title: Water-photolysis properties of micron-length highly-ordered titania nanotube-arrays.
abstract: We report the water photoelectrolysis and photoelectrochemical properties of the titania nanotube arrays as a function of nanotube crystallinity, length (up to 6.4 microm), and pore size. Most noteworthy of our results, under 320-400 nm illumination (98 mW/cm2) the titania nanotube-array photoanodes (area 1 cm2), pore size 110 nm, wall thickness 20 nm, and 6 microm length, generate hydrogen by water photoelectrolysis at a rate of 7.6 mL/hr, with a photoconversion efficiency of 12.25%. The energy-time normalized hydrogen evolution rate is 80 mL/hrW, the largest reported hydrogen photoelectrolysis generation rate for any material system by a factor of four. The highly-ordered nanotubular architecture appears to allow for superior charge separation and charge transport, with a calculated quantum efficiency of over 80% for incident photons with energies larger than the titania bandgap.
authors.affiliation: Department of Electrical Engineering, Department of Materials Science and Engineering, and The Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Oomman K
authors.initials: OK
authors.lastname: Varghese
authors.forename: Maggie
authors.initials: M
authors.lastname: Paulose
authors.forename: Karthik
authors.initials: K
authors.lastname: Shankar
authors.forename: Gopal K
authors.initials: GK
authors.lastname: Mor
authors.forename: Craig A
authors.initials: CA
authors.lastname: Grimes
mesh_terms: D004563:Electrochemistry / Q000379:methods; D006859:Hydrogen; D008027:Light; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D037742:Nanotubes, Carbon; D010777:Photochemistry / Q000379:methods; D010782:Photolysis; D011199:Potentiometry; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D014867:Water; D014961:X-Ray Diffraction
chemical_list: D037742:Nanotubes, Carbon; D014867:Water; C009495:titanium dioxide; D006859:Hydrogen; D014025:Titanium