title: Visible light driven photoelectrochemical water oxidation on nitrogen-modified TiO2 nanowires.
abstract: We report hydrothermal synthesis of single crystalline TiO(2) nanowire arrays with unprecedented small feature sizes of ~5 nm and lengths up to 4.4 μm on fluorine-doped tin oxide substrates. A substantial amount of nitrogen (up to 1.08 atomic %) can be incorporated into the TiO(2) lattice via nitridation in NH(3) flow at a relatively low temperature (500 °C) because of the small cross-section of the nanowires. The low-energy threshold of the incident photon to current efficiency (IPCE) spectra of N-modified TiO(2) samples is at ~520 nm, corresponding to 2.4 eV. We also report a simple cobalt treatment for improving the photoelectrochemical (PEC) performance of our N-modified TiO(2) nanowire arrays. With the cobalt treatment, the IPCE of N-modified TiO(2) samples in the ultraviolet region is restored to equal or higher values than those of the unmodified TiO(2) samples, and it remains as high as ~18% at 450 nm. We propose that the cobalt treatment enhances PEC performance via two mechanisms: passivating surface states on the N-modified TiO(2) surface and acting as a water oxidation cocatalyst.
authors: Department of Chemical Engineering, Center for Electrochemistry, Texas Materials Institute, Center for Nano and Molecular Science, University of Texas at Austin, 1 University Station C0400 Austin, Texas 78712-0231, USA.
authors: Son
authors: S
authors: Hoang
authors: Siwei
authors: S
authors: Guo
authors: Nathan T
authors: NT
authors: Hahn
authors: Allen J
authors: AJ
authors: Bard
authors: C Buddie
authors: CB
authors: Mullins
mesh_terms: D003460:Crystallization / Q000379:methods*; D004574:Electromagnetic Fields; D008027:Light; D008422:Materials Testing; D008968:Molecular Conformation / Q000528:radiation effects; D049329:Nanostructures / Q000737:chemistry* / Q000528:radiation effects / Q000648:ultrastructure; D009584:Nitrogen / Q000737:chemistry* / Q000528:radiation effects; D010084:Oxidation-Reduction / Q000528:radiation effects; D010316:Particle Size; D011829:Radiation Dosage; D013499:Surface Properties / Q000528:radiation effects; D014025:Titanium / Q000737:chemistry* / Q000528:radiation effects; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; C009495:titanium dioxide; D014025:Titanium; D009584:Nitrogen