Abstract
Polyimide-graphene nanosheet composite electrodes are rigid and dense and, therefore, exhibit moderate electrochemical properties. The electrochemical properties of polyimide-graphene nanosheet electrodes were remarkably improved by creating voids in the composite followed by the insertion of nickel oxide into the composites. Nickel oxide particles were electrodeposited onto the porous graphene/poly(amic acid) composite, containing poly (acrylic resin). The hybrid composite was then subjected to thermal treatment at ≥ 300 °C to simultaneously complete imidization and degrade the poly (acrylic resin). Cyclic Voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to study the eletrochemical properties of the composite electrode material. It is shown that remarkable improvement in the electrochemical behavior of the hybrid composite occurred due to the removal of poly(acrylic acid) and the insertion of NiO particles into the polyimide matrix. Fourier Transform Infrared Spectroscopy (FTIR) spectra of the hybrid composites show distinct characteristic peaks for polyimide and NiO in the hybrid composite electrode. Scanning Electron Microscopy, SEM images of the composites, show the presence of NiO aggregates in the composite material. Compared to neat graphene/polyimide composite electrode (GR/PI) composites, the specific capacitance of the hybrid composite electrode increased remarkably by over 250% due to the high interfacial surface area provided by NiO and the concomitant improvement in the electrode–electrolyte interaction.
Highlights
Electrochemical capacitors have generated much interest as energy storage devices due to their instantaneous power output and excellent charge/discharge capabilities
Compared to neat graphene/polyimide composite electrode (GR/PI) composites, the specific capacitance of the hybrid composite electrode increased remarkably by over 250%
The specific capacitance obtained from Cyclic Voltammetry (CV) measurement of neat GR/PI
Summary
Electrochemical capacitors have generated much interest as energy storage devices due to their instantaneous power output and excellent charge/discharge capabilities. Carbon-based materials, such as activated carbon, carbon nanotube (CNT) and graphene, are used in super-capacitor design due to their high electric double layer capacitances. Other materials, such as conducting polymers and transition metal oxides, such as ruthenium oxide, manganese oxide, cobalt oxide and nickel oxide, find application in design because they demonstrate excellent Faradaic charge transfer mechanisms that yield excellent pseudo-capacitance values as high as 1200 F/g. Graphene–polymer composites have found particular interest in this space because of the ease of graphene dispersion in most polymers [1,2,3,4] Such composites possess both excellent mechanical and thermal stability and they are attractive for use in flexible standalone electrodes. Graphene/polyimide (GR/PI) composites are currently being studied by our
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