Two-dimensional Graphene Paper Supported Flexible Enzymatic Fuel Cell

Application of enzymatic biofuel cells (EBFCs) in wearable or implantable biomedical devices requires flexible and biocompatible electrode materials. To this end, freestanding and low-cost graphene paper is emerging among the most promising support materials. In this work, we have exploited the potential of using graphene paper with two-dimensional active surface (2D-GP) as carriers for enzyme immobilization to fabricate EBFCs, which represents the first case of flexible graphene papers directly used in EBFCs.

The 2D-GP electrodes were prepared via the assembly of graphene oxide (GO) nanosheets into paper-like architecture, followed by reduction to form layered and cross-linked networks with good mechanical strength, high conductivity and little dependent on the degree of mechanical bending. 2D-GP electrodes served as both a current collector and an enzyme loading substrate that can be used directly as bioanode and biocathode.

Pyrroloquinoline quinone dependent glucose dehydrogenase (PQQ-GDH) and bilirubin oxidase (BOx) adsorbed on the 2DGP electrodes both retain their biocatalytic activities. Electron transfer (ET) at the bioanode required Meldola blue (MB) as an ET mediator to shuttle electrons between PQQ-GDH and electrode, but direct electron transfer (DET) at the biocathode was achieved.

The resulting glucose/oxygen EBFC displayed a notable mechanical flexibility, with wide open circuit voltage up to 0.665 V and maximum power density of approximately 4 µW/cm2 both fully competitive with reported values for related EBFCs, and with the mechanical flexibility and facile enzyme immobilization as novel merits.