title: Photoelectrochemical water splitting using dense and aligned TiO2 nanorod arrays.
abstract: Dense and aligned TiO2 nanorod arrays are fabricated using oblique-angle deposition on indium tin oxide (ITO) conducting substrates. The TiO2 nanorods are measured to be 800-1100 nm in length and 45-400 nm in width with an anatase crystal phase. Coverage of the ITO is extremely high with 25 x 10(6) mm(-2) of the TiO2 nanorods. The first use of these dense TiO2 nanorod arrays as working electrodes in photoelectrochemical (PEC) cells used for the generation of hydrogen by water splitting is demonstrated. A number of experimental techniques including UV/Vis absorption spectroscopy, X-ray diffraction, high-resolution scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoelectrochemistry are used to characterize their structural, optical, and electronic properties. Both UV/Vis and incident-photon-to-current-efficiency measurements show their photoresponse in the visible is limited but with a marked increase around approximately 400 nm. Mott-Schottky measurements give a flat-band potential (V(FB)) of +0.20 V, a carrier density of 4.5 x 10(17) cm(-3), and a space-charge layer of 99 nm. Overall water splitting is observed with an applied overpotential at 1.0 V (versus Ag/AgCl) with a photo-to-hydrogen efficiency of 0.1%. The results suggest that these dense and aligned one-dimensional TiO2 nanostructures are promising for hydrogen generation from water splitting based on PEC cells.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, 1156 High St., Santa Cruz, CA 95064, USA.
authors.forename: Abraham
authors.initials: A
authors.lastname: Wolcott
authors.forename: Wilson A
authors.initials: WA
authors.lastname: Smith
authors.forename: Tevye R
authors.initials: TR
authors.lastname: Kuykendall
authors.forename: Yiping
authors.initials: Y
authors.lastname: Zhao
authors.forename: Jin Z
authors.initials: JZ
authors.lastname: Zhang
mesh_terms: D055664:Electrochemical Techniques; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D043942:Nanotubes / Q000737:chemistry*; D055668:Photochemical Processes; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D014867:Water; C009495:titanium dioxide; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D014025:Titanium