Spontaneous dissociation of H_2 and high energy barrier of H invasion on W doped Al_2O_3(0001) surface

摘要

In view of the wide use of tungsten in fusion experimental devices and the importance of hydrogen isotopes permeation, here we studied the adsorption, dissociation, diffusion and invasion behavior of hydrogen on W doped a-Al2O3 (0001) surface. Based on the firstprinciple approaches, we found the W substitution for a top surface Al atom is the most energetically favorable. H2 molecule prefers to be adsorbed on the surface W and spontaneously dissociates into two H anions. Near the W defects, H atoms favor to be adsorbed at the W and Al sites rather than O sites on the surface, and within the subsurface layer H can only bond to W stably. As a result, H migration to subsurface should occur around W with an energy barrier as large as 4.22 eV which is much larger than the 1.91 eV around the O atom on undoped a-Al2O3 (0001) surface. These findings suggest that W surface doping is beneficial to a-Al2O3 as tritium permeation barrier. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.