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MBE Growth and Properties of N-doped TiO2 for Enhanced Visible Light Absorption and Water Splitting


EMSL Project ID
19393

Abstract

Development of new energy sources is a major need for the 21st century. Hydrogen has considerable potential as an alternative fuel. Fujishima and coworkers discovery in 1969 that water could be photocatalytically split on TiO2 electrodes has motivated research toward development of visible light active photocatalysts. While TiO2 absorbs little of the solar spectrum, cation-doping red-shifts the TiO2 absorption spectrum into the visible, but without apparent activity for water splitting. Promising results have emerged recently on a new class of visible-light active TiO2 photocatalysts doped with anions (C, N, S). Emerging research effort has approached anion-doped TiO2 photocatalysis from a phenomenological perspective, placing emphasis on catalyst preparation and performance evaluation, and not on developing a fundamental understanding at the molecular-level. As such, there is a specific opportunity for basic science to provide a solid foundation of understanding of how doping influences the visible-light photocatalytic properties of TiO2 and a general need for a better understanding of the heterogeneous photocatalytic water splitting reaction. At the heart of any fundamental investigation of these phenomena are well-defined model materials. To this end, we propose to investigate the epitaxial growth and properties of N-doped TiO2 films in both the anatase and rutile polymorphs. We will use oxygen plasma assisted molecular beam epitaxy to prepare single-crystal films of N-doped rutile on rutile TiO2(110), (110) and (101) as well as -Al2O3(0001), and N-doped anatase on SrTiO3(001) and LaAlO3(001). We will characterize the material properties of these films using reflection high energy electron diffraction and x-ray/ultraviolet photoemission spectroscopies in situ, and then ex-situ high-resolution x-ray diffraction, Rutherford backscattering and transmission electron microscopy at PNNL, along with near-edge and extended x-ray absorption fine structure at the National Synchrotron Light Source and the Advanced Light Source. We will determine how the structural and compositional affects of N doping map onto the electronic, optical and photochemical properties.

Project Details

Project type
Large-Scale EMSL Research
Start Date
2006-07-21
End Date
2009-09-30
Status
Closed

Team

Principal Investigator

Scott Chambers
Institution
Pacific Northwest National Laboratory

Team Members

Andrew Mangham
Institution
Pacific Northwest National Laboratory

Dong Kim
Institution
Pacific Northwest National Laboratory

Takeo Ohsawa
Institution
Pacific Northwest National Laboratory

Steve Heald
Institution
Argonne National Laboratory

Sau Ha Cheung
Institution
Pacific Northwest National Laboratory

Michael Henderson
Institution
Pacific Northwest National Laboratory

Ponnusamy Nachimuthu
Institution
Environmental Molecular Sciences Laboratory

Vaithiyalingam Shutthanandan
Institution
Environmental Molecular Sciences Laboratory

Chongmin Wang
Institution
Environmental Molecular Sciences Laboratory

Jose Rodriguez
Institution
Brookhaven National Laboratory

Charles Fadley
Institution
Lawrence Berkeley National Laboratory

Related Publications

"Crystallographic dependence of visible-light photoactivity in epitaxial TiO2-xNx anatase and rutile." Physical Review B 79(8): 085401. Petrik, N. G. and G. A. Kimmel (2009).