AB initio modelling of materials proper ties for catalytic and device applications

Date

2017

Author

Şensoy, Mehmet Gökhan

Metadata

Show full item record

Item Usage Stats

131
views

0
downloads

The first-principles computations based on density functional theory is used to study the adsorption properties and the activation of CO, CO2 and H2O on gamma-Al2O3(100) surface. A systematic study has been conducted to identify the most stable adsorption sites for both mono- and di-atomic Pt clusters. Several stable adsorption geometries have been identified for the species as well as introduces their interaction with Pt clusters and the support. In this context, analysis of the adsorption properties allows us to establish the most stable configuration in a reaction mechanism. Another important factor in the reactivity of catalyst is the support material which has a great influence on the efficiency and activity of a catalytic reaction. Transition metal carbides (TMCs) are a good alternative as a support material in a catalytic reaction. Therefore, studying on the surfaces of platinum carbide (PtC) as a support material is being important. While the bulk structure of zincblende (ZB) PtC has been investigated several times, a detailed understanding of the electronic and structural properties of its low-index surfaces is lacking. Within this study, we present an ab-initio investigation of the properties of five crystallographic ZB PtC surfaces, Pt/C-terminated PtC(100), PtC(110) and Pt/C-terminated PtC(111). Adsorption geometries have been identified for the atomic oxygen, and its interaction with surface atoms is characterized in terms of adsorption energies and the nature of bonding between the adsorbed and surface atoms. Calculated vacancy formation energies indicate facile C removal (exothermic) on the ZB PtC(111) surface, and Pt-vacancy formation is endothermic with respect to the vacancy formation energy. An ab-initio thermodynamical analysis shows that the most stable surfaces are the Pt-terminated PtC(100) and PtC(111) surfaces, and the higher oxygen coverages of PtC(100) surface are stable even at temperature as high as 3000 K. In addition to the catalytic properties of an oxide surface and TMCs, we have also studied the interaction of chlorine (Cl) atom with graphene sheet and H-terminated graphene nanoribbons (GNRs) based on density functional theory (DFT). We have discussed the electronic and structural properties of adsorbed Cl atom on pristine and defective graphene under applied electric field. We have found that the most stable adsorption configurations are the on-site geometry and hollow site aligned parallel to the graphene plane for single and molecular Cl atom (Cl2), respectively. The energy band structures are also performed to understand the nature of size effect including the effects on the magnetization, adsorption behavior of single Cl atom and charge transfer in graphene nanoribbons with zig-zag and armchair edges.

Subject Keywords

Catalysts., Adsorption., Graphene., Water-gas., Nanostructures., Transition metal carbides.

URI

http://etd.lib.metu.edu.tr/upload/12621317/index.pdf
https://hdl.handle.net/11511/26534

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Novel RDX-Based Cage and Cage-Like Nitramines Türker, Burhan Lemi; Bayar, Caglar Celik; Turhan, Hamza (Informa UK Limited, 2013-10-01) 1,3,5-Trinitroperhydro-1,3,5-triazine (RDX)-based cage and cage-like nitramines in which two RDX molecules are linked to each other via three and two carbon atoms, respectively, have been investigated computationally using density functional theory (DFT) at a B3LYP/6-31G(d,p) theoretical level. The study focused on finding out how the quantum chemical and detonation properties of RDX change if two RDX molecules come together and form these structures. Both considered nitramines exhibited higher heats of for...
Ab initio modelling and investigation of the effects of magnesium oxide surface modifications on single atom catalysis systems Kallem, Aydoğa; Toffoli, Hande; Canbay, Cahit; Department of Micro and Nanotechnology (2023-1-23) An emerging technology, namely Single Atom Catalysts (SACs) have the potential to bridge the positive characteristics of both heterogenous and homogenous catalysts. In order to create more efficient SACs, it is necessary to understand the metal support interaction (MSI) at the molecular level, which seriously affects the performance of SACs. In this study, the effects of surface modifications on the catalytic performance of SACs were examined via Density Functional Theory (DFT) to gain a deeper understandin...
Thermal decomposition of polystyrene-b-poly(2-vinylpyridine) coordinated to co nanoparticles Elmaci, Ayşegül; Hacaloğlu, Jale; Kayran, Ceyhan; Sakellariou, Georgios; Hadjichristidis, Nikos (2009-11-01) Direct pyrolysis mass spectrometry analyses of polystyrene-block-poly(2-vinylpyridne), PS-b-P2VP, indicated that the thermal degradation of each component occurred independently through the decomposition pathways proposed for the corresponding homopolymers; depolymerization for PS and depolymerization and loss of protonated oligomers for P2VP by a more complex degradation mechanism. On the other hand, upon coordination to cobalt nanoparticles, thermal decomposition of the P2VP blocks was initiated by loss o...
Surface energy and excess charge in (1x2)-reconstructed rutile TiO2(110) from DFT plus U calculations Unal, Hatice; METE, ERSEN; Ellialtıoğlu, Süleyman Şinasi (2011-09-09) Physically reasonable electronic structures of reconstructed rutile TiO2(110)-(1x2) surfaces were studied using density functional theory (DFT) supplemented with Hubbard U on-site Coulomb repulsion acting on the d electrons, the so called DFT + U approach. Two leading reconstruction models proposed by Onishi and Iwasawa [Surf. Sci. Lett. 313, 783 (1994)] and Park and coworkers [Phys. Rev. B 75, 245415 (2007)] were compared in terms of their thermodynamic stabilities.
Theoretical and experimental investigation of water-gas shift reaction over supported copper/iron oxide catalysts Yalçın, Özgen; Önal, Işık; Department of Chemical Engineering (2017) Density functional theory calculations were carried out to investigate the role of the chromium and copper, which were demonstrated to act as textural and catalytic promoters, respectively, for the Fe3O4-Cr2O3-CuO catalyst system by in situ experimental studies at the atomic scale. There is a minor effect of Cr on the dissociative adsorption of H2O, but no effect on CO adsorption on the Feoct2 termination of Fe3O4 (111) surface indicating that Cr does not act as a chemical promoter. Copper promotion of the ...

Citation Formats

M. G. Şensoy, “AB initio modelling of materials proper ties for catalytic and device applications,” Ph.D. - Doctoral Program, Middle East Technical University, 2017.