Abstract
A dimer model Pd2 was established to study the adsorption of CHx (x = 1–4) and CH4 dehydrogenation, as well as syngas formation using density functional theory (DFT) at the atomic level. Meanwhile, insight into understanding the role of the oxygen atom on the partial oxidation of methane (POM) was also calculated based on a trimer model of Pd2O. For the adsorption of CHx, results showed that the presence of an oxygen atom was a disadvantage to the adsorption of CHx (x = 1–3) species. For CH4 dissociation, the process of CH2→CH + H was found to be the rate-limiting step (RSD) on both Pd2 and Pd2O. H2 was formed by the reaction of CH2 + 2H→CH2 + H2. For CO formation, it was primarily formed in the process of CH + O→CHO→CO + H on both the Pd2 and the Pd2O catalyst. Thermodynamic and kinetic calculations revealed that formation and maintainance of the oxygen atom on the Pd surface could promote a POM reaction to achieve high H2 and CO yield and selectivity. Our study provides a helpful understanding of the effect of an adsorbed oxygen atom on a POM reaction with a Pd catalyst.
Highlights
Methane (CH4 ), the main component of coalbed gas, is directly released to the environment in an amount of around 19 billion cubic meters per year [1]
Werethat considered as necessary processes for partial oxidation of methane (POM) in order to 4 dehydrogenation understand the effect of the oxygen atom that Pd-catalyzed the reaction sufficiently
The energy barriers for CH4 dissociation increased with the presence of the oxygen atom
Summary
Methane (CH4 ), the main component of coalbed gas, is directly released to the environment in an amount of around 19 billion cubic meters per year [1]. Methane activation onstudied a Pd bulk surface works was found that the effect of coadsorbed oxygen atoms tends to weaken the adsorbate–substrate largely investigated using the density functional theory (DFT) method [24,25,26,27,28]. Trevor et al observed methane activation results on Pt clusters of 2–24 atoms using time-of-flight mass on temperature. Nanocluster had aactivation large surface area and abundant defects, suggested higher reactivity for the observed methane on Pt clusters of 2–24 atoms by which using time-of-flight mass spectroscopy; oxidation of methane of theactivity-neutral bulk surface [17,30,31,32,33,34]. A Pd cluster model of dimer Pd2 was established to study the reaction mechanisms on methane activation in acluster. Plausible reaction mechanisms and the effect of an oxygen atom on POM were illuminated
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