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The possibility of in situ doping during electrochemical anodization of titania nanotube arrays is demonstrated and the mechanism and variations in structural and electronic characteristics of the nanotube arrays as after doping is systematically explored. In the presence of strontium as the dopant, bulk analysis shows strontium mainly incorporated into the lattice of TiO2. Surface analysis, however, reveals phase segregation of SrO in the TiO2 matrix at high Sr doping levels. The near edge X‐ray absorption fine structure (NEXAFS) spectroscopy analysis reveals that Sr2+ doping only alters the Ti and O ions interaction in the TiO2 lattice on the surface with no effect on their individual charge states. An in‐depth understanding of the dopant incorporation mechanism and distribution into TiO2 nanotube arrays is achieved using high resolution transmission electron microscopy (HRTEM) and the high angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) coupled with the electron energy loss spectroscopy (EELS) measurements on the surface and bulk of the nanotubes. Upon their use to photoelectrochemically split water, the Sr‐doped TiO2 nanotube film shows incident photon conversion efficiencies (IPCE) as high as 65%. The enhanced light activity in conjunction with the ordered one‐dimensional morphology makes the fabricated films promising candidates for water photoelectrolysis.

We demonstrate the vertical self-organized growth of thin-film SrTiO 3 (STO) nanotube arrays (NTAs) on SiO 2 substrate. The surface morphology and crystal orientation of the grains at the exterior wall of the backbone TiO 2 nanotube arrays were found to play an important role in the growth rate as well as the final morphology of the STO NTAs. A formation mechanism is proposed that involves nucleation of SrTiO 3 nanocubes through a semitopochemical route followed by a self-assembly process resulting from the Ostwald-ripening-assisted oriented attachment of SrTiO 3 nanocubes. It was shown that under appropriate reaction kinetics the nanotube architecture of the overall template can be maintained to form STO NTAs. The application of this novel platform enables a controlled and efficient mass fabrication of STO NTAs on widely used inexpensive silicon substrates, which can potentially lead to full integration with electronics in the near future.

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