Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


22322.pdf (9.42 MB)

ETD Abstract Container

Abstract Header

Processing and Characterization of Graphene/Polyimide-Nickel Oxide Hybrid Nanocomposites for Advanced Energy Storage in Supercapacitor Applications

Okafor, Patricia A.
http://orcid.org/0000-0002-1831-023X
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823253057854

Abstract Details

2016, PhD, University of Cincinnati, Engineering and Applied Science: Materials Science.
This research is focused on enhancing electrochemical properties/energy storage capabilities of graphene-polyimide composites. The composite’s dense morphology/structure limits ionic penetration owing to high bulk resistances resulting in poor electrochemical performance. Modification of the composite’s morphology by incorporation of facile pores during curing increases total available surface area to electrolyte species. Presence of pores increases adsorption sites for double layer formation and increases overall capacitance. In this work, aromatic polyimide precursors were reacted in the presence of nano-graphene fillers to synthesize graphene–polyimide composite films. The resulting composite was very stiff and dense with a high glass transition temperature (Tg) of ~ 400 oC and storage modulus of 7.20 GPa. Selective decomposition of a thermally labile poly(acrylic ester) resin introduced into the composite during synthesis creates pores of varying size and shapes which increases available surface area of embedded stacked graphene sheets available for ion adsorption and double layer formation. Proper control over pore size and specific surface area of pores was required to ensure good performance in terms of both power delivery rate and energy storage capacity. Dynamic mechanical studies on modified composite showed very good mechanical property while shifts in imide peaks to lower wave numbers in Raman and Fourier transform spectroscopy (FTIR) confirms presence of chemical interaction between graphene filler and polymer matrix confirming uniform dispersion of fillers in the material. Thermogravimetric analysis (TGA) shows thermal stability for the composite systems at temperatures above 700oC. To further optimize material’s energy storage capabilities, a hybrid composite was formed by depositing relatively cheap nickel oxide onto the modified porous composite system by a two-step process. A remarkable improvement in electrochemical properties up to an order of magnitude was observed. Electrochemical performance of the hybrid system showed strong dependence on deposition current density, deposition time and substrate pore morphology. Increased NiO particle size (aggregates) was observed with increased deposition time and current density which had a significant impact on charge transfer resistance and specific capacitance. Several correlations were made between composite’s morphology and obtained properties. The material’s morphology showed direct correlation with double layer capacitance, charge capacity, bulk resistance and sheet conductivity measured using cyclic voltammetry (CV), cyclic charge discharge (CCD), electrochemical impedance spectroscopy (EIS) and four probe measurements respectively. It was observed that smaller well distributed pores showed enhanced properties compared to larger pores. Material’s overall performance shows a linear dependence on porosity. The overall electrochemical and electrical behavior of the system is directly linked to the composite’s morphology and structure as will be demonstrated in this thesis work.
Jude Iroh, Ph.D. (Committee Chair)
Gregory Beaucage, Ph.D. (Committee Member)
Rodney Roseman, Ph.D. (Committee Member)
Dale Schaefer, Ph.D. (Committee Member)
261 p.
Materials Science
Graphene; Polymer composites; Nickel oxide; Supercapacitor; Energy; Energy storage

Recommended Citations

Citations

  • Okafor, P. A. (2016). Processing and Characterization of Graphene/Polyimide-Nickel Oxide Hybrid Nanocomposites for Advanced Energy Storage in Supercapacitor Applications [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823253057854

    APA Style (7th edition)

  • Okafor, Patricia. Processing and Characterization of Graphene/Polyimide-Nickel Oxide Hybrid Nanocomposites for Advanced Energy Storage in Supercapacitor Applications. 2016. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823253057854.

    MLA Style (8th edition)

  • Okafor, Patricia. "Processing and Characterization of Graphene/Polyimide-Nickel Oxide Hybrid Nanocomposites for Advanced Energy Storage in Supercapacitor Applications." Doctoral dissertation, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823253057854

    Chicago Manual of Style (17th edition)

ucin1479823253057854
506
© 2016, some rights reserved.Creative Commons License Processing and Characterization of Graphene/Polyimide-Nickel Oxide Hybrid Nanocomposites for Advanced Energy Storage in Supercapacitor Applications by Patricia A. Okafor is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.