Banca de QUALIFICAÇÃO: PATRICIA MARIA GONCALVES

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : PATRICIA MARIA GONCALVES
DATE: 10/03/2023
TIME: 09:00
LOCAL: meet.google.com/jvc-qdqs-xzx
TITLE:

Study of the combination WO3/r-OG, for application in lithium-ion batteries

KEY WORDS:

lithium-ion batteries, citric acid, oxalic acid, pH, cyclic voltammetry

PAGES: 79
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SUMMARY:

Due to the high energy demand and demand for clean, efficient and safe energies, new materials have been tested and improved for direct use in lithium-ion batteries (LIBs). Tungsten oxide (WO3) and reduced graphene oxide (r-OG) are two materials that, separately, have good applicability in LIBs, in addition to not being harmful to the environment. Thus, the synthesis and study of the WO3/r-OG composite becomes interesting, for a possible application in LIBs. Thus, this work aimed to synthesize and study the materials obtained, in addition to proving under which experimental conditions, there is the most electrochemically efficient composite for use in LIBs. Through the hydrothermal method, WO3 was obtained, through pH variation and use of acids, citric and oxalic acid, in order to guide the growth of WO3 structures. The hydrothermal method was chosen due to its simplicity, economy and efficiency in obtaining nanomaterials. This method also made it possible to obtain the composite, WO3/r-OG. For the synthesis of r-OG, the modified Hummer's method was used. X-ray diffraction analyzes confirmed the presence of two distinct crystalline phases for WO3, the hexagonal phase (h-WO3) and the monoclinic phase (m-WO3), when there is pH variation. It also confirmed the obtaining of r-OG and the formation of the WO3/r-OG composite. The infrared spectra evidenced the presence of groups related to the materials of interest. Images obtained by scanning electron microscopy showed different surfaces for WO3, depending on the type of acid employed in the synthesis. It was also possible to observe the surface of the r-OG and the WO3/r-OG composite, which present roughness. Through cyclic voltammetry, it was possible to characterize all samples, study the electrochemical behavior of the separated materials and prove that the composite WO3/AC/r-OG, synthesized at pH 2.0 and the composite WO3/AO/r- OG, synthesized at pH 1.5 showed the best electrochemical performances, with regard to stability and total charge.

BANKING MEMBERS:
Presidente - 1444161 - DANE TADEU CESTAROLLI
Externa à Instituição - GLAURA GOULART SILVA - UFMG