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 µW 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.