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Effect of hydrogen gas impurities on the hydrogen dissociation on iron surface
Author(s) -
Staykov Aleksandar,
Yamabe Junichiro,
Somerday Brian P.
Publication year - 2014
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.24633
Subject(s) - dissociation (chemistry) , hydrogen , chemistry , adsorption , oxygen , chemisorption , catalysis , inorganic chemistry , hydrogen embrittlement , photochemistry , organic chemistry
A small addition of oxygen to hydrogen gas is known to mitigate the hydrogen embrittlement (HE) of steels. As atomic hydrogen dissolution in steels is responsible for embrittlement, catalysis of molecular hydrogen dissociation by the steel surface is an essential step in the embrittlement process. The most probable role of oxygen in mitigating HE is to inhibit the reactions between molecular hydrogen and the steel surface. To elucidate the mechanism of such surface reaction of hydrogen with the steel in the presence of oxygen, hydrogen, and oxygen adsorption, dissociation, and coadsorption on the Fe(100) surface were investigated using density functional theory. The results show that traces of O 2 would successfully compete with H 2 for surface adsorption sites due to the grater attractive force acting on the O 2 molecule compared to H 2 . The H 2 dissociation would be hindered on iron surfaces with predissociated oxygen. Prompted by the notable results for H 2 + O 2 , other practical systems were considered, that is, H 2 + CO and CH 4 . Calculations were performed for the CO chemisorption and H 2 dissociation on iron surface with predissociated CO, as well as, CH 4 surface dissociation. The results indicate that CO inhibition of H 2 dissociation proceeds via similar mechanism to O 2 induced inhibition, whereas CH 4 traces in the H 2 gas have no effect on H 2 dissociation. © 2014 Wiley Periodicals, Inc.