A mechanism of ultraviolet activation of the alpha-AlH3 decomposition

作者：Gabis I E^*; Baraban A P; Kuznetsov V G; Elets D I; Dobrotvorskii M A; Voyt A P

来源：International Journal of Hydrogen Energy, 2014, 39(28): 15844-15850.

DOI：10.1016/j.ijhydene.2014.07.154

• Alane
• Decomposition kinetics
• UV activation
• Electronic structure
• Hydrogen vacancies
• Luminescence

We investigated the mechanism of activation of alpha-AlH3 powder decomposition by irradiation with ultraviolet (UV) light using barometry, photoluminescence (PL), cathode luminescence (CL) and X-ray diffraction (XRD) methods. Exposing the samples under a mercury lamp through the filters we have shown that only the line, corresponding to the energy of 4.88 eV, leads to activation, whereas the spectral lines of lower energy are ineffective. XRD shows that after continued UV activation the aluminum clusters with metallic properties are formed on the surface of the AlH3 powder particles at room temperature. The analysis of results of performed calculations of the absorption spectrum of the perfect crystal alpha-AlH3 using DFT method showed that hydrogen vacancies are involved in activation by UV light. Studying of dynamics of CL and PL spectra at different UV expositions permitted to suggest the following mechanism of activation. Absorption of a photon implies that vacancy captures an electron from a neighboring hydrogen atom. Hydrogen atom then can leave its regular position in the lattice and form a new vacancy next to the first. Clustering of vacancies occurs. Continued UV activation is accompanied by merging of vacancies, which deprives the aluminum atoms of hydrogen bonds connecting them. Thus the aluminum clusters with metallic properties are formed.

• 出版日期2014-9-23