Nitrogen/oxygen co-doped monolithic carbon electrodes derived from melamine foam for high-performance supercapacitors

Abstract

A novel monolithic carbon sponge is prepared by a ZnCl₂-assisted carbonization of commercial melamine foam (MF) at 800 °C in a N₂ atmosphere. The as-prepared nitrogen/oxygen co-doped carbon sponges (NOCSs) can be directly applied as monolithic electrodes for supercapacitors without using any additives. It is found that ZnCl₂ activation plays an important role in improving the supercapacitive behavior of NOCSs. Compared with the NOCS without ZnCl₂ activation treatment, the optimal NOCS-1/10, obtained with a ZnCl₂/MF weight ratio of 1 : 10, has the best capacitive performance due to its unique porous architecture, rich pseudocapacitance-active species, and good electron/ion transfer feature. It exhibits a high specific capacitance (242 F g⁻¹ at a current density of 0.5 A g⁻¹ and 325 F g⁻¹ at a scan rate of 10 mV s⁻¹) and good electrochemical cyclability (97% after 10 000 cycles at 5.0 A g⁻¹). When being further assembled into an all-solid-state supercapacitor (PVA/KOH electrolyte), it can deliver an energy density of 4.33 W h kg⁻¹ at a power density of 250 W kg⁻¹ and 3.13 W h kg⁻¹ at a power density of 3 kW kg⁻¹.