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High coverage CO adsorption and dissociation on the Co(0001) and Co(100) surfaces from DFT and thermodynamics

Paper ID Volume ID Publish Year Pages File Format Full-Text
38767 45790 2016 12 PDF Available
Title
High coverage CO adsorption and dissociation on the Co(0001) and Co(100) surfaces from DFT and thermodynamics
Abstract

•The adsorption energies of CO decrease gradually with the increasing of coverage.•The coverage of CO affects the adsorption and dissociation of CO on Co surface.•On Co(0001) surfaces only molecular adsorption CO is expected.•On Co(100) surface CO adsorbs associatively and dissociatively.•CO coverage on temperature and pressure was analyzed on the basis of the thermodynamic.

The adsorption, dissociation and desorption of CO at different coverage over two Co surfaces and the corresponding equilibrium phase diagrams under different temperatures and partial pressures have been systematically investigated; here, the results are obtained using density functional theory calculations and atomistic thermodynamics together with the periodic slab model. Our results show that the saturated adsorption on both Co(0001) and (100) surface are 7/9 ML; meanwhile, on these two surfaces, the lateral repulsive interaction has an effect on the adsorption structures and the corresponding stepwise adsorption energies of these adsorbed CO molecules, and become stronger with the increasing of CO coverage, which further leads to CO migration over Co surface; moreover, the adsorption energies decrease gradually with the increasing of CO coverage until to the saturated adsorption. According to the stepwise adsorption configurations, further calculations on CO dissociation show that only molecular adsorption CO is favored over (0001) surface; whereas on Co(100) surface, when the coverage is 1/9 ML, CO dissociation is more facile than its desorption; when the coverage is from 2/9 to 5/9 ML, only the first CO dissociation is preferred, while desorption is more favored for the left CO molecules; when the coverage is equal to or greater than 6/9 ML, CO desorption will be more favorable than its dissociation. Further, the adsorption and activation of CO under different temperatures and partial pressures from atomistic thermodynamics method well illustrate the relationship between the stable CO adsorption with the temperatures and CO partial pressure on Co(0001) and Co(100) surface, respectively. Therefore, on the basis of above results, we can obtain that the surface structures mainly affect the adsorption form of CO due to the different activity towards CO, while CO coverage will affect its adsorption energies and configurations, as well as CO dissociation on Co surfaces. The calculated stretching frequencies of CO molecule at different coverage agree with the available experimental data. This study provides a more accurate and detailed information for the process of CO adsorption and activation on Co surface.

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Keywords
CO; Adsorption; Dissociation; Fischer-Tropsch synthesis; Coverage; Density functional theory
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High coverage CO adsorption and dissociation on the Co(0001) and Co(100) surfaces from DFT and thermodynamics
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 523, 5 August 2016, Pages 209–220
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us