Mechanisms for adsorption, dissociation and diffusion of hydrogen in hydrogen permeation barrier of α-Al2O3: The role of crystal orientation

• Published in: International journal of hydrogen energy Vol. 39; no. 1; pp. 610 - 619
• Main Authors: Zhang, Guikai, Dou, Sanping, Lu, Yongjie, Shi, Yan, Lai, Xinchun, Wang, Xiaolin
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier 02.01.2014
• Subjects: Adsorption; Alternative fuels. Production and utilization; Applied sciences; Barriers; Binding energy; Diffusion; Diffusion barriers; Energy; Exact sciences and technology; Fuels; Hydrogen; Hydrogen-based energy; Migration; Surface chemistry; Hydrogen diffusion; Crystal orientation; Hydrogen; α-Al; Hydrogen adsorption; Hydrogen permeation barrier; O
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2013.10.063

The mechanisms of adsorption of hydrogen on alpha -Al2O3(1-102) surface and of its diffusion in bulk are investigated, using first principles thermodynamics and kinetics, and compared with similar results obtained for the diffusion of hydrogen on alpha -Al2O3(0001) surface. Because of the different oxygen environments on both surfaces, the H binding energies on the (1-102) surface are 0.3-1.2 eV smaller than in the (0001) surface. The H2 binding energies on (1-102) and (0001) surfaces are resembled. We have identified four main mechanisms, leading to dissociation of H2, H migration on the surface, H diffusion into and inside the bulk. Equilibrium constant and activation barrier show that H2 dissociation is the most favorable process and significant diffusion of H into the bulk can occur more readily from the (1-102) surface compared to the (0001) surface. Based on the hydrogen interaction with alpha -Al2O3(1-102) surface, a mechanism of alpha -Al2O3 suppressing H-permeation is identified.