Properties of Methane and Carbon Adsorbed at the Interface between Molten NaBr and Ni(111)

Maryam Tarazkar*, Horia Metiu, Henrik Høgh Kristoffersen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Electronicstructure calculations and constant temperature ab initiomolecular dynamics simulations were used to study the molten NaBr–Ni(111)interface. The presence of molten NaBr has a pronounced effect on the Ni(111) surface. For instance, the Na+ and Br– ion concentrations are increased at the interface and Bader charge analysis shows that negative charge is transferred from Br– ions at the interface to the Ni(111) surface. The molten NaBr also destabilizes dissociated methane (*CH + 3H*) adsorbed at the NaBr–Ni(111)interface compared to dissociated methane adsorbed on Ni(111) without NaBr. Carbon dimers (*C2) at the NaBr–Ni(111) interface are found to be kinetically and thermodynamically unstable and dissociate into carbon atoms. Furthermore, carbon atoms initially placed at the NaBr–Ni(111) interface or on the bare Ni(111) surface quickly diffuse into the Ni(111) slab. The molten NaBr increases the stability of atomic carbon in the subsurface region. Nickel nanoparticles would be excellent catalysts for methane pyrolysis if they did not rapidly coke. One goal of this study was therefore to investigate whether a molten salt would hinder or remove coke from the Ni(111) surface.Molten NaBr may help keep the Ni(111) surface clean of carbon and catalytically active by favoring subsurface carbon. It is however uncertain whether subsurface carbon is desirable, as it has been reported that dissolved carbon precipitates out of the nickel particles as carbon whiskers that block the catalyst bed.
Original languageEnglish
JournalJournal of Physical Chemistry C
Volume125
Pages (from-to)3980−3987
ISSN1932-7447
DOIs
Publication statusPublished - 2021

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