Vertically/parallelly orientated growth of NiCo2O4 nanosheet onto surface of hierarchically N-doped porous carbon for improved supercapacitor

Here, hierarchically N-doped porous carbon (HPNC) with very high surface area was prepared by a facile one-pot pyrolysis of ethylenediaminetetraacetic acid tripotassium salt dihydrate used as the carbon/nitrogen source and pore activating agent. The NiCo2O4 nanosheets were vertically grown onto the surface of HPNC (V-NiCo2O4/HPNC) via a urea homogeneous precipitation method by a microwave heating. Whereas the parallelly orientated NiCo2O4/HPNC (P-NiCo2O4/HPNC) was fabricated by a usual water-bath heating. The loading content of V-NiCo2O4/HPNC was higher than that of the P-NiCo2O4/HPNC, thus resulting in the larger specific capacitance. V-NiCo2O4/HPNC exhibited the high specific capacity (434.8 F g-1 at 1.0 A g-1), good rate performance, cycle stability (capacitance retention of 103% at 5 A g-1 after 1000 cycles) and lower resistance, owing to the synergistic advantages of HPNC and vertically orientated NiCo2O4 nanosheets, which provided high electrical conductivity, and effective electrolyte ions and electrons transport path.