Synergetic effect of nitrogen and sulfur co-doping in mesoporous graphene for enhanced energy storage properties in supercapacitors and lithium-ion batteries

Nitrogen and sulfur co-doped mesoporous graphene (NSMG) was fabricated via a hydrothermal method followed by heat treatment utilizing graphite oxide (GO), tri-block co-polymer P123 and thiourea as the N and S source. The porous structure of the NSMG was controlled by heat treatment at 600 degrees C and 800 degrees C thus obtaining NSMG600 and NSMG800 which had specific surface areas of 966 and 1335 m(2)g(-1), respectively. X-ray photoelectron spectroscopy (XPS) of the NSMGs demonstrated the presence of active pyridinic-N, pyrrolic-N, graphiticN, pyridinic N- oxide, thiophene and -SOx groups in the structure. The N and S contents and configurations were controlled by annealing temperature hence influencing the performance in supercapacitors (SC) and lithium-ion batteries (LIBs). There was improved electrolyte ion mobility and lithium-ion diffusion for both SCs and LIBs respectively. The improved performance could be attributed to the unique structural features such as plentiful defects, wrinkles, abundant pores, and N/S co-doping. NSMG600 exhibited the highest capacitance of 261 F g(-1) at 0.5 A g(-1) in SCs while NSMG800 showed the best performance in LIBs with a discharge capacity of 460 mAh g(-1) at 100 mA g(-1) with good cycling stability (440 mAh g(-1)) and superior rate capability. Thus NSMGs exhibit potential application in high-performance energy storage devices.