Waste sugar solution polymer-derived N-doped carbon spheres with an ultrahigh specific surface area for superior performance supercapacitors.

Waste sugar solution (WSS), a waste by-product of manufacturing vitamin C, contains abundant waste acids and organics. In this work, a N/O -enriched copolymer was synthesized via a facile polymerization via the hydrogen bonding of O -containing functional groups and melamine and the crosslinking of aldehyde groups. Subsequently, N -doped carbon spheres were prepared by a typical carbonation/activation method. Remarkably, benefiting from an ultrahigh specific surface area (3612 m2/g) and rich heteroatom content (4.3% for N, 8.8% for O), the carbon spheres deliver a high specific capacitance of 387 F/g at 50 mA/g and 283 F/g at 5 A/g with 6 M KOH in two-electrode system. The assembled symmetric electric double-layer capacitor exhibits high energy density of 10.83 Wh/kg at 11.10 W/kg. This research provides a facile method for preparing N / O -doped carbon spheres by WSS, and confirms the excellent electrochemical performance of WSS-derived carbons in energy storage applications. [Display omitted] • N-doped carbon spheres are prepared by waster sugar solution. • Two nitrogen doping strategies are compared and discussed in detail. • The as-prepared samples display good electrochemical performance. [ABSTRACT FROM AUTHOR]