Unleashing Moisture Content as a Capacitance Deciding Factor for Supercapacitors derived from Wild Orchid

All carbonaceous materials manifest Electrical double layered capacitor (EDLC) type behaviour. Still, drawbacks like cost-effectiveness and availability of precursor materials provide a spotlight on “Biomass derived carbons” as electrode material for supercapacitors. Nevertheless, different types of biomasses show uniqueness in their properties and thus reveal differences in carbon materials derived from them. During carbonizing or pyrolysis of biomass, a factor called moisture is generally ignored or removed by simply drying the sample in an air oven. Here in this work, we choose leaves of a wild orchid (Vanda Tasselleta) which is an abundantly available species of plant from the Indian subcontinent to Indochina, to establish a relation between moisture content in biomass, rate capability and capacitance of electrode material. Interestingly out of five variations viz normal leaves without treatment, dried leaves, soaked leaves, a mixture of dried and normal leaves, and -20 ⁰C samples, carbon derived from normal leaves shows the highest capacitance of 213.43 F/g at 0.5 A/g without any activation. But fascinatingly normal leaves without treatment show the lowest rate capability of only 35.53 % which is approximately half of the rate capability obtained for dry leaves of wild orchids exhibiting 124.78 F/g capacitance at 0.5 A/g. Moreover, our work demonstrates the dependence of pore size distribution on the amount of moisture intact in wild orchid leaves with the help of characterization techniques. Finally, a two-electrode symmetric device was fabricated showing high capacitance and capacitance retention which shows practical application of wild orchid leaves as supercapacitor electrode material.