Abstract
Nanoporous activated carbon materials derived from agro-wastes could be suitable low-cost electrode materials for high-rate performance electrochemical supercapacitors. Here we report high surface area nanoporous carbon materials derived from Lapsi seed agro-waste prepared by zinc chloride (ZnCl2) activation at 700 °C. Powder X-ray diffraction (pXRD) and Raman scattering confirmed the amorphous structure of the resulting carboniferous materials, which also incorporate oxygen-containing functional groups as confirmed by Fourier transform infrared (FTIR) spectroscopy. Scanning and transmission electron microscopy (SEM and TEM) analyses revealed the granular, nanoporous structures of the materials. High-resolution TEM (HR-TEM) confirmed a graphitic carbon structure containing interconnected mesopores. Surface areas and pore volumes of the materials were found, respectively, in the ranges from 931 to 2272 m2 g−1 and 0.998 to 2.845 cm3 g−1, and are thus superior to commercially available activated carbons. High surface areas, large pore volumes and interconnected mesopore structures of these Lapsi seed-derived nanoporous carbon materials lead to their excellent electrochemical supercapacitance performance in aqueous electrolyte (1 M H2SO4) with a maximum specific capacitance of 284 F g−1 at a current density of 1 A g−1. Furthermore, the electrodes showed high-rate capability sustaining 67.7% capacity retention even at high current density of 20 A g−1 with excellent cycle stability achieving 99% capacitance retention even after 10,000 charge–discharge cycles demonstrating the potential of Lapsi seed derived nanoporous carbons as suitable electrode materials in high-performance supercapacitor devices.
Highlights
Ultracapacitors or electrical double-layer capacitors (EDLCs) are of substantial technological interest since they provide improvements in operation over the poor cycle stabilities and low power densities of conventional rechargeable batteries [1,2,3,4,5]
Previous investigations have shown that specific capacitance of an electrode material is correlated directly with its surface textural properties including specific surface area, pore volume, interconnectedness of pores and the conductivity of the materials indicating the importance of the design of the electrode materials [19,20]
We report the facile fabrication of very high surface area nanoporous activated carbon materials from Lapsi seed agro-waste by the ZnCl2 activation method, and their use as electrode materials for high-rate performance supercapacitors in aqueous electrolyte
Summary
Ultracapacitors or electrical double-layer capacitors (EDLCs) are of substantial technological interest since they provide improvements in operation over the poor cycle stabilities and low power densities of conventional rechargeable batteries [1,2,3,4,5]. The interconnected mesoporous network structures with open pores of biomass-derived nanocarbon materials with three-dimensional (3D) architecture obtained by an activation process offer easy access for the guest ions to their interiors increasing the charge storage capacity of the materials by increasing the effective surface area accessible to the electrolyte ions While activating agents such sulfuric acid, phosphoric acid, potassium hydroxide, or potassium carbonate have been used, zinc chloride (ZnCl2) is one of the most extensively used agents for the chemical activation of a carbonaceous material [55,56,57]. The optimal sample displayed a specific surface area about 1000 m2 g−1 and the material showed excellent dye adsorption properties In this contribution, we report the facile fabrication of very high surface area nanoporous activated carbon materials from Lapsi seed agro-waste by the ZnCl2 activation method, and their use as electrode materials for high-rate performance supercapacitors in aqueous electrolyte. This work demonstrates utilization of biomass for the production of excellent electrode materials for high-performance supercapacitor devices
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