Chika Anthony Okonkwo
Xiamen University, China
Title: Salt encapsulated sand template for mesoporous honeycomb-shape carbon synthesis from castor seed shell and improvement of super capacitor
Biography
Biography: Chika Anthony Okonkwo
Abstract
Statement of the Problem: High ions storage target for supercapacitors still suffer from limited mesopores which hampers accommodation of most ionic sizes and also slows competitive/huge commercialization of electrochemical double layer capacitors especially where high power and rapid responses are necessary. Mesopores as indispensable factor of high ions storage, attract many diverse materials in researches over decades for this reason to improve specific capacitance and directly obtain high energy and power densities. Carbonaceous materials or its composites have shown that due to inherent/intrinsic adjustable property, mesopores are high predictable in carbon materials especially in variable shape/structural forms which usually improve by activation with potassium hydroxide (KOH). However, dual shape/structure by simple cost-effective preparation method (salt encapsulated sand template) has not been previously studied. This study centers on describing the interstice/ intramesopores dual form in a systematic steps sand induces surface roughness which metamorphous into honeycomb-shape/flakes carbon.
Methodology & Th eoretical Orientation: Typical acid anhydrous decomposition was employed to produce silicon carbide particles from the sand to induce rough surface on carbon flakes during the castor seed shell break down. The residual acid in the carbon was deprotonated by hydrothermal process to prevent acid salt formation in the presence of potassium hydroxide during activation process and also to reduce the formation of water molecules that may inhibit anhydrous KOH activation of the carbon. Imperative porosity characterization, structural/functional group investigation, and fundamental shape morphology were conducted to compare the two major samples. Conventional graphite symmetric electrodes were prepared as electrochemical double layer capacitors in 6 M KOH electrolyte.
Findings: The interstice / intra-mesopores mixture consists of high specific surface area of fl akes and honeycomb-shape carbon required to boast the mesopores porosity. N2 adsorption-desorption curve shows type IV isotherm to confirm the presence of mesopores, wherefore related dV/dD particle distribution shows predominating mesopores range (2–50 nm) inset. Energy transmittance across the sample molecules shows effect of dual molecular related shapes of carbon consistently across the FTIR spectra. Oxygen-containing functional groups content satisfi es the conditions for surface wettability and enhancement of ions transfer rate as represented in XPS chemical state. As supercapacitors electrode, the superior sample exhibited high specific capacitance (481 Fg-1) in 6 M KOH as electrolyte. Almost no decay occurred aft er charging/discharging test of 15000 cycles and the capacitance retention remains 96 %.
Conclusion & signifi cance: Indeed the degree of improvement in this study really shows that ions storage largely depends on mesopores to make high specific capacitance in the right context of better carbonaceous materials. This template decomposition of castor seed shell is quite promising, however more organic carbonaceous or composites are necessarily good approach to achieving the expectancy of ultra-high specifi c capacitance of supercapacitors.