Efficient pH-universal aqueous supercapacitors enabled by an azure C-decorated N-doped graphene aerogel

Abstract

Current aqueous supercapacitors (SCs) possess the relative low energy density, and there is therefore widespread interest in cost-effective fabrication of capacitive materials with promoted specific capacitance and/or broadened voltage window. Here, a redox-active azure C-decorated N-doped graphene aerogel (AC − NGA) is fabricated using a simple hydrothermal self-assembly method through strong noncovalent π-π interaction. AC − NGA highlights an excellent charge storage performance (a high 591F g−1 gravimetric capacitance under a current density of 1.0 A g-1 and ultrahigh voltage window of 2.3 V) under pH-universal conditions. The capacitive contribution of charge storage is 91.7%, exceeding or comparable to those of the best pseudocapacitors known. Furthermore, a symmetric AC − NGA//AC − NGA device realizes high energy and power densities (15.2–60.2 Wh kg−1 at 650–23,000 W kg−1) and excellent cycling stability in acidic, neutral, and basic aqueous solutions. This work offers a cost-effective strategy to combine redox dye molecules with heteroatom-doped graphene aerogel for building green efficient pH-universal aqueous supercapacitors.