Net-like titanate nanowire films can be grown on Ti substrates by non-hydrothermal treatment of Ti foils in alkali-H_2O_2 aqueous solutions with a low alkali concentration of 2 M at 60-80. The growth mechanism of such...Net-like titanate nanowire films can be grown on Ti substrates by non-hydrothermal treatment of Ti foils in alkali-H_2O_2 aqueous solutions with a low alkali concentration of 2 M at 60-80. The growth mechanism of such films has been investigated by identifying the role of both H_2O_2 and alkali in the nanowire formation and capturing the film morphology at early growth stages. It is found that the presence of H_2O_2 is necessary for the nanowire growth, and sufficient amount of H_2O_2 is needed to produce well-shaped nanowires.The nanowire growth is also strongly dependant on the alkali used, and nanowire films are formed only when metal hydroxides which can react with TiO_2 to form layer-structured titanates are chosen. Our results have also revealed that the heterogeneous deposition of titanate on Ti substrate results in the growth of titanate sheets, and the nanowire formation is via a splitting process by which each titanate sheet gradually evolves into nanowire thin layer. Based on the experimental results, a detailed mechanism is proposed for the growth of titanate nanowire films in alkali-H_2O_2 aqueous solutions at low temperature.展开更多
Net-like titanium oxide or H-titanate nanowire films were grown on Ti substrates in 2 mol/L NaOH solutions at 80 ℃ via anodization method or chemical oxidation followed by proton-exchange. The microstructure, thermal...Net-like titanium oxide or H-titanate nanowire films were grown on Ti substrates in 2 mol/L NaOH solutions at 80 ℃ via anodization method or chemical oxidation followed by proton-exchange. The microstructure, thermal stability and photoelectrochemical property of two types of films were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and photocurrent measurement. It is found that the anodic film mainly consists of a 500-nm-thick nenowire layer whereas the film formed by chemical oxidization is made up of two layers： a nanowire layer （nearly 1 tim in thickness） and an underlying non- nanowire layer （at least 1 μm in thickness）. In both two cases, the as-formed nanowires are partly crystallized. Thermal stability investigation reveals that the net-like structure of the anodic nanowire film almost keeps unchanged at a temperature less than 400℃ but is totally destroyed when being calcinated at 600 ℃. In contrast, the nanowire layer formed by chemical method is stable even after being calcinated at 600 ℃. Our results also show that the uncalcinated or calcinated anodic films are much more photoactive than the corresponding films prepared by chemical oxidization. The difference in photoelectrochemical property of two types of films is discussed based on their microstructures.展开更多
基金supported by the Natural Science Foundation of Zhejiang Province (No. LY12B07011)
文摘Net-like titanate nanowire films can be grown on Ti substrates by non-hydrothermal treatment of Ti foils in alkali-H_2O_2 aqueous solutions with a low alkali concentration of 2 M at 60-80. The growth mechanism of such films has been investigated by identifying the role of both H_2O_2 and alkali in the nanowire formation and capturing the film morphology at early growth stages. It is found that the presence of H_2O_2 is necessary for the nanowire growth, and sufficient amount of H_2O_2 is needed to produce well-shaped nanowires.The nanowire growth is also strongly dependant on the alkali used, and nanowire films are formed only when metal hydroxides which can react with TiO_2 to form layer-structured titanates are chosen. Our results have also revealed that the heterogeneous deposition of titanate on Ti substrate results in the growth of titanate sheets, and the nanowire formation is via a splitting process by which each titanate sheet gradually evolves into nanowire thin layer. Based on the experimental results, a detailed mechanism is proposed for the growth of titanate nanowire films in alkali-H_2O_2 aqueous solutions at low temperature.
基金supported by the Natural Science Foundation of Zhejiang Province,China(No.LY12B07011)
文摘Net-like titanium oxide or H-titanate nanowire films were grown on Ti substrates in 2 mol/L NaOH solutions at 80 ℃ via anodization method or chemical oxidation followed by proton-exchange. The microstructure, thermal stability and photoelectrochemical property of two types of films were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and photocurrent measurement. It is found that the anodic film mainly consists of a 500-nm-thick nenowire layer whereas the film formed by chemical oxidization is made up of two layers： a nanowire layer （nearly 1 tim in thickness） and an underlying non- nanowire layer （at least 1 μm in thickness）. In both two cases, the as-formed nanowires are partly crystallized. Thermal stability investigation reveals that the net-like structure of the anodic nanowire film almost keeps unchanged at a temperature less than 400℃ but is totally destroyed when being calcinated at 600 ℃. In contrast, the nanowire layer formed by chemical method is stable even after being calcinated at 600 ℃. Our results also show that the uncalcinated or calcinated anodic films are much more photoactive than the corresponding films prepared by chemical oxidization. The difference in photoelectrochemical property of two types of films is discussed based on their microstructures.
