Synthesis of Phosphorus-Doped Graphene and its Wide Potential Window in Aqueous Supercapacitors

Phosphorus-doped (P-doped) graphene with the P doping level of 1.30 at% was synthesized by annealing the mixture of graphene and phosphoric acid. The presence of P was confirmed by elemental mapping and X-ray photoelectron spectroscopy, while the morphology of P-doped graphene was revealed by using scanning electron microscopy and transmission electron microscopy. To investigate the effect of P doping, the electrochemical properties of P-doped graphene were tested as a supercapacitor electrode in an aqueous electrolyte of 1 M H2SO4. The results showed that doping of P in graphene exhibited significant improvement in terms of specific capacitance and cycling stability, compared with undoped graphene electrode. More interestingly, the P-doped graphene electrode can survive at a wide voltage window of 1.7 V with only 3 % performance degradation after 5000 cycles at a current density of 5 Ag-1, providing a high energy density of 11.64 Whkg(-1) and a high power density of 831 Wkg(-1).