Local structures of cobalt in Co-doped TiO 2 by synchrotron x-ray absorption near edge structures

Abstract

ABSTRACT The local structures of cobalt in Co-doped TiO 2 were studied by combining K -edge x-ray absorption near edge structures (XANES) measurements with first-principles calculations. The Co/TiO 2 samples were prepared by (1) sol-gel and (2) co-precipitation methods. To identify the local structure around Co, the measured spectra are compared against the spectra measured from Co 3 O 4 , CoO and Co foil standard samples as well as first principles XANES based on several atomic models. For the sample prepared by the co-precipitation method, Co atoms clearly form a separated Co 3 O 4 phase because the XANES spectrum is almost identical to that of Co 3 O 4 . For the sample prepared by the sol-gel method, the spectrum does not look like a spectrum of any of the standards. The possible local structures of Co in the sol-gel prepared sample are discussed. Our work illustrated that XANES is a powerful technique that can be used to probe the local structures of minority atoms even if the standard x-ray diffraction techniques failed.