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Construction and electrochemical characterization of grapheme-based electrodes

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Author(s):
Lucas Lodovico de Carvalho
Total Authors: 1
Document type: Master's Dissertation
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
Defense date:
Examining board members:
Roberto Manuel Torresi; Fabio Henrique Barros de Lima; Paulo Teng An Sumodjo
Advisor: Roberto Manuel Torresi
Abstract

The increasing demand for efficient electrical energy storage devices has pushed research towards materials with potential to increase the specific performance of such devices. Among the carbon-based materials, one that has been heavily studied as a potential candidate to accomplish such feat is graphene and its chemical derivatives. In this work, two methodologies to accomplish graphene immobilization over metallic current collectors are approached, as well as the effects that such approaches have on the electrochemistry of the resulting electrodes. As a general guideline, the usage of polymeric binders as ways of keeping good mechanical stability are avoided, due to their tendency to negatively impact the system\'s electrochemistry (not only they\'re normally electrical in sulators, they also don\'t usually possess any intrinsic electroactivity that could enhance the electrode\'s capacitance). The methodologies in study can be separated into two categories, namely, electrophoretic deposition and usage of organic molecules as anchoring points to attach graphene sheets to the surface. Such electrodes were characterized by a number of electrochemical technics, most prominently cyclic voltammetry and electrochemical impedance spectroscopy in the group of electrochemical technics, and Raman spectroscopy, atomic force microscopy, scanning electron microscopy and quartz crystal microbalance in the group of non-electrochemical technics. Electrophoretic deposition of graphene is proved to be a very straightforward and reproducible way to obtain modified electrodes. Since no chemical compound other than the graphene derivatives are necessary, and that the final electrodes have very rough surfaces, such electrodes have very high capacitance, and those characteristics are direct consequence of the chosen method. Anchoring graphene derivatives on the surface of metallic conductors by the (electro)-chemistry of diazonium salts is shown to be a promising method to achieve strongly bound graphene sheets to a surface. The high reactivity of diazonium salts, though, hampers the electrochemical activity of graphene, and no electrodes suitable to be used in electrochemical capacitors were obtained. In summary, the advances and remaining challenges towards the use of such methodologies in the construction of electrochemical capacitors are presented here. (AU)

FAPESP's process: 11/16078-3 - Graphene electrochemistry in ionic liquids
Grantee:Lucas Lodovico de Carvalho
Support Opportunities: Scholarships in Brazil - Master