Using nitroaromatic fused-heterocycle molecules as nitrogen source to hugely boost the capacitance performance of graphene

Nitroaromatic pollutants with unusually strong adsorption affinity are highly attractive candidates for creating 2D molecular assemblies on the surface of graphene, which is crucial to prepare high-quality N-doped graphene by post-treatment. Herein, the few-layered crumpled N-doped graphene (5-NIGN) with high N content is successfully prepared by mixing 5-nitroindole (5-NI), ammonia, and graphene oxide (GO) and using a simple hydrothermal method followed by the post-treatment process of vacuum freeze-drying and annealing. It is found that the rapid assembly of 5-NI effectively suppresses the aggregation of the products in the reduction process of GO, so that the thickness of as-prepared 5-NIGN is 4.21 nm, very close to that of GO (4.01 nm). Compared with the N-doped graphene (GN) derived from the system of GO containing ammonia (341 F g(-1)), 5-NIGN exhibits higher capacitance of 457.4 F g(-1) at 1 A g(-1) and prominent long-term life (115% of capacitance maintenance upon 10,000 cycles) within the voltage window of 1.0 V. Furthermore, the supercapacitor assembled by 5-NIGN electrodes can deliver the energy density of 15.5 Wh kg(-1) 18.5 Wh kg(-1) at the power density of 8000 W kg(-1) 800 W kg(-1). These results indicate that the 5-NIGN material will have potential advantages in the realm of electrochemical energy storage. (C) 2020 Elsevier Ltd. All rights reserved.