Banca de QUALIFICAÇÃO: GILSON DOS SANTOS COSTA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE: GILSON DOS SANTOS COSTA
DATA: 06/10/2025
HORA: 08:30
LOCAL: Auditório do Programa de Pós-Graduação em Química/UFPI
TÍTULO: Semiconductor oxides and strategies to improve their photoelectrocatalytic activities: heterojunction and oxygen vacancies
PALAVRAS-CHAVES: Progesterone photodegradation; Heterojunction; Oxygen vacancies; Photoelectrochemistry
PÁGINAS: 45
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Físico-Química
ESPECIALIDADE: Química do Estado Condensado
RESUMO:

The use of semiconductor materials for the development of technologies aimed at environmental applications has gained prominence in recent years. Semiconductors have been investigated mainly as films in photocatalytic and photoelectrocatalytic processes, which depend on the surface properties of the material. The optical, morphological, and structural properties of semiconductors influence the material’s catalytic efficiency in energy conversion. According to band theory, the generation of electron-hole charges (e-/h+) can be considered the initial stage of catalysis processes. However, a high charge recombination rate can reduce the performance of photocatalysts. Therefore, a strategy was developed to overcome this disadvantage, among which we can mention heterojunction and introduction of vacancies in semiconductors. In general, heterojunction can be understood as the union of two or more semiconductor materials with different structures. Studies have shown that charge separation is more efficient in heterojunctions, which favors the formation of reactive oxidative species, improving the photocatalytic process. This manuscript will outline the concepts of heterojunctions and their significance in the development of technologies that can remediate degraded environments and generate clean energy. In addition, a complementary study describes the synthesis and investigation of the photoelectrochemical response and photocatalytic activity of CuWO4 films produced under five atmospherically conditioned conditions as photoanodes for the removal of progesterone from wastewater. The addition and control of oxygen vacancies (OV) in semiconductor films is a strategy that aims to reduce charge recombination and favor the photocatalytic activity of the material. The bare and coupled films were deposited by drop-casting from polymeric resin and calcined by alternating the calcination atmosphere with air and pure N2. The structural, morphological, and optical properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis spectroscopy, respectively. The pristine (CuW-0) and modified (CuW-x; x = 25, 50, 75 or 100) films exhibited irregular morphological, monoclinic structures and interesting optical properties in the visible region. Compared with the CuW-0, the CuW-x films showed an improved photoelectrochemical response and superior photoelectrocatalytic performance for progesterone degradation under polychromatic light irradiation. Electrochemical measurements show that the introduction of oxygen vacancies increased the charge transfer rate at the electrolyte-electrode interface and the lifetime of charge recombination at the electrode. Thus, photoelectrocatalytic studies demonstrated superior efficiency in progesterone photodegradation for the vacancy film (CuW-75), which achieved 19% removal of the persistent organic pollutant. The film remained active during the evaluation of three reuse cycles.

MEMBROS DA BANCA:
Presidente - 794.***.***-87 - REGINALDO DA SILVA SANTOS - UESPI
Interno - 1998602 - EVERSON THIAGO SANTOS GERONCIO DA SILVA
Interno - 1714193 - JOSE MILTON ELIAS DE MATOS
Externo à Instituição - 877.***.***-49 - GILVAN MOREIRA DA PAZ - IFPI