In another literature, Wang et al. developed the N, S co-doped graphene by hydrothermal method in a teflon lined autoclave at 160 °C for 4 h involving the different mass ratios of GO and L-cysteine (dopant) . The content of nitrogen and sulphur in the optimized N, S codoped graphene are 0.9 and 0.3 at. %, respectively. From Fig. , the extent of broadness in the redox peak of CV profile in N, S co-doped graphene is relatively higher than individually N and S doped graphene. The specific capacitance of optimized material has reached 566 F g - 1 at 0.5 A g -1 in 6 M KOH solution which is significantly greater than N and S-doped graphene delivering the values of 371 and 282 F g -1 , respectively and shown in It also delivered an excellent electrochemical stability showing the 98.6 % retention of the initial capacitance after 10,000 cycles. From XPS analysis, it is revealed that the content of nitrogen and sulphur are found to be 7.2 and 3.8 at. %, respectively. The marked rise in the capacitance is owing to the fact that the SBET of N, S co-doped graphene nanoribbons (312 m 2 g - High specific surface area of 1035 m 2 g -1 was obtained for the material that shown the maximum specific capacitance. The content of both nitrogen and sulphur in the optimised material from XPS was estimated to be about 1.96 and 0.97 at. %, respectively. This study evidently suggesting that the pH has significant impact on the properties and electrochemical performance towards supercapacitor applications. To further explore for practical usage, the prepared material was fabricated as a Tandem device that exhibit the capacitance which is same as that of single device and lighted red LED having the operating voltage of 1.8 V were displayed in both Fig. and, respectively.