A membrane-less Zn-air biobattery/supercapacitor hybrid device

We report herein a membrane-less biobattery/supercapacitor hybrid by incorporating a bilirubin oxidase (BOD) based biocathode undergoing direct electron transfer (DET) with a robust zinc anode. The biobattery itself registers a maximum power density of 304.3 +/- 7.0 mu W cm -2 and an open-circuit voltage of 1.61 +/- 0.1 V. When operated as a self-charging supercapacitor, it exhibits an impressive six-fold increase in power density compared to the standalone biobattery, and generates electrical pulses over 500 cycles with around 92 % of the initial power density retained. Another major finding is the better operational stability of the hybrid device over the biobattery alone due to the incorporation of biosupercapacitor, which is likely due to the less produced H 2 O 2 .