Introducing pseudo-capacitive bioelectrodes into a biofuel cell / biosupercapacitor hybrid device for optimized open circuit voltage

International audienceWe report the fabrication of a polymer/enzyme based biosupercapacitor (BSC)/biofuel cell (BFC) hybrid device with optimized cell voltage that can be switched on demand from energy conversion to energy storage mode. The redox polymer matrices used for the immobilization of the biocatalyst at the bioanode and biocathode act simultaneously as electron relays between the integrated redox enzymes and the electrode surface (BFC) and as pseudo-capacitive charge storing elements (BSC). Moreover, due to the self-charging effect based on the continuously proceeding enzy-matic reaction, a Nernstian-shift in the pseudo-capacitive elements, i.e. in the redox polymers, at the individual bioelectrodes leads to a maximized open circuit voltage of the device in both operating modes. Comparison with a conventional fuel cell design, i.e. using redox mediators with redox potentials that are close to the potentials of the used redox proteins, indicates that the novel hybrid device shows a similar voltage output. Moreover, our results demonstrate that the conventional design criteria commonly used for the development of redox polymers for the use in biofuel cells have to be extended by considering the effect of a Nernstian-shift towards the potentials of the used biocatalysts in those pseudo-capacitive elements