Study of EDLC supercapacitors for applications in capacitive deionization

• Grant number: 22/07225-7
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Effective date (Start): July 01, 2022
• Effective date (End): June 30, 2026
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Evaldo Jose Corat
• Grantee: Suelem Soares dos Santos
• Host Institution: Instituto Nacional de Pesquisas Espaciais (INPE). Ministério da Ciência, Tecnologia e Inovações (Brasil). São José dos Campos , SP, Brazil
• Associated research grant: 19/18572-7 - New carbon materials: their relevant space, environmental and relevant spin off applications, AP.TEM

Abstract

This project aims to advance the study of high specific capacitance carbon materials and their application as EDLC (Electric Double Layer Capacitance) supercapacitor. Our materials based on exfoliated nanotubes and oxidized graphenes show excellent specific capacitance (on the order of 330F/g) and have a small pseudo-capacitive effect in saline solutions, thus having great feasibility in capacitive deionization desalination. The limitation found is the small volume of material on flat surfaces. In this project, the objective is to study substrates that allow increasing the specific surface area, in particular the use of dense carbon felts and composites containing activated carbon, on which to deposit carbon nanotubes. Such composites should allow an effective increase in surface area, to take greater advantage of the high specific capacitance. The expected benefits are an increase in the deposition area of carbon nanotubes, in a porous three-dimensional structure, an increase in the electrical conductivity of these substrates due to the presence of carbon nanotubes and a high EDLC capacitance, with the contribution of both carbon nanotubes and substrate material. The biggest challenge in these three-dimensional structures is the surface treatment of the nanotubes to promote their effective exfoliation with high specific capacitance. Our studies have already demonstrated that the gaseous, plasma exfoliation methods are more effective than the liquid routes in highly oxidative media. The most effective treatments to obtain high specific capacitance are done with oxygen or hydrogen plasma. Plasma processes are generally superficial and encounter difficulties in porous three-dimensional structures. We will be studying after-discharge attack methods, in which the effectiveness of the ions is less important, but which takes advantage of the high density of reactive radicals. Other etching methods for exfoliating nanotubes are conventional carbon gas activation methods, either with water vapor or CO. The materials thus obtained will be electrochemically tested in saline solutions with different concentrations of NaCl, in order to study their behavior as electrodes for desalination by capacitive deionization. Furthermore, the solution to this important problem of obtaining materials of high specific capacitance in adequate volumes can also be a solution to correlated problems such as support for pseudocapacitive supercapacitors and battery electrodes, among others. (AU)