Activated carbon from banyan prop root biomass and its application in pseudocapacitors: a strategy towards circular economy for energy

Abstract

We project banyan prop root biomass waste as an alternative zero-cost precursor for preparing activated carbon for fabricating electrodes for pseudocapacitors. Banyan prop root activated carbon (BPRAC) powder was obtained by activating the dried biomass powder in concentrated H2SO4 followed by thermal processing at 800 °C under N2 atmosphere for 1 h. Relevant physical characterization studies were done on BPRAC to assess its quality prior to examining the capacitive output in 1 M H2SO4 (acid) and 1 M Na2SO4 (neutral) electrolytes by impedance spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge cycling studies. The specific capacitance calculated by cyclic voltammetry in acid electrolyte is as high as 466 F/g at a scan rate of 10 mV/s. Significant electrochemical stability with 91% of the initial capacitance is retained at the end of the 500th cycle. Practical and acceptable electrochemical output (pseudocapacitance) that is tapped from BPRAC is presumed to be built upon certain favorable physical features like surface organic functional groups containing heteroatoms on the BPRAC. Thus, the ascendancy of waste biomass in energy storage devices provides a strategy for both recycling of wastes and eco-friendly capacitor electrodes.