Initially the aqueous dispersion of GO was ultrasonicated with H3PO4 and the subsequent thermal annealing at 800 °C for 0.5 h and the elemental analysis from XPS revealed that the atomic percentage of phosphorus and the oxygen are found to be 1.30 and 10.39 %, respectively. The prepared P-doped graphene was assembled as a symmetric supercapacitor In another literature, Fan et al. prepared the P-doped graphene using three different precursors such as phytic acid, potassium dihydrogen phosphate and phosphoric acid by single step hydrothermal method at 170 °C for 12 h . The content of phosphorus in the XPS analysis of P-doped graphene synthesized using three different precursors such as phytic acid, potassium dihydrogen phosphate and orthophosphoric acid is estimated to be about 0.9, 1.33 and 2.28 at. %, respectively. The CV profile of three P-doped graphene materials along with RGO is displayed in Fig. and the existence of redox peaks are attributed to the faradaic behaviour by the electrochemically active Phosphorus atoms. From the Fig. , the P-doped graphene derived from phytic acid has achieved the specific capacitance of 388.5 F g -1 at 1 mA cm -2 in1 M H2SO4 electrolyte solution and attained the 99% retention in capacitance from its initial value after 10000 cycles. The substantial improvement in the capacitive performance is attributed to the fact that the polarisation happened in the graphene framework because of the difference in electronegativity of phosphorus and carbon and then the pseudocapacitance is enriched by the doped phosphorus atoms at edge or defective sites. respectively. Due to high temperature during laser irradiation, some phosphorus atoms form phosphate, that can assist the dehydration of substrate to form an amorphous carbon char. Thus, it leads to the reduction in the content of phosphorus. The calculated specific capacitance of LIPG is 206 F g -1 at 0.025 A g -1 in 3 M KOH solution and two-fold higher than graphene without P-doping. Both formation of hierarchical porous structure and P-doping are thought to be essential factors for the improved performance. Recently, Suresh Balaji et al. prepared the P-doped graphene by supercritical fluid processing using water and sodium phosphate as the solvent and precursor involving the three various weight compositions of GO and precursor, respectively . From the various combinations, the P-doped graphene which was derived from the dopant and the GO are in the weight ratio 1:1 has achieved the maximum specific capacitance of 518 F g -1 at 1 A g -1 in 1 M H2SO4 as shown in Fig. and excellent stability with capacitance retention of 98% over 5000 cycles at 10 A g -1 . Importantly, the energy density of symmetric supercapacitor cell increased from 8 to 29 Wh Kg -1 by 3.4 times if the electrolyte is changed from H2SO4 to KI/H2SO4 due to the increased pseudocapacitance behaviour by the incorporation of KI as a redox additive and too displayed in Fig. . The plausible electrochemical mechanism with KI as a redox additive is represented as shown below: respectively. The appreciable variation in capacitance is caused by various factors such as good wettability, hydrophilicity and rapid exfoliation as well as circular functionalization method.