Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 119, Issue 4, Pages 2222-2230Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jp511080q
Keywords
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Funding
- NSERC
- CRC
- CFI
- OIT
- NRC
- CIHR
- University of Saskatchewan
- CLS Graduate Student Travel Support Program
- Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]
- National Natural Science Foundation of China [U1232102]
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The electronic structure and optical properties of Pd-modified TiO2 nanotubes (NTs) with a vertically aligned nanotubular structure grown by a two-step electrochemical anodization method have been studied using X-ray spectroscopy. X-ray absorption near-edge structure (XANES) at the Ti L-3,L-2- and O K-edges was used to investigate the TiO2 NTs before and after Pd modification. It was found that Pd nanoparticles (NPs) are uniformly coated on the NT surface. The Pd L-3-edge of the deposited Pd NPs shows a more intense whiteline and a blue shift for the Pd L-3-edge absorption threshold relative to Pd metal, indicating charge depletion from the Pd 4d orbital as a result NP formation. The lattice of Pd is slightly contracted upon NP formation, although it remains fcc as revealed by extended X-ray absorption fine structure (EXAFS) analysis at the Pd K-edge. X-ray-excited optical luminescence (XEOL) together with XANES with element and site specificity was used to study the optical luminescence from TiO2 NTs. It was found that the defect-originated XEOL intensity dropped noticeably in the Pd NP-coated NTs, suggesting a Pd NP-TiO2-interaction-mediated reduction in the radiative recombination of electrons and holes. Further evidence is provided by Ti 2p resonant inelastic X-ray scattering (RIXS), in which no low-energy loss features (d-d transitions) were observed. The implications of these results are discussed.
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