Banca de DEFESA: GABRIEL DOS SANTOS VASCONCELOS
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.STUDENT : GABRIEL DOS SANTOS VASCONCELOS
DATE: 02/06/2025
TIME: 09:30
LOCAL: Presencial
TITLE:
Synthesis and study of the high-entropy oxide (Fe₀.₂Ni₀.₂Co₀.₂Al₀.₂Zn₀.₂)₃O₄ via the sol-gel method assisted by polyvinylpyrrolidone (PVP) and its application as a electrocatalyst for the oxygen evolution reaction (OER)
KEY WORDS:
High-entropy spinel, oxygen evolution reaction (OER), (Fe₀.₂Ni₀.₂Co₀.₂Al₀.₂Zn₀.₂)₃O₄, structural characterization, Mössbauer spectroscopy, magnetic properties.
PAGES: 95
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:
High-entropy oxides (HEOs) have emerged as a promising class of functional materials due to their tunable electrochemical and magnetic properties, with potential applications in catalysis, energy storage, and electronic devices. In this context, the present study aims to synthesize and perform a detailed characterization of the high-entropy oxide (Fe₀.₂Ni₀.₂Co₀.₂Al₀.₂Zn₀.₂)₃O₄, referred to as HEO-600, synthesized at 600 °C via the sol-gel method assisted by polyvinylpyrrolidone (PVP). Additional samples were produced at higher temperatures, revealing the formation of distinct crystalline phases, including spinel- and rock-salt-type structures. Structural and compositional characterization was carried out using multiple techniques, including X-ray diffraction (XRD), field-emission scanning electron microscopy (FEG-SEM) with energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XPS analysis confirmed the equimolar composition of elements in the HEO-600 sample, while EDS analysis revealed a homogeneous distribution of cations, corroborating the formation of a homogeneous solid solution. TEM micrographs showed well-dispersed, non-aggregated particles with an average size of 9.2 nm. The magnetic properties of the HEO-600 sample were investigated through Mössbauer spectroscopy, direct current (DC) magnetometry, and alternating current (AC) magnetometry. The Mössbauer spectrum indicated that iron ions were distributed between tetrahedral (A) and octahedral (B) sites in a 43% to 57% ratio, confirming a partially inverted spinel structure. Magnetic susceptibility measurements (DC and AC) revealed superparamagnetic behavior at room temperature, along with the presence of a spin-glass-like phase, with a transition temperature at 206 K. This magnetic phase was suppressed under an external field of approximately 4300 Oe, highlighting the complexity of magnetic interactions in the system. In addition to structural characterization, spectroscopic and electrochemical analyses were conducted to evaluate the potential of the HEO-600 sample as a catalyst for the oxygen evolution reaction (OER). Ultraviolet-visible (UV-Vis) spectroscopy and Fourier-transform infrared (FTIR) spectroscopy provided further insights into the vibrational configuration and chemical bonding within the oxide. Electrochemical experiments demonstrated that the HEO-600 sample exhibits promising OER performance, with an overpotential of 358 mV at a current density of 10 mA cm⁻². This value indicates competitive catalytic activity compared to other high-entropy transition metal oxides. Thus, this study significantly advances the understanding of the structural, magnetic, and electrochemical properties of high-entropy oxides. The findings not only expand knowledge on the correlation between synthesis, structure, and properties of these materials but also highlight their potential for technological applications in electrochemical catalysis, particularly in renewable energy conversion and storage.
COMMITTEE MEMBERS:
Presidente - ***.121.804-** - UILAME UMBELINO GOMES - UFRN
Interno - 2414250 - MEYSAM MASHHADIKARIMI
Externo ao Programa - 1674707 - MARCO ANTONIO MORALES TORRES - UFRNExterna à Instituição - ARIADNE DE SOUZA SILVA - IFRN
Externo à Instituição - RAFAEL ALEXANDRE RAIMUNDO