Banca de DEFESA: DENIS FERNANDO ALVARENGA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : DENIS FERNANDO ALVARENGA
DATE: 29/09/2021
TIME: 10:30
LOCAL: Plataforma RNP
TITLE:

DEVELOPMENT OF FLEXIBLE ELECTRODES OF CARBON NANOTUBE/CELLULOSE NANOFIBRILS FOR APPLICATION IN REDOX SUPERCAPACITORS

KEY WORDS:

Supercapacitors; Buckypapers; Cellulose nanofibrils; Carbon nanotubes; Redox electrolytes.

PAGES: 101
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Físico-Química
SPECIALTY: Eletroquímica
SUMMARY:

Currently, supercapacitors (SCs) stand out for being energy storage devices with high-power density. However, to maximize its niche of applications, many efforts have been made to increase its energy density compared to batteries and fuel cells. Furthermore, with the growing demand for miniaturized, thin and flexible electronic devices, the development of electrode materials that meet these characteristics is necessary. In this work, thin and flexible electrodes were developed, called buckypapers (BPs), composed of carbon nanotubes/cellulose nanofibrils (CNT/CNF), in a 1:1 mass ratio, for application in redox SCs. The CNFs used, α-CNFs, β-CNFs and γ-CNFs, were obtained, respectively, from three different cellulosic matrices: Eucaliptus sp, Pinus sp and Bambusa vulgaris. The incorporation of these low cost and biodegradable cellulosic components was carried out to optimize the mechanical and surface properties of BPs. The films were also evaluated for their morphological, thermal and electrical properties. As a result, all BPs showed thermal stability up to 132 ºC, electrical conductivity greater than 0.15 S cm^-1 and an increase of 125% in tensile strength and 67% in maximum tensile strength, compared to a BP/without cellulose used as reference. Finally, the BPs were analyzed as redox SCs electrodes in two media: one of them an alkaline medium containing the redox additive potassium hexacyanoferrate(II) (0.1 M K₄[Fe(CN)₆] in 3.0 M KOH) and the other, an acidic medium containing methylene blue AM as an additive (0.07 M AM in 1.0 M H₂SO₄). All BPs, α-BP, β-BP and γ-BP, prepared with the different CNFs are stable in acid and basic electrolytes and mediate electron transfer from redox additives. The cell constructed with γ-BP immersed in alkaline redox electrolyte stands out with a specific capacitance (at electrode level) of 167.64 F g^-1 (a 5 mA), with a capacitance retention of 98.15% after 12000 galvanostatic charge/discharge cycles. Using the acid redox electrolyte, the best performance in terms of specific capacitance was obtained for α-BP (40.85 F g^-1 to 5 mA), with 80.53% capacitance retention after 12000 cycles.

BANKING MEMBERS:
Presidente - PAULO FERNANDO RIBEIRO ORTEGA
Interno - EUDES LORENCON
Externo ao Programa - MARIO GUIMARAES JUNIOR
Externo à Instituição - GARBAS ANACLETO DOS SANTOS JUNIOR - UFV