Flexible self-charging supercapacitor based on graphene-Ag-3D graphene foam electrodes

A flexible three-dimensional porous graphene foam-based supercapacitor (GFSC) is presented here for energy storage applications. With a novel layered structure of highly conductive electrodes (graphene-Ag conductive epoxy-graphene foam), forming an electrochemical double layer, the GFSC exhibits excellent electrochemical and supercapacitive performance. At a current density of 0.67 mA cm(-2), the GFSCs show excellent performance with areal capacitance (38 mF cm(-2)) about three times higher than the values reported for flexible carbon-based SCs. The observed energy and power densities (3.4 mu W h cm(-2) and 0.27 mW cm(-2) respectively) are better than the values reported for carbon-based SCs. Analyzed under static and dynamic bending conditions, the GFSCs are stable with up to 68% capacitance retention after 25000 charge-discharge cycles. The light-weight, cost-effective fabrication and no self-heating make the GFSCs a promising alternative to conventional source of energy in the broad power density ranging from few nW cm(-2) to mW cm(-2). In this regard, GFSC was integrated with a flexible photovoltaic cell resulting in a flexible self-charging power pack. This pack was successfully utilized to power continuously a wearable CuO nanorod based chemi-resistive pH sensor.