Theoretical Investigation of Adsorption & Reactions of H2 , O2&HCO2H on Single Crystal Alloys Surfaces Based on UBI-QEP Method

Shokoohi, Mahdiyeh | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47653 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Gobal, Fereydoon
  7. Abstract:
  8. The aim of this project is to investigate the mechanisms of absorption and reactions of H2, O2, HCO2H on the single crystal surfaces of transition metals alloys such as Ni-Cu and Ni-Fe and …as well as the ability to control the properties of the mentioned alloys with change in constitutions percentage. In order to achieve the objectives, Unity Bond Index-Quadratic Exponential Potential, UBI-QEP method have been employed. Using this method, the thermodynamic parameters (heat of adsorption and reaction enthalpy changes) and kinetic parameters (activation energy of the reaction) can be calculated, and using these results, intermediate, and as a result, the mechanism of heterogeneous catalytic reactions can be predicted. Also, the results of this method are consistent with experimental results. By studying the processes of decomposition of formic acid on the surfaces of Cu(111), Ni (111) and Fe (111), it appears that intermediates of this process in all three cases is HCOOs, but the final products are different. The surfaces Ni(111) and Fe (111) lead to the production of CO2 and CO, which this feature also seen in their alloys. However, at surface Cu(111), only CO2 is produced, and with increase of the percentage of copper in the alloy, this feature is also morepronounced on the alloys. On the other hand, this process on the surface of copper compared to iron and nickel, require less activation energy and this feature is also observed in the Ni-Cu alloy. By studying the reaction process of H2 and O2 on the surface of nickel, copper, platinum and gold, it is clear that, almost production of hydrogen peroxide on the surfaces of nickel, copper, iron and platinum is impossible. It is shown there is the possibility to produce hydrogen peroxide on the gold surface, but its efficiency is very low and the final product will be a mixture of water and hydrogen peroxide
  9. Keywords:
  10. Heterogeneous Catalysis ; Formic Acid ; Hydrogen Peroxide ; Unity Bond Index-Quadratic Exponential Potential (UBI-QEP)Theory ; Single Crystals

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