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Kinetics and Mechanisms for the Adsorption, Dissociation, and Diffusion of Hydrogen in Ni and Ni/YSZ Slabs: A DFT Study
journal contribution
posted on 2016-02-21, 16:02 authored by Meng Hsiung Weng, Hsin-Tsung Chen, Yao-Chun Wang, Shin-Pon Ju, Jee-Gong Chang, M. C. LinThe adsorption, dissociation, and diffusion of hydrogen
in Ni(100)
and Ni(100)/YSZ(100) slabs with two different interfaces (Ni/cation
and Ni/O interface) have been studied by the density functional theory
(DFT) with the Perdew–Wang functional. The H2 molecule
is found to preferentially absorb on a Top (T) site with
side-on configuration on the Ni(100) surface, while the H-atom is
strongly bound at a fcc Hollow (H) site. The barrier
for the H2 dissociation on both surfaces is calculated
to be only ∼0.1 eV. The potential energy pathways of H diffusion
on pure Ni and Ni/YSZ with the two different interfaces are studied.
Our calculated results show that the H-atom diffusion occurs via surface
path rather than the bulk path. For the bulk path in Ni/YSZ, H-atom
migration can occur more readily at the Ni/cation interface compared
to the Ni/O interface. The existence of vacancy in the interface region
is found to improve the mobility of H-atoms at the interface of Ni/YSZ
slab. The rate constants for hydrogen dissociation and diffusion in
pure Ni and Ni/YSZ are predicted.