A. Bhardwaj, U. Okoroanyanwu, J.J. Watkins
University of Massachusetts Amherst,
Keywords: graphene, photothermal processing, supercapacitors
Summary:Graphene offers superior electrical conductivity and surface area, which holds great promise for energy storage applications including supercapacitors. Current preparation methods for graphene and graphene-like materials require relatively long processing times, extremely high temperatures within controlled atmospheres, and/or involve multi-step reactions that present challenges for high throughput fabrication of graphene-based devices. Moreover, supercapacitor devices fabricated using graphene exhibit low areal capacitance thereby limiting their applications. We report a photothermal route to large-scale production of graphene within milliseconds from electrochemically grown polyaniline using high intensity xenon flash lamp on carbon fiber at ambient conditions. The xenon flash lamp provides large-area illumination and a wide emission band (300 nm –1100 nm) that was used to convert the polymeric material directly into graphene upon millisecond exposures. Rapid photothermal heating of polyaniline leads to the formation of macro porous graphene with a fibrous morphology, excellent conductivity, and good adhesion to the carbon fiber all of which facilitate the transport of ions through the material and improve performance of the device. The fabricated supercapacitors exhibited a very high areal capacitance of 15 mF/cm2 at 50 mV/s with retention of more than 80% of its capacitance even after increasing the scan rate to 500 mV/s. The preparation of high-quality graphene via photothermal pyrolysis of polyaniline is amenable to high throughput processing, and thus large-scale production of electrochemical energy storage devices can be enabled by this approach.