Omer Sadak
Published: 2019
Total Pages: 0
Get eBook
Graphene (Gr) and its derivatives have ignited tremendous research interest for a wide range of applications in the fields of electricity, energy generation and storage, sensors, water purification, medicine and more due to their superior properties. Gr can be prepared from graphite in many ways: mechanical cleavage, chemical exfoliation, thermal decomposition, or electrochemical exfoliation. Among these, electrochemical exfoliation, which is performed without the use of toxic, corrosive oxidizing/reducing agents, is a simple, rapid, and green method to produce graphene flakes. By taking advantage of their unique properties, electrochemically exfoliated graphene (EG)-based nanomaterials were fabricated for energy applications, specifically to be used in supercapacitor. A free-standing, highly flexible and conductive graphene paper (GrP) was fabricated via a simple, green, and inexpensive method. The fabrication process starts with electrochemical exfoliation of graphite as partially oxidized graphene suspension, which is then vacuum-filtered and air-dried. The thickness of GrP is controlled by adjusting the volume and/or concentration of partially oxidized graphene suspension used for filtration. The procedure does not warrant any binders, toxic and corrosive agents, or high temperature compared to common methods for fabrication of paper-like graphene platforms. The GrP possesses excellent mechanical and electrical properties. and electrochemical characteristics. When used as electrodes in supercapacitor, GrP has superior capacitance retention compared to other paper-like Gr materials reported in the literature. Moreover, the GrP is an excellent absorbent of oils and organic solvents and is reusable. Therefore, this environmentally friendly GrP fabrication method can be used for large-scale fabrication for applications such as energy-storage devices, flexible/wearable electronics, and removal of oil or toxic organic spills (Chapter II). IV To improve the capacitance behavior of GrP, a pseudocapacitive material, manganese dioxide (MnO2), was electrochemically deposited on GrP with different number of MnO2 cycles. After electrochemical deposition process, MnO2 nanoflowers were formed, which enhanced transfer of electrolyte ions. After 10 cycles of electrodeposition, MnO2-coated GrP (GrP/10-MnO2) electrode exhibited an excellent capacitive performance and outstanding cyclic stability. Flexible solid-state supercapacitor made of GrP (negative electrode) and GrP/10-MnO2 (positive electrode) was tested, which showed outstanding capacitance behavior (Chapter III). A facile strategy for the fabrication of EG intercalated with polyaniline (PANI) via one-step interfacial polymerization technique on a heterogeneous biphasic system under acidic condition was studied. EG and the PANI formed a uniform nanocomposite with PANI nanoparticles grafted on the EG surface. The EG-PANI nanocomposite exhibited a high specific capacitance and good capacity retention after 1000 galvanostatic charge-discharge cycles. A solid-state asymmetrical supercapacitor device was fabricated using EG (negative electrode) and EG-PANI (positive electrode), to demonstrate its energy storage application (Chapter IV).