Using hydroxylamine as a reducer to prepare N-doped graphene hydrogels used in high-performance energy storage

•N-doped graphene hydrogels (NGHs) were prepared by thermally treating graphene oxide.•The optimum conditions were determined by using hydroxylamine as reducing agent.•The capacitor assembled by the optimum NHGs exhibit good capacitive performance.

Solvothermal method is used to obtain N-doped graphene hydrogels (NGHs) using hydroxylamine hydrochloride or hydroxylamine (HA) as the chemical reductant and dopant. During the process, N-doping and reduction of graphene oxide have been achieved simultaneously. The products have been characterized by X-ray diffraction, X-ray photoelectron, Raman spectroscopy and electrochemistry. The results show that the electrical conductivity, microstructure and doping level of NGHs are influenced by the type and quantity of reductants, temperature and time of the reaction. Their capacitive behavior has been investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy in an alkaline electrolyte using the two-electrode symmetric capacitor test. The NGHs prepared at 150 °C for 12 h using HA as reductant (NGH–HA12) has N-doping level of 4.32% in atom and exhibits a specific capacitance of 205 F g−1 and good cycling stability. The energy density and power density can reach to 3.65 W h kg−1 and 20.5 kW kg−1 at a discharge of 100 A g−1 for the symmetric capacitor assembled using NGH–HA12.