Date of Publication

2006

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics

Subject Categories

Physics

College

College of Science

Department/Unit

Physics

Thesis Adviser

Romeric F. Pobre

Defense Panel Chair

Reuben V. Quiroga

Defense Panel Member

Eduardo C., Cuansing Jr.
Nikko P. Quevada
Emmanuel T. Rodulfo
Cristine DLR. Villagonzalo

Abstract/Summary

One promising energy source is hydrogen based fuel cell specifically Polymer Electrolyte Fuel Cell (PEFC) whose by-product is a non-toxic solvent water. The researchers considered the possibility of using oxygenase-based nanomaterials (Iron (II) porphyrin) in the cathode electrodes of PEFCs, where oxidation reduction reaction takes place (ORR). Specifically, we want to see the effects of halogens (F, Cl, and Br) placed on messo-, and beta- positions of iron porphyrins, on the geometry, electron and spin density, total energy and binding energies of the said molecule by means of Density Functional Theory (DFT) for the proposed catalyst of the PEFC electrodes. The researchers found that adding halogens (Fluorine, Chlorine, and Bromine) to the subsequent positions (messo- and beta-) of iron porphyrin can lower the total energy thus making the molecule more stable. The results also show that increasing number of electronegative atoms lead to greater electron withdrawal from the non-halogen atoms in the FeP resulting to lower total energy. Fluorine being the most electronegative gives the lowest total energy followed by chlorine and bromine. Moreover, halogenations at messo- sites can cause bending of the iron porphyrin while halogenations on beta- sites protect structural deformation on the iron porphyrin upon oxygen adsorption. The position of the halogens, whether opposite or adjacent sides on both messo- and beta- positions, do not account for significant changes in total energy. We also found out that triplet state of halogenated derivatives that have small relative energy gap will correspond to lower binding energies and for singlet state, molecules with small relative energy gap will have higher relative binding energy. The energy gap and binding energies of halogenated iron porphyrin depends greatly on the electron density distribution of the molecule. These can be seen through HOMO/LUMO plot of the molecule being studied.

Abstract Format

html

Language

English

Format

Electronic

Accession Number

CDTG004282

Shelf Location

Archives, The Learning Commons, 12F Henry Sy Sr. Hall

Physical Description

x,2-28 leaves ; 28 cm.

Keywords

Density functionals; Halogens; Porphyrins; Oxidation-reduction reaction

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