. Morphologies Figure 1 shows the scanning electron microscopy (SEM) images of different samples. It can be seen that TiO2 nanofibers with a diameter about 250 nm are relativesmoothwithoutsecondarystructures. AfterSILARprocess,asobservedin Figure 1b–d, the TiO2 nanofibers become rough and are decorated with ultrathin BiOI nanosheets and remain as one-dimension nanofibers structure. When the cycles of SILAR process increase to 30 for the BiOI/TiO2-C30, the amount of the BiOInanosheets increasessignificantlycomparedwith thoseofBiOI/TiO2-C10and BiOI/TiO2-C20. These results suggest that the heterojunctions of p-BiOI/n-TiO2 NFs mayhaveahigherspecificsurfacearea,whichisgoodforthephotocatalyticreactions. Materials  2016,  9,  90  3  of  12    Figure  1.  (a)  SEM  images  of  TiO2  nanofibers;  (b)  BiOI/TiO2‐C10;  (c)  BiOI/TiO2‐C20;  and    (d)  BiOI/TiO2‐C30  at  low  magnification  and  high  magnification  (insets).  Figure 1. (a)SEMimagesofTiO2 anofibers; (b)BiOI/TiO2-C10; (c)BiOI/TiO2-C20; and(d)BiOI/TiO2-C30at lowmagnificationandhighmagnification(insets). Figure2a,bshowsthetypicalTEMimagesofBiOI/TiO2-C30. It canbeobserved thatnumerousBiOInanosheetsarerandomlydistributedonTiO2 nanofibers. The BiOI nanosheets are very thin, which coincides with the results of SEM observations. 132