Banca de DEFESA: PAULO HENRIQUE DA SILVA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : PAULO HENRIQUE DA SILVA
DATE: 20/08/2025
TIME: 08:00
LOCAL: REMOTO
TITLE:

Study of the Electrochromic Properties of MoO3 obtained via Sol-Gel by Ion Exchange

KEY WORDS:

electrochromism; molybdenum oxide, sol-gel

PAGES: 73
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SUMMARY:

Transition metal oxides (TMO) have currently attracted a lot of attention due to their electronic structure for the formation of various oxides with electrochromic characteristics. In particular, MoO3 is a highlighted TMO as it has a wide oxidation state (+2 to +7) and electrochromic properties of interest for use in electronic devices. In this work, MoO3 was obtained through sol-gel description by ion exchange, using a solution containing sodium molybdate, which was percolated in a cation exchange column. Such solutions were used at different pH and in different concentrations: pH = 2, 4 and 5; and concentrations: 0.05, 0.10, 0.20, 0.30, 0.40 and 0.50 mol.L-1. After obtaining the solutions containing MoO3, they were deposited on a substrate of polyethylene terephthalate (PET) and tin-doped indium oxide (ITO) and characteristics using X-ray diffractometry (XRD) techniques and spectroelectrochemical studies using as techniques of spectrophotometry in the Ultraviolet-visible (UV-Vis) region in conjunction with cyclic voltammetry (VC). From the diffractograms, the presence of two polymorphic phases of MoO3 was observed: a stable phase α-MoO3 in its orthorhombic form and a metastable phase h MoO3 that correspond to its hexagonal structure. The optical analyzes showed characteristic absorption profiles for MoO3 in the range between 300 – 800nm. From the absorbance values found, for MoO3, band gap energy values were obtained with values between 2.58 – 3.99 eV, which were useful in the energy assessment in the transfer of electrons between the conduction and conduction bands valence between oxygen and molybdenum. From the cyclic voltammograms, anodic and cathodic peaks were collected according to each film prepared. The variation in pH and concentration in the synthesis of MoO3 demonstrated to have an influence on the electrochemical responses, structure and electrochromic property of the material, with some films having optically irreversible color changes during the spectroelectrochemical tests, other two samples showing optically reversible color changes , and the thin films did not change color, demonstrating that the change in the pH of the synthesis medium, as well as the concentration, significantly alters the structure of the material, modifying its optical and electrochromic properties.

BANKING MEMBERS:
Interno - 1444161 - DANE TADEU CESTAROLLI
Presidente - 1742429 - ELIDIA MARIA GUERRA
Externo à Instituição - JÚLIO CÉSAR JOSÉ DA SILVA - UFJF
Externo à Instituição - ROGERIO DE OLIVEIRA - IFMG
Interno - 1942302 - VICTOR AUGUSTO ARAUJO DE FREITAS