Nitrogen-rich green leaves of papaya and: Coccinia grandis as precursors of activated carbon and their electrochemical properties

Dulyaseree, Paweena; Fujishige, Masatsugu; Yoshida, Ichiro; Toya, Yumiko; Banba, Yasuo; Tanaka, Yu Suke; Aoyama, Takaaki; Phonyiem, Mayuree; Wongwiriyapan, Winadda; Takeuchi, Kenji; Endo, Morinobu

doi:10.1039/c7ra06048c

Nitrogen-rich green leaves of papaya and: Coccinia grandis as precursors of activated carbon and their electrochemical properties

Author(s)

Dulyaseree, Paweena

Fujishige, Masatsugu

Yoshida, Ichiro

Toya, Yumiko

Banba, Yasuo

Tanaka, Yu Suke

Aoyama, Takaaki

Phonyiem, Mayuree

Wongwiriyapan, Winadda

Takeuchi, Kenji

Endo, Morinobu

Date Issued

January 1, 2017

Type

Article

DOI

10.1039/c7ra06048c

Abstract

Activated carbon (AC) was synthesized from papaya and Coccinia grandis leaves (PL-AC and CL-AC, respectively) which are nitrogen-rich precursors and their electrochemical properties were investigated. The synthesis process included carbonization at 400 °C, impurity removal by H2SO4 cleaning, and post activation by NaOH at 720 °C. Surpassing the conventional bamboo-derived AC (B-AC), PL- and CL-ACs show relatively high surface areas of 2664 and 2576 m² g^-1, respectively. Moreover, the nitrogen contents in the PL- and CL-ACs were approximately 2.3 and 1.8 at%, respectively. Furthermore, the electrochemical properties of the synthesized PL- and CL-ACs were investigated using both aqueous and organic electrolytes. The specific capacitances of the PL- and CL-ACs were 98.47 and 89.91 F g^-1, respectively, in Na2SO4 electrolyte. Especially, compared to the B-AC, the PL-AC shows a dramatic decrease in series resistances (RS) from 1.33 to 0.53 Ω and charge transfer resistances (RCT) from 25.83 to 9.00 Ω. The decrease of RS and RCT is attributed to the existence of nitrogen in the PL-AC, resulting in a higher conductivity of electrode material and an enhancement of the charge transfer between electrode material and electrolyte. The large surface area of the PL- and CL-ACs was successfully achieved without detriment to the electrical conductivity. These results suggest that nitrogen-rich PL and CL are potential precursors for the synthesis of nitrogen-doped AC in a one-step process, which can be used as an alternative electrode material for electrochemical capacitors and can potentially be applied for large-scale industrial production with low cost.

Citation

Rsc Advances, 7(67), 42064-42072, 2017