Synthesis of Biomass-Derived Carbon Induced by Cellular Respiration in Yeast for Supercapacitor Applications.

Because activated carbon is extensively used in supercapacitors, optimization of its precursors and synthetic strategies are crucial. Inspired by the rich sugar content of banana peel waste, which can be transformed through the respiration of yeast into alcohol with the release of CO2 , we developed an environmentally benign and highly efficient process for the production of renewable heteroatom-doped hierarchical porous carbon materials (yeast-treated banana-peel-based carbon, denoted as YBP) without any additional templates or activation agents. The resulting biologically activated carbon was characterized by near-edge X-ray absorption fine-structure spectroscopy, X-ray photoelectron spectroscopy, and other physical methods. The biologically activated carbon achieved a maximum gravimetric specific capacitance of 476 F g-1 in 1 m H2 SO4 electrolyte. Remarkably, with a moderate specific surface area of 1084 m2  g-1 , the as-obtained activated carbon was found to have a high packing density. With enriched pseudocapacitance sites, the YBP symmetric supercapacitor has a high volumetric specific capacitance and energy density (maximum values of 264 F cm-3 and 23.5 Wh L-1 , respectively). The supercapacitor showed superior cyclic stability, with 94 % capacitance retention for voltage values up to 1.6 V after 10 000 cycles, which confirmed the promising application of this supercapacitor in miniature electronic devices.