**1. Introduction**

With climate change and environmental concern, new energy sources have been created and various advanced energy storage systems. They simultaneously possess high energy and high power density as well as excellent recyclability, low cost, and friendly to the environment [1].

There are energy storage devices such as lithium-ion batteries often possessing high energy (200 Wh/Kg) but relatively low power density (1 KW/Kg), while traditional electrostatic capacitor has high power (40 KW/Kg) but low energy density (0.03 Wh/Kg) [2]. However, the electrochemical capacitor is a new type of high power and high energy density storage and deliverance device, therefore promising for feeding a variety of equipment operating with energy [3].

The capacitors can be divided into two classes based on charge-storage mechanism: (a) electrical double layer capacitors (EDLCs), where in electrode/electrolyte system, direction arrangement of the electron, or ion at the electrode/electrolyte interface forms electrical double layer [4] and (b) pseudo-capacitors, where the pseudo-capacitance arises from Faradaic reactions taking place at the electrode/electrolyte interface [5].

**2. Methodology development**

polyaniline, and the incorporation of AuNp on the matrix GO/PANI.

**2.2. Synthesis of graphene oxide sheets**

(5 g), and concentrated H<sup>2</sup>

**2.1. Materials**

(KMnO<sup>4</sup>

(30% H<sup>2</sup>

NaNO3

H2 O2 O2

The systems discussed were synthesized by the methodology, as shown in **Figure 1**, in which

**Figure 1.** In situ polymerization of graphene oxide with polyaniline, forming the hybrid composite graphene oxide/

Synthesis and Characterization of Reduced Graphene Oxide/Polyaniline/Au Nanoparticles…

) from Meyer. Aniline monomer and gold (III) chloride trihydrate (HAuCl<sup>4</sup>

polytetrafluoroethylene (PTFE) were purchased from Sigma Aldrich. The hydrogen peroxide

Graphite oxide (GO) was synthesized by a modified Hummer's method [11]. Graphite (10 g),

over the stirring mixture, the temperature was controlled below 35°C, and the whole mixture was stirred for 2 h. After 30-min rest, the temperature of the mixture was raised to 98°C, and

After 30 min, the mixture was diluted by 1.4 l of de-ionized water and treated with (25 ml)

Polyaniline was synthesized by chemical polymerization using ammonium persulfate (APS) as oxidant and HCl as doping agent. The aniline and APS mole ratio employed was 1:1, dissolved

 30% to reduce residual permanganate to soluble manganese ions until the gas evolution ceased. The resulting suspension was washed with HCl 1 M and de-ionized water until the filtrate became neutral and remaining impurities were removed. The product, graphite oxide,

) was purchased from Reasol, and ammonium persulfate (APS) was from Golden Bell.

SO<sup>4</sup>

·H<sup>2</sup>

), and potassium permanganate

http://dx.doi.org/10.5772/intechopen.77385

77

(30 g) was added gradually

(230 ml) were mixed and stirred at 0°C in a 2000 ml

), hydro-

O) and

steps are described later and using the specified precursors and solvents.

SO<sup>4</sup>

460 ml of de-ionized water was slowly added to the suspension during 40 min.

was exfoliated in an ultrasonic bath (2 h) to form graphene oxide (GO) sheets.

**2.3. Synthesis of polyaniline nanofibers and in situ polymerization GO/PANI**

reaction flask, which was immersed in an ice bath. Then, KMnO<sup>4</sup>

chloric acid (HCl), acetone, ethanol 98%, sodium nitrate (NaNO<sup>3</sup>

All reactives were analytic degree: natural graphite powder, sulfuric acid 98% (H<sup>2</sup>

From the basic characteristics that determine the development of high-performance electrochemical capacitor (EC) electrodes, the most important are design, manufacture electrodes with suitable materials, architecture, and structure [2].

The typical electrode materials for EDLC are carbon materials (carbon nanotubes, graphene, activated carbon, etc.) due to their high-specific surface area and excellent conductivity [6], and the conductive polymers (polypyrrole, polyaniline, and polythiophene) are often used for pseudo-capacitors due to their high conductivity and large storage capacity [7]. However, the specific capacitance of carbon materials is commonly far less than that of conductive polymers, and the storage capacity of conductive polymers gradually decreases with the increase in the number of cycle (charge-discharge) [4].

In order to alleviate the inherent drawback of single materials, researchers have combined carbon materials and conductive polymers to obtain hybrid or composite materials with both high-specific capacitance and good cycle life called hybrid supercapacitors [8].

There are two methods for the preparation of hybrid capacitors: chemical methods in which an oxidizing agent is used and in-situ polymerization occurs, e.g., in situ chemical polymerization of graphene with polyaniline [9], forming the hybrid composite graphene/polyaniline (**Figure 1**). Another method is the electrochemical synthesis of conductive polymeric nanocomposites in which nanomaterials are dispersed in a monomer solution and formed by electropolymerization [10].

Being Au an excellent conductive material, it can be used to improve further the electrical properties of the GO/PANI hybrid material, incorporating it into the polymer matrix, as gold nanoparticles (NpAu), expecting the nanoscale dimension to potentiate the overall hybrid material properties.

With all the above ideas in mind, the next section shows some results about the synthesis of graphene oxide/polyaniline/Au nanoparticles hybrid material suitable to be used for energy applications.

Synthesis and Characterization of Reduced Graphene Oxide/Polyaniline/Au Nanoparticles… http://dx.doi.org/10.5772/intechopen.77385 77

**Figure 1.** In situ polymerization of graphene oxide with polyaniline, forming the hybrid composite graphene oxide/ polyaniline, and the incorporation of AuNp on the matrix GO/PANI.
