Banca de DEFESA: CLEONILSON MAFRA BARBOSA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : CLEONILSON MAFRA BARBOSA
DATA : 31/07/2017
HORA: 13:00
LOCAL: Auditório do NUPEG I
TÍTULO:

SYNTHESIS AND CHARACTERIZATION OF MIXED NIOBIUM AND TANTALUM ELECTROCATALYSTS DOPED WITH Co, Cu AND Ni PRODUCED FROM COLUMBITE/TANTALITE.

PALAVRAS-CHAVES:

Columbite/Tantalite. Catalysts. Methanol. Ethanol. Fuel cells.

PÁGINAS: 102
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

This paper proposes an alternative route for producing catalysts for methanol and ethanol oxidation reactions to be applied on fuel cells. Those catalysts are based on oxides and precursors of mixed niobium and tantalum nanostructured materials in their pure and doped (with Co, Cu or Ni) forms. These materials are obtained from columbite/tantalite, which is the base mineral for Nb, Ta, extracted from Rio Grande do Norte’s mineral resources. At first, an experimental planning for the complete purification of the mineral was performed. After purification, 10%wt. doping with each of the metals, and thermal treatment at three different temperatures (110,400 and 600°C) was carried out. Un-doped purified oxides were then subject to complexation process followed by metal addition (doping) and thermal treatment. Purified and thermally treated mineral was characterized by X-Ray Fluorescence (XRF) and X-Ray Diffraction and complete purification was attained. Complex precursors were evaluated on the basis of XRD, Infra-Red Spectroscopy (IR), thermal behavior (TG/DSC and DTA) and morphology (Scanning Electron Microscopy) and presented particle sizes under 0.2 µm, elevated weight loss (76.6%) and a porous structure of irregular shape. Pure and doped catalysts were characterized on XRD, XPS (X-Ray Excited Photon Spectroscopy), SEM and TEM (Transmission Electron Microscopy) basis, presenting indication of catalytic properties interesting for oxidation reactions, such as quick surface reduction. Electrical evaluation of the catalysts was performed according to Differentia Pulse Voltammetry (DPV) with the use of micro sensors during alcohol oxidation reactions. These analyses indicated the excellent conducting characteristics of the materials as electric current flow was increased in two orders of magnitudes in comparison to gold electrodes. The best catalytic behaviors were observed when dopping was performed with copper, followed by nickel, cobalt and without dopant addition. Therefore, the synthesized materials presented characteristics that indicate their suitability for use as fuel cells electrodes.

MEMBROS DA BANCA:
Externo à Instituição - ANA KARLA COSTA DE OLIVEIRA - IFRN
Externo à Instituição - ARIADNE DE SOUZA SILVA - UFRN
Presidente - 349801 - CARLSON PEREIRA DE SOUZA
Externo à Instituição - FABIO GARCIA PENHA - IFRN
Interno - 345842 - UILAME UMBELINO GOMES