Porous nitrogen-rich carbon materials from carbon self-repairing g-C3N4 assembled with graphene for high-performance supercapacitor

Abstract

Nitrogen-rich carbon material derived from carbon self-repairing g-C₃N₄ is self-assembled with graphene oxide (GO) to form a porous structure. Different from the pristine g-C₃N₄, which has scarcely been employed in supercapacitors because of its low charge mobility, the carbon self-repairing g-C₃N₄ (C-C₃N₄) shows an improved electrochemical activity. After carbon-repairing, a delocalized big π-bond can be formed by the homogeneous C-substitution for N atoms or the formation of new interstitial C–N bond. The extending π-conjugation planar layer of C-C₃N₄ possesses a closer contact with GO to form a three-dimensional (3D) pore structure, which ensures good mobility for electrons and quick access for electrolytes. Under the optimum C-repairing content of 5.99 at%, the C-C₃N₄@rGO exhibited high specific capacity of 379.7 F g⁻¹ and energy density of 52.7 W h kg⁻¹ at a current density of 0.25 A g⁻¹. Moreover, the electrode kept 85% capacity retention after 10 000 cycles at a high constant current density of 10 A g⁻¹. The active sites of pseudocapacitance can be confirmed in the oxygen-containing groups and the carbon atoms close to the nitrogen by the XPS results.