Banca de QUALIFICAÇÃO: GUILHERME RIBEIRO PORTUGAL

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : GUILHERME RIBEIRO PORTUGAL
DATA : 14/07/2022
HORA: 14:00
LOCAL: Sala 306 do Bloco B do Campus de Santo André da Universidade Federal do ABC
TÍTULO:

NaTaO3-based heterostructures and thin films for heterogeneous photocatalysis

PÁGINAS: 90
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
SUBÁREA: Física da Matéria Condensada
ESPECIALIDADE: Estruturas Eletrônicas e Propriedades Elétricas de Superfícies; Interf. e Partículas
RESUMO:

Heterogeneous photocatalytic reactions are cited as the most promising solution for current environmental problems such as the depletion of renewable energy resources and air pollution. Such reactions allow the reform of polluting gases such as CO2 and the obtaining of environmentally friendly H2, aiming at its later redirection both for storage and use in a particular application. In the present project, ab initio theoretical methods based on the Density Functional Theory are used to study how the formation of NaTaO3-based heterostructures and thin films may change the structural, electronic, optical, and catalytic properties of this well-known photocatalyst due to the presence of interfaces and surfaces. For heterostructures, the sequential cations replacement in cubic NaNbO3-NaTaO3 superlattices results in an unexpected band gap reduction to values lower than the bulk band gaps, charge separation, interface related absorption peaks nearer to the visible light spectrum, and a better band-edge alignment with water splitting and CO2 photocatalytic potentials. Thereafter, calculations show that a monoclinic NaTaO3-BaBiO3 superlattice with 24 wt.% BaBiO3 also displays most of the above-mentioned properties. Besides, a semiconductor-to-metal transition accompanied by the formation of a high-mobility two-dimensional electron gas (2DEG) confined at the interface is achieved should the number of BaBiO3 layers be increased. When it comes to thin films, we have first explored orthorhombic (100) NaTaO 3 monolayers, aiming at deep insights of the one‐layer limit impact on their physical properties. The monolayer is initially metallic and magnetic, in contrast to its semiconductor non‐magnetic bulk. In‐plane biaxial strain induces a charge disproportionation state in surface Ta atoms, taking the monolayer to an energy minimum through structural, electronic, and magnetic transitions. A monoclinic semiconductor non‐magnetic monolayer is then obtained. Comparisons with multilayered films unveil that such a phenomenon is restricted to the monolayered system. Further hybrid calculations adjust its band gap, revealing anisotropic absorption peaks in the visible light region. The results presented so far not only help to better understand the importance of low-dimensional NaTaO3-based materials for an intrinsic boost of photocatalytic activity but also shed light towards new applications for such few-layer transition-metal-oxides in developing nanoelectronics.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 1309493 - PEDRO ALVES DA SILVA AUTRETO
Membro Titular - Examinador(a) Interno ao Programa - 1282172 - ROBERTO GOMES DE AGUIAR VEIGA
Membro Titular - Examinador(a) Interno ao Programa - 1671298 - RENATO ALTOBELLI ANTUNES
Membro Titular - Examinador(a) Externo ao Programa - 3944999 - ROMARLY FERNANDES DA COSTA
Membro Suplente - Examinador(a) Interno ao Programa - 2218228 - LUANA SUCUPIRA PEDROZA
Membro Suplente - Examinador(a) Externo ao Programa - 1544394 - PAULA HOMEM DE MELLO