Banca de DEFESA: IGOR MATHEUS DE AMORIM SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : IGOR MATHEUS DE AMORIM SILVA
DATE: 22/06/2023
TIME: 14:00
LOCAL: PLATAFORMA RNP
TITLE:

Study of structural, surface and photocatalytic properties of SnO2, CuO and SnO2/CuO hetejunctions

KEY WORDS:

Heterogeneous Photocatalysis; Heterojunctions; SnO2/CuO; Eosin Y; Methylene Blue; visible light.

PAGES: 108
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUMMARY:

In recent years, scientific interest has grown in the synthesis of p-n heterojunctions for photocatalytic applications and a good candidate for photocatalyst is SnO2 because it is stable, non-toxic and economically viable. However, tin oxide when used individually in reactions photocatalytic plants may present internal recombinations and these recombinations are not favorable because they prevent the reaction from proceeding. SnO2 when combined with oxides of lower bandgap energy tend to form semiconductor heterojunctions, which have the ability to narrow the tin oxide bandgap and possibly decrease recombination rates internal processes, culminating in an improvement in reaction performance. The literature has reported the preparation of SnO2/CuO heterojunctions that have potential for energetic activation by visible light. The objective of this work was to insert Cu2+ ions into the SnO2 structure, creating p-n heterojunctions and to monitor the crystalline, electronic, surface and photocatalytic properties of the materials. The pure SnO2 and CuO oxides were obtained by the precipitation method, the heterojunctions were obtained by the coprecipitation method with 5, 15 and 25% of Cu2+ and characterized by several techniques in order to know their physicochemical characteristics. XRD revealed that the insertion of copper changes the structure of SnO2 to the crystallinity of the sample, since when increasing the content of Cu2+ cations by 5, 15 and 25%, a decrease in the crystallite size of 9.23, 7.45 and 7.13, respectively. The increase in structural defects causes a decrease in the crystallinity of the materials, this decrease is correlated with the increase in the surface area determined by the N2 physisorption analysis by the B.E.T method. It was inferred through
diffuse reflectance spectroscopy that the insertion of Cu2+ to SnO2 creates additional levels of energy in the bandgap of heterojunctions, as it was noted the emergence of a new absorption band located at 750 nm, accompanied by a shift to the red region of the spectrum, the estimated bandgap values decreased with increasing copper content, reaching 2.3; 2.0 and 1.5 eV for the heterojunctions SnO2/CuO 5%, SnO2/CuO 15%, SnO2/CuO 25%, respectively. The photocatalysts synthesized in this work were applied in the photodegradation of methylene blue (cationic dye) and eosin Y (anionic dye). The reaction results obtained reveal that crystallinity is a determining factor in the photocatalytic activity of this system, as the materials with the highest degree of crystallinity, SnO2 and SnO2/CuO 5%, obtained greater reaction efficiency against the photodegradation of methylene blue, 55 and 53%, when compared to 37, 37, 17% of the SnO2/CuO 15%, SnO2/CuO 25% and CuO materials, respectively. The SnO2 and SnO2/CuO 5% materials also showed greater reaction efficiency in the photodegradation of eosin Y, 77 and 69%, compared to 51, 38 and 30% of the SnO2/CuO 15%, SnO2/CuO 25% and CuO materials, respectively. However, the results of this work show that investigating the photocatalytic properties of SnO2, CuO and p-n SnO2/CuO heterojunctions can positively influence the design of efficient materials for heterogeneous photocatalysis induced by visible light

BANKING MEMBERS:
Interno(a) - 1348288 - MARIO ROBERTO MENEGHETTI
Presidente - 1515173 - SIMONI MARGARETI PLENTZ MENEGHETTI
Externo(a) ao Programa - 3298566 - THATIANE VERISSIMO DOS SANTOS MARTINS
Interno(a) - 1697766 - WANDER GUSTAVO BOTERO