AVS 59th Annual International Symposium and Exhibition
    Energy Frontiers Focus Topic Friday Sessions
       Session EN+SS-FrM

Paper EN+SS-FrM5
Narrowing of Band Gap in 1D Arrays of TiO2 Nanoparticles for Photocatalysis: Studies using X-ray Spectroscopies with In Situ Water Exposure and Heating

Friday, November 2, 2012, 9:40 am, Room 15

Session: Photocatalysis and Solar Fuels
Presenter: Y. Liu, University of California Irvine
Authors: Y. Liu, University of California Irvine
J. Taing, University of California Irvine
C.C. Chen, SLAC National Accelerator Lab
A. Sorini, Lawrence Livermore National Lab
M.H. Cheng, University of California Irvine
H. Bluhm, Lawrence Berkeley National Lab
Z. Liu, Lawrence Berkeley National Lab
T. Devereaux, SLAC National Accelerator Lab
J.C. Hemminger, University of California Irvine
Correspondent: Click to Email
Titanium(IV) oxide (TiO2) has a wide range of applications in energy science and acts as a stable support for photocatalysts and sensitizers. Utilizing ambient pressure synchrotron x-ray photoelectron and absorption spectroscopies, we explore the properties of TiO2 thin films and ordered linear arrays of TiO2 nanoparticles under in situ water vapor exposure and heating. Our nondestructive depth profiles (obtained by varying the photoelectron kinetic energy) of electronic and surface structures, combined with density-functional theory calculations, indicate an enhancement of the density of states (DOS) near the Fermi level due to surface Ti3+ and oxygen vacancies. Introducing water on the interface suppresses this DOS enhancement. The Ti L-edge and O K-edge absorption spectra, in combination with atomic multiplet calculations, provide information on crystal field effects and multiplet interactions, helping to determine the phases of the TiO2 particles. Our in situ studies suggest that isolated TiO2 nanoparticles may enhance solar absorption efficiency, and the TiO2 band gap can be tuned reversibly under water exposure and heating.