D. Shrestha1, S. Maensiri2, S. W. Lee3, A. Rajbhandari (Nyachhyon)*4
1, 4Patan Multiple Campus, Tribhuvan University, Patandhoka, Lalitpur, Nepal
2School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, 30000 Thailand
3Research Centre for Eco Multi-Functional Nano Materials, Global Research Laboratory (GRL), Sun Moon University, Asan-si, Chungnam 31460, South Korea
4Central Department of Chemistry, Tribhuvan University, Kirtipur, Kathmandu, Nepal
A B S T R A C T
This paper reports the preparation of nanoporous activated carbons by carbonizing sawdust of Shorea robusta which belongs to the family- Dipterocarpaecea and is commonly called Sal. Three different activating agents namely H3PO4, KOH and Na2CO3 has been used in the ratio of 1:1 (wt:wt) to activate carbon samples and was named as(Sa-H3PO4-4S), (Sa-KOH-4S) and(Sa-Na2CO3-4S). Samples were characterized by TGA/DSC, XRD, FTIR. All the carbon samples were found to be amorphous in nature. The oxygen surface functionality were developed at the surface. The surface area of (Sa-H3PO4-4S), (Sa-KOH-4S) and (Sa-Na2CO3-4S) were found to be 1269.5 m2g-1, 280.6 m2g-1 and 58.9 m2g-1 respectively. The carbon-electrodes were then fabricated and super capacitive performance were evaluated by “three electrode system” in aqueous 6M KOH using cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS).The excellent specific capacitance acquired from GCD at 1Ag-1 were 136.3 Fg-1, 42.2 Fg-1 and 59.1 Fg-1 for the samples Sa-H3PO4-4S, Sa-KOH-4S and Sa-Na2CO3-4S, respectively. Energy density for Sa-H3PO4-4S electrode was found to be 3.0 Whkg-1 at 99.6 Wkg-1 power density which was significantly higher than reported value of 9.4 Whkg-1. Moreover, it also displayed imposing cycling life stability of about 96.9%, 89.5% and 78.5% after 1000 cycles of charge/discharge respectively. The overall electrochemical performance of Sa-H3PO4-4S showed outstanding supercapacitive performance demonstrating the high possibility of this material to be used for the EDLC application in supercapacitive energy storage. The Nyquist plot also showed the lowest internal resistance of about 0.4W for Sa-H3PO4-4S electrode which was lower than other two carbon electrodes namely Sa-KOH-4S and Sa-Na2CO3-4S.
Keywords: Shorea robusta, Specific capacitance, Energy density, Power density, cycling life stability