Hydrocarbon dissociation on metal surfaces

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master_Jafari_Maryam_2025.pdf (1.12 MB)

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School of Chemical Engineering | Master's thesis
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Date

2025-09-29

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Major/Subject

Chemistry

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Degree programme

Master's Programme in Chemical, Biochemical and Materials Engineering

Language

en

Pages

54

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Abstract

Hydrogen, due to its efficiency and producing water by burning, is a promising candidate as energy carrier. However traditional production methods are energy-intensive and produce significant amount of carbon dioxide. As using catalytic decomposition of light hydrocarbons offers a lower-emission alternative and produce solid carbon, it appears to be a promising method. To better understand the mechanism of this method, stepwise hydrogen dissociation of ethane and carbon-carbon coupling was modelled on Pt(111) surface, using density func-tional theory and climbing-image nudged elastic band. A clear trend was observed: hydrogen dissociation was thermodynamically and kinetically favourable at initial steps however becomes more difficult as more hydrogen was removed. In this process, the carbon skeleton hybridization goes from sp³ toward sp²/sp character. This result in a stronger bond between carbon and hydrogen. After overcoming the activation barrier of the last steps and full dehydrogenation is achieved, the coupling of unsaturated carbon fragments is thermodynamically favourable. This is consistent with graphene nucleation on platinum. Computed results show that the hydrogen removal requires less energy if a catalyst be able to electronically weaken the late-stage C–H bonds. Catalysts with steps or defects also require less energy for hydrogen removal. The study of hy-drogen dissociation on Pt(111) surface provides the mechanisms of the reactions and workflow of DFT and Cl-NEB, which helps improving the existing gaps.

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Supervisor

Laasonen, Kari

Thesis advisor

Laasonen, Kari

Keywords

hydrogen dissociation, density functional theory, Cl-NEB, catalysts, surface reaction, Pt(111)

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https://urn.fi/URN:NBN:fi:aalto-202510228524

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[dipl] Kemian tekniikan korkeakoulu / CHEM