Banca de DEFESA: HENRIQUE BARBOSA GONCALVES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : HENRIQUE BARBOSA GONCALVES
DATE: 08/04/2022
TIME: 09:00
LOCAL: sala virtual
TITLE:

PRODUCTION OF HETEROJUNCTION BASED ON TANTALUM APPLIED FOR PHOTOCATALYSIS

KEY WORDS:

Photocatalysis, BiVO4, Ta2O5, NTs, Ta2O5/BiVO4.

PAGES: 163
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUMMARY:

Capable of being available for long periods of time, renewable sources are
considered the most important ways to produce energy in a clean way.
Semiconductor heterojunction formation is promising to improve photocatalytic
performance due to the synergistic combination of the best properties of each
material. The replacement of petroleum-based materials has been increasingly
evident. In the present work, a heterojunction was developed from tantalum
nanotubes and BiVO4 microstructures. A simple hydrothermal strategy to form
n-n heterojunctions of Ta2O5 nanotubes and BiVO4 microstructures prepared
separately by anodizing and hydrothermal process, respectively, is reported.
Obtaining the oxidant BiVO4 synthesized through different methods and by
adjusting the pH (2.0, 3.5 and 5.0) was investigated. The structures were
characterized by Raman, obtaining information related to short-range bonds in
the synthesized systems. The electronic structure was analyzed by UV-Vis for
BiVO4 and for Ta2O5 NTs, obtaining an average band gap for BiVO4 of 2.4 eV
and 3.8 eV for Ta2O5 NTs. The crystalline structure was characterized by X-ray
diffraction (XRD), a technique that provides information related to the
transformation kinetics of the BiVO4 and Ta2O5 NTs phases. Analysis by
transmission electron microscopy (TEM), scanning electron microscopy (SEM)
and specific surface area (BET) were used, thus corroborating the knowledge of
the morphology and surface area of the structures. Photocatalytic activity was
evaluated by photodegradation of methylene blue (AM) dye in aqueous medium
under 1.5 G AM condition (100 mW cm-2). For H2 production, photogeneration
occurred in the presence of photocatalysts for 3 hours. For the
photodegradation of AM, the Ta2O5/BiVO4-2.0H obtained via hydrothermal
showed a photodegradation of 72.3%, compared to 28.3% presented by the
sample produced by the mechanical mixture, with maintenance of 86.4% of its
photocatalytic performance after 3 cycles of photodegradation. For the
synthesized samples, we performed tests to quantify the production of H2
through gas chromatography. Photogeneration of H2 took place in the presence
of photocatalysts for 3 hours. According to the results obtained, the Ta2O5 NTs
(800°C, 850°C and 900°C) showed respectively a production of 4.4 μmol.g-1,
6.0 μmol.g-1 and 6.82 μmol.g-1 of H2. For the composite formed by
hydrothermally prepared Ta2O5/BiVO4-2.0H, 10.2 μmol.g-1 of H2 was generated
in 3h, while the mechanical mixture Ta2O5/BiVO4-M presented 2.80 μmol.g-1.
The results suggest that Ta2O5/BiVO4 is a promising material for applications in
photocatalysis, promoting sustainable energy production through hydrogen and
for the treatment of effluents containing cationic dyes.

BANKING MEMBERS:
Externo à Instituição - JEAN CLAUDIO SANTOS COSTA - UFPI
Externo à Instituição - VICTOR HUGO VITORINO SARMENTO - UFS
Externo à Instituição - FELIPE LEON NASCIMENTO DE SOUSA
Presidente - 519.487.700-59 - GIOVANNA MACHADO - UFRGS
Interno - 1301548 - MARCELO NAVARRO