Development of sustainable microbe-enhanced bio-carbon for supercapacitor applications

Process engineering of biomass residues to develop cost-effective renewable nanomaterials for energy storage with high porosity, good ionic conductivity, and excellent stability is a necessary step toward a circular economy. In this study, we report a sustainable approach to creating bio-based nanoarchitecture from biofuel industry byproducts, i.e., microbe-treated groundnut shells. These carbon nanostructures were explored as electrode materials, demonstrating their potential as high-performance supercapacitors. A morphology investigation revealed that the microbial fortification of biomass acted as a natural porogen, leading to the formation of meso-nanopores with a high specific surface area as well as a high degree of graphitization, as validated by Raman spectroscopy. Galvanostatic charge-discharge curves exhibited quasi-triangular, symmetric shapes, confirming ideal capacitive behavior and high electrochemical reversibility. Electrochemical Impedance studies disclosed negligible IR drop and outstanding electronic conductivity with excellent capacitance performance due to the efficient distribution of electrolyte ions. Carbon nanostructures from spent substrates synthesized from groundnut shells displayed a high specific capacitance of 576 Fg-1. This work offers a practical and evolutionary approach to advancing the development of biomass-based carbons for supercapacitor applications.