Viability of Activated Carbon Derived from Polystyrene Sulphonate Beads as Electrical Double Layer Capacitors

Gbenro Babajide Folaranmi,Anthony Ekennia,Nkiruka Chidiebere Ani,Richard Chukwuemeka Ehiri

doi:10.3390/c7040082

Abstract

In this paper, a commercial polymeric resin precursor (polystyrene sulphonate beads) was used as a source of carbon spheres. The resin was pyrolyzed at different temperatures (700, 800, and 900 °C) and the resulting carbons were analyzed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). From the result of EIS, carbon spheres obtained at 700 °C (CS−700) have the least ohmnic resistance and highest capacitance. In furtherance, the resin was chemically activated with iron (III) chloride FeCl3·6H2O at different concentration (0.1 M, 0.3 M, and 0.5 M) and pyrolyzed at 700 °C to obtain activated carbon sphere namely (ACS 700−0.1, ACS 700−0.3, and ACS 700−0.5) in which the last digit of the samples denotes the concentration of FeCl3. Scanning electron microscope (SEM) showed that the carbon is of spherical shape; X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and X-ray photon electron spectroscopy (XPS) revealed successful introduction of Fe on the surface of the carbon. Out of all the activated carbon spheres, ACS 700−0.1 exhibited highest double layer capacitance of 9 µF cm−2 and lowest charge transfer resistance of 3.33 KΩ·cm2. This method shows that carbon spheres obtained from a polymeric source can be easily improved by simple resin modification and the carbon could be a potential candidate for an electrical double layer capacitor.

Highlights

The field of electrochemical capacitors, with a focus on electrical double layer capacitors (EDLCs), is becoming increasingly popular in our day
As a result of this, we studied the pyrolytic conditions and electrochemical behavior of carbon generated from this commercial polymeric-based precursor through chemical modification of the polymer followed by pyrolysis at various temperatures
Carbon spheres synthesized at 700 ◦ C had the best electrochemical characteristics and the most spherical form of all the carbon spheres tested

Summary

Introduction

The field of electrochemical capacitors, with a focus on electrical double layer capacitors (EDLCs), is becoming increasingly popular in our day. The ion storage mechanism of a supercapacitor/pseudo-capacitor is based on the Faradaic redox process [2], whereas the ion storage mechanism of an EDLC is based on a non-redox process (adsorption process) [3]. Both types of capacitors work on the same principle: two sandwiched electrodes are sandwiched in an electrolyte and set parallel to each other. Because of their porosity, high surface area, and adsorption capabilities, carbon-based materials have been widely explored as capacitor sources [7,8]. On the other hand, has some downsides—such as low hydrophilicity, low capacitance, and low conductivity, to name a few [9]—and as a result, techniques to overcome these shortcomings have been the focus of recent research

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