Ultrafast response planar on-chip micro-supercapacitors based on nitrogen and oxygen co-doped graphene quantum dots with both ultrahigh power and energy densities

Great results had been achieved in the research of graphene-based planar on-chip micro-supercapacitors. The performances of fabricated micro-supercapacitors had been greatly improved. However, the energy characteristics of graphene-based planar on-chip micro-supercapacitors are generally low due to few active sites of graphene. Nitrogen and oxygen co-doped graphene quantum dots have the nanometer size, more active sites, and rich edge defects, are conducive to ion adsorption and desorption, and can solve the above-mentioned disadvantages of graphene. In this article, all-solid-state planar on-chip micro-supercapacitors based on nitrogen and oxygen co-doped graphene quantum dots with both ultrahigh power and energy densities were fabricated by modified liquid-air interface self-assembly and photolithography for the first time. Planar on-chip electrodes were provided with a nanoscale thickness of 6 nm and an interdigital electrode width of 3 mu m. Energy density of 11.49 mWh cm(-3), power density of 41.42 W cm(-3), and time constant of 3.16 mu s were demonstrated. It should be emphasized that the above-mentioned energy density and power density are the highest for the planar on-chip micro-supercapacitors based on nitrogen and oxygen co-doped graphene quantum dots reported to date. The capacitance retention was 99% after 10000 cycles at 5000 V s(-1).