XAFS Study of the Al K-Edge in NaAlH4

Abstract

Al K-edge (1561.1 eV) XANES and EXAFS spectra of unoxidized NaAlH4, a hydrogen storage material, have been recorded in He atmosphere in a special in situ low-energy cell. The XANES spectrum of NaAlH4 is reported and compared to that of oxidized NaAlH4, thus illustrating the power of XANES spectroscopy as a quick qualitative check of the NaAlH4. For the EXAFS data, reliable fits of the Al K-edge spectra could be obtained when all scattering contributions, i.e., Al-H, Al-Na, and Al-Al, were incorporated into the fit. The hydrogen atoms made a significant contribution to the Al K-edge EXAFS signal of NaAlH4, which stresses the importance of hydrogen scattering when analyzing EXAFS data of this metal hydride.