Wang et al. investigated the electrochemical capacitance of N, P co-doped graphene by thermal exfoliation of GO at 800 °C for 30 s accompanied by thermal annealing at 800 °C for 2 h under N2 atmosphere using ammonium phosphate as the precursor . The elemental composition of N, P co-doped graphene revealed that it has the content of 13.4, 2.9 and 4.3 at. % belonging to oxygen, nitrogen and phosphorus, respectively. The electrical conductivity of N, P co-doped graphene (575 S m -1 ) is greater than P-doped graphene (290 S m -1 ) which might be attributed to the fact that the content of phosphorus in former is higher than latter. Similarly, the electrical conductivity of N, P co-doped graphene (575 S m -1 ) is lesser than N-doped graphene (820 S m -1 ) which might be attributed to the fact that the content of nitrogen in former is lesser compared to latter. Thus, it has been suggesting that the content of doped heteroatom has significant impact on the electrical conductivity. From Fig. , it is apparent that the N, P codoped graphene acquired the specific capacitance of 165 F g -1 at 100 mA g -1 in 6 M KOH solution which is higher than nitrogen and phosphorus doped graphene and the improved capacitive performance is correlated to the fact that the pseudocapacitive behaviour is increased owing to the presence of oxygen containing phosphorus substituents and the Ncontaining moities such as pyridinic and pyrrolic structures. In another report, the N, P codoped graphene was produced by the thermal activation of GO with dicyandiamide and H3PO4 first at 500 °C for 4 h accompanied by thermal annealing at 900 °C for 1 h under Ar atmosphere . The optimised N, P co-doped graphene has attained the enhanced specific capacitance of 244.6 F g -1 in 6 M KOH solution at 0.1 A g -1 . It was found that both pore volume and SSA increased with rise in loading of the phosphoric acid. Moreover, the atomic content of both phosphorus and oxygen increased with the quantity of precursor while the atomic content of nitrogen reduces. Thus, the capacitive performance is enhanced by the orthophosphoric acid activation by introducing the more pore volume that facilitate the rapid diffusion of ions and also by the presence of phosphate functionalities which increases the pseudocapacitance. Wen et al. synthesized the N, P co-doped graphene monolith by hydrothermal, freeze drying and thermal annealing in the sequential order using melamine phosphate as the source and delivered the specific capacitance of 183 F g -1 at 0.05 A g -1 in 1 M H2SO4 electrolyte . The estimated doping contents of nitrogen and phosphorus are found to be 4.3-6 and 1-3 at. %, respectively.