Banca de DEFESA: MARIA KUZNETSOVA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : MARIA KUZNETSOVA
DATE: 03/05/2023
TIME: 14:00
LOCAL: Sala S-501 Bloco B - Campus Santo André
TITLE:

Microwave-assisted synthesis of bismuth niobate nanostructures with application in water splitting

PAGES: 128
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SPECIALTY: Foto-Química Inorgânica
SUMMARY:

Bismuth niobate (BiNbO4) is a visible light sensitive semiconductor oxide with properties that qualify it for photoelectrocatalytic applications. However, it is still poorly investigated for this purpose. Tungsten trioxide (WO3), on the other hand, is a widely applied semiconductor oxide in photoelectrochemical water splitting. However, it has inadequate potentials for this process. Zinc oxide has good electron mobility, resulting in devices with lower recombination rates and longer electron lifetimes. However, this material only absorbs UV light, limiting its application using visible light. To develop a strategy to overcome the limitations of these three materials, in this work, microwave-assisted synthesis protocols for heterojunctions based on bismuth niobate (BiNbO4) and tungsten (WO3) and zinc (ZnO) oxides were developed. These photocatalysts were applied as photoanodes for photoelectrochemical water splitting using simulated solar light irradiation.
For the BiNbO4 and WO3-based electrodes, it was observed that higher synthesis temperatures and irradiation powers favor the formation of the BiNbO4 orthorhombic arrangement. Additionally, the morphology of WO3 films was found to be directly controlled by the addition of weak acids in the reaction medium, allowing the formation of wrinkled rod-shaped particles and cubic particles. It was observed that the use of orthorhombic BiNbO4 associated with WO3 films formed by wrinkled rod-shaped nanoparticles increased the interaction between the semiconductors. This strategy led to the formation of a heterojunction capable of producing current densities over one magnitude higher than those of pure WO3 films.
Studies involving the BiNbO4/ZnO heterojunctions showed that BiNbO4 has a globular morphology and α-orthorhombic crystal structure. Incorporation of Pt into BiNbO4 led to structural changes. Pure ZnO films showed rod-shaped morphology and wurtzite crystal structure. However, the coating of ZnO on the conductive substrate was unsatisfactory. Nonetheless, it was possible to obtain photoelectrochemical activities for BiNbO4/ZnO heterojunctions compatible with the BiNbO4/WO3 system. However, the incorporation of Pt as a co-catalyst reduced the efficiency.
Thus, it was demonstrated that microwave-assisted synthesis is a very attractive alternative for the direct production of heterojunctions of these systems. However, it is still necessary to improve the methods to achieve fine control of the morphology.

COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 2351974 - JULIANA DOS SANTOS DE SOUZA
Membro Titular - Examinador(a) Interno ao Programa - 1623774 - KARINA PASSALACQUA MORELLI FRIN
Membro Titular - Examinador(a) Interno ao Programa - 233.691.308-90 - YVAN JESUS OLORTIGA ASENCIOS - UNIFESP
Membro Titular - Examinador(a) Externo ao Programa - 1838179 - KATIA FRANKLIN ALBERTIN TORRES
Membro Titular - Examinador(a) Externo à Instituição - LUCI ROCHA AVEIRO - IFSP
Membro Suplente - Examinador(a) Interno ao Programa - 1762430 - DALMO MANDELLI
Membro Suplente - Examinador(a) Externo ao Programa - 1545089 - DANIEL ZANETTI DE FLORIO
Membro Suplente - Examinador(a) Externo à Instituição - PAOLA CORIO