Biosupercapacitors with minimized Self-Discharge

Conventional self-charging biosupercapacitor (BSC) systems are derived from electron transfer via two redox polymers that adapt the associated potentials and define the open circuit voltage. This process delivers a high-power pulsed output and stable cycling performance. BSCs rely on the simultaneous redox mediation in both electrodes. However, Nernstian BSCs include glucose dehydrogenase and bilirubin oxidase for glucose oxidation and O2 reduction in the bioanode and biocathode, respectively. In such systems, the charge is stored as the difference in the activity ratio of aOs⁺³/aOs⁺² in redox polymer on both electrodes. The activity gradient of the Nernstian BSC abates during discharge. Meanwhile, throughout the recharging or self-charging process, potential changes of both electrodes follow the Nernst equation, via mid-point equilibrium to the non-equilibrium states, by reverting to the Em in the fully discharged mode. Herein, the state-of-the-art with critical features and potential limitations of BSCs are assessed by showing capacitor cell integration between redox polymers, redox-active species, and corresponding Faradaic signals from enzymatic activity based on a potentially limitless source. Thus, using slaughterhouse waste as a model, the intrinsic parameters are emphasized, such as the charging/leakage current ratio, the bioelectrode potential at the equilibrium, and limiting electrode versus capacitance to examine its potential as an energy source.