Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.771663
Title: Computational studies of the adsorption of hydrazine on Cu surfaces
Author: Sarabadani Tafreshi, S.
ISNI:       0000 0004 7659 3375
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2015
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Abstract:
This thesis presents a comprehensive computational study of the molecular and dissociative adsorption of hydrazine (N2H4) on low-index perfect and defective copper surfaces, using the density functional theory calculations with long-range dispersion correction (DFT-D2). Firstly, we have studied the adsorption of hydrazine on low-index planar copper surfaces, where (111) is found to be the most stable surface, whilst (110) surface is the least stable. DFT-D2 calculations with a correction for the van der Waals interactions result in significant enhancement of molecule-substrate binding. Secondly, DFT-D2 has been used to simulate the interaction of hydrazine with low-index defect-containing copper surfaces. We have studied three types of defects at the surfaces: monoatomic steps, Cu-adatoms and vacancies, where our calculations show that the adsorption energy increases as the coordination of the adsorption sites decreases, with the strongest adsorption energy found on the stepped (110) surface. Thirdly, we have investigated the arrangement of multiple hydrazine molecules upon adsorption onto the Cu(111) surface, showing that the main contributors to the assembly of the hydrazine layers are the binding interactions between the adsorbates and the substrate and the organisation of the N2H4 monolayers is primarily due to the long-range interactions. Furthermore, we have simulated the dissociative adsorption of hydrazine on the planar and stepped Cu(111) surfaces. We found that hydrazine prefers to form NH2 via N-N bond decoupling, where the NH2 molecule reacts fairly easily with co-adsorbed NH2 to form NH3, as well as with N2Hx (x=1-4) by subtracting hydrogen to produce NH3 and N2 molecules. Finally, we have constructed a microkinetic model to develop our understanding of the catalytic process of N2H4 dissociation on the planar Cu(111) surfaces. The temperature programmed reaction and batch reactor simulations were simulated, showing that the NH3 and N2 are the dominant gaseous products, while H2 is the minor gaseous product.
Supervisor: de Leeuw, N. H. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.771663  DOI: Not available
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