Banca de DEFESA: ANGEL TERRAZAS PALOMINO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : ANGEL TERRAZAS PALOMINO
DATA : 28/02/2023
HORA: 10:00
LOCAL: Online
TÍTULO:

Carbon Materials for Hydrogen Storage and Polymeric Membrane Modification

PÁGINAS: 62
RESUMO:

Carbon materials such as carbon nanotubes, graphene, graphene oxide, and reduced graphene oxide present useful characteristics and properties for the development of various applications. Therefore, much research is dedicated to studying these materials and developing different technologies such as energy storage, electronic devices, virus detection, and eliminating bacteria, among others. This work investigates carbon materials' applicability in hydrogen storage and polymer modification.

Hydrogen as a fuel has an energy density three times greater than gasoline; it is also an eco-friendly and renewable fuel. Therefore, it is an alternative to replace fossil fuels. However, to develop a hydrogen-based economy, it is necessary to overcome some challenges related to its production, storage, and distribution. The most suitable method to store hydrogen is solid-state storage, which consists of the adsorption of hydrogen on the surface of a material. Carbon materials have attractive properties for storing hydrogen; in particular, graphene oxide has a very low density, high specific surface area, high porosity, and thermal stability. In addition, it has oxygenated functional groups that facilitate the formation of composite materials with favorable properties for hydrogen storage. Experimental work shows that graphene oxide decorated with titanium oxide nanoparticles has a high storage capacity compared to its components under moderate conditions of pressure and temperature. Motivated by this, we used the density functional theory to investigate the adsorption of molecular hydrogen on the surface of titanium-decorated graphene oxide composite material. We start with the study of the main functional groups of graphene oxide and use them to form different models of graphene oxide surfaces to study the adsorption of titanium on them. The results indicate that the adsorption of titanium is better on graphene with higher oxidation level. We also observe titanium oxidation on graphene oxide. The calculated adsorption energy of molecular hydrogen on the graphene oxide surface is -2.31 kJ/mol, which is within the expected values for carbon materials. As the main result, we report the calculated adsorption energies of molecular hydrogen on three different graphene oxide surfaces decorated with titanium; these energies are -37.82 kJ/mol, -12.5 kJ/mol, and -35.2 kJ/mol, which are within the adequate range (10-50 kJ/mol) to reach high hydrogen storage capacities at moderate conditions of pressure and temperature, and manage to explain the experimental results reported in the literature.

Experimentally, we succeeded in manufacturing composite membranes of Polyvinylidene fluoride (PVDF) fibers modified with carbon materials. We manufacture four types of membranes, pure PVDF, PVDF with graphene oxide, PVDF with reduced graphene oxide, and PVDF with graphite. The samples were produced using the Electrospinning technique, a simple and effective method for obtaining membranes. The influence of carbon materials on the PVDF properties was studied using various characterization techniques. Raman spectroscopy measurements identify the different carbon materials used and confirm that they were correctly incorporated into the PVDF fibers. The morphology and the diameter of the PVDF fibers of the samples were studied using scanning electron microscopy; the results indicate that there is an increase in the average diameter of the fibers in the composite membranes, possibly due to the rise in the viscosity of the polymer solution related to the presence of additives before Electrospinning. X-ray diffraction measurements and Fourier-transformed infrared spectroscopy were used to evaluate the composition of crystalline phases in polymeric membranes; the results show the presence of two crystalline phases, the alpha phase, which is dominant in all samples and the beta phase, which decreases when carbon materials are added. X-ray photoelectron spectroscopy was used to study the chemical states of the fiber surface.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 2226644 - LUCAS ALMEIDA MIRANDA BARRETO
Membro Titular - Examinador(a) Interno ao Programa - 1676360 - ANA MELVA CHAMPI FARFAN
Membro Titular - Examinador(a) Interno ao Programa - 1671292 - SYDNEY FERREIRA SANTOS
Membro Titular - Examinador(a) Externo à Instituição - RENATO BATISTA DOS SANTOS
Membro Suplente - Examinador(a) Interno ao Programa - 1838179 - KATIA FRANKLIN ALBERTIN TORRES
Membro Suplente - Examinador(a) Interno ao Programa - 1282172 - ROBERTO GOMES DE AGUIAR VEIGA