Banca de DEFESA: THIAGO ANDRE SALGUEIRO SOARES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : THIAGO ANDRE SALGUEIRO SOARES
DATE: 19/05/2022
TIME: 14:00
LOCAL: plataforma virtual
TITLE:

DEVELOPMENT OF SINGLE-STEP ELECTROCHEMICAL SYNTHESIS ROUTES IN THE FORMATION OF NANOTUBES OF TiNb2O7, CoTiO3/TiO2 and GNF-1/TiO2 APPLIED TO PHOTOELECTROCHEMICAL CELLS

KEY WORDS:

Nanotubes, anodizing, TiO2, TiNb2O7, CoTiO3, graphene.

PAGES: 108
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

The present work aims to present three different electrochemical synthesis routes for the fabrication of TiO2-based nanotubular mixed oxides. The first work presents the synthesis of nanotubes from a Ti-70Nb alloy, by the anodizing method. The influence of different potentials on the formation of nanotubes and the effect of different heat treatment temperatures were studied. The SEM images and EDS mapping showed the distribution of Ti and Nb elements along the tubular matrix demonstrating that the anodized nanotubes consist of a uniform mixture of TiO2 and Nb2O5. The optical band gap of TiNb2O7 was 2.88 eV. These oxide mixtures were applied in the photocatalytic generation of H2 under solar irradiation; where the heat treated sample at 800 °C resulted in a production rate of 61 μmol.h-1.g-1. The second proposes the synthesis of hybrid CoTiO3/TiO2 perovskite nanotubes synthesized by a simple pulsed anodization process. Conventional Ti anodizing electrolyte was modified with Co2+ cations. The positive voltage cycle helps to form nanotubes due to the oxidation/dissolution of Ti and the negative cycle helps to simultaneously insert Co2+ into the tubular matrix in a controllable way. Argon-flow heat treatment formed the CoTiO3/TiO2 heterojunction resulting in a 10-fold increase in photocurrent under simulated sunlight compared to conventional TiO2 nanotubes. The third work presents a new strategy to incorporate a graphene structure (GNF-1) into TiO2 by means of a one-step anodizing electrophoretic
deposition assisted by the anionic surfactant sodium dodecyl sulfate (SDS). This approach leads to the formation of an effective interface between TiO2 and GNF-1 based on the simultaneous anodic growth of nanotubular TiO2 and the electrophoretic movement of negatively charged GNF-1 surfactant colloids. The TNT-GNF-1 electrode exhibits improved performance as a photoanode, with an increase in photocurrent density of up to 45% over the pure TiO2 electrode. The faradaic efficiency of the TiO2 and TiO2-GNF-1 photoanodes to generate O2 is 70% according to a collector-generator dual electrode system, demonstrating that the increase in the photocurrent response of the TiO2-GNF-1 photoanodes is not due to the oxidation of GNF-1, but from the synergistic effect between the materials.

BANKING MEMBERS:
Externo à Instituição - RENATO VITALINO GONCALVES - USP
Externo à Instituição - DENILSON DE VASCONCELOS FREITAS
Presidente - 519.487.700-59 - GIOVANNA MACHADO - UFRGS
Interna - 2163324 - JOANNA ELZBIETA KULESZA
Externo à Instituição - MARCO ANTONIO SCHIAVON - UFSJ