Banca de DEFESA: MAURICIO ROCHA DE BRITO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : MAURICIO ROCHA DE BRITO
DATE: 16/10/2025
TIME: 09:00
LOCAL: Remoto
TITLE:

COMPOSITES BASED ON NIOBIUM AND NON-NOBLE METALS AS PHOTOCATALYSTS UNDER VISIBLE LIGHT

KEY WORDS:

Niobium pentoxide, photocatalysis, non-noble metals, organic-inorganic composites, decolorization

PAGES: 107
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUMMARY:

Aiming at the synthesis of new visible-light active photocatalysts, this work focused on preparing six photocatalytic composites based on three crystallographic morphologies of niobium pentoxide combined with non-noble metals (aluminum or copper). The synthetic procedure involved preparing an organic matrix of fructose-derived oligomers with non-noble metal precursor salts in an ethylene glycol medium, followed by addition of an Nb₂O₅/ethylene glycol suspension at 105 °C. Bandgap energies were determined using the Tauc plot method from UV-Vis diffuse reflectance spectroscopy data, showing that all composites exhibit visible-light range bandgaps (1.79~2.47 eV), significantly lower than those of the precursor oxides (2.93~3.53 eV). Urbach energy values (0.295~0.538 eV for composites vs. 0.080~0.129 eV for precursors) further supported the enhanced photocatalytic potential. Photocatalytic activity was evaluated in aqueous medium through decolorization of rhodamine B dye aqueous solutions under irradiation by a 100 W white LED (6500 K). All composites demonstrated superior decolorization efficiencies compared to their respective pristine oxides after 2 h. A brief discussion of the catalytic mechanism was provided, identifying the Al/Fru@Up composite as the most promising candidate for optimization (originally achieving 70.4% decolorization), with the optimized Al/Fru@Up½ variant showing similar performance (73.4%). Adsorption assays were subsequently performed, highlighting numerical approaches for kinetic analysis and suggesting a two-step adsorption mechanism per site. Finally, preliminary theoretical studies were conducted using density functional theory (time-dependent and stationary cases) to investigate the fructose transformation mechanism and to determine the optical properties of 5-hydroxymethylfurfural, a possible key intermediate.

COMMITTEE MEMBERS:
Presidente - 3292567 - EDUARDO HILLMANN WANDERLIND
Externo ao Programa - 1115883 - ANTONIO MARQUES DA SILVA JUNIOR - UFRRJExterno à Instituição - GUILHERME PEREIRA GUEDES - UFF