Synthesis of NiCo2O4/mesoporous carbon composites for supercapacitor electrodes

In this study, nickel cobaltite/mesoporous carbon composites are synthesized by reacting CoCl2, Ni (NO3)2 and nitric acid-treated biogas slurry mesoporous carbon using urea as hydrolyzing agent and hexadecyltrimethylammonium bromide (CTAB) as surfactant. The presence of Ni, Co, C and O peaks in the EDX results confirm that the composites are successfully synthesized. Interestingly at 350 °C, the composite surface morphology switched to cross-linked nanoflake structures interconnected with mesoporous carbon. The X-ray diffraction analysis of the NiCo2O4/mesoporous carbon composites reveals that the spinel structure of the NiCo2O4 is maintained in the composites. The nitrogen uptake increases with increasing annealing temperature to 300 °C then decreases at higher temperature (400 °C). The type IV isotherms are exhibited by all the composites. The contribution of mesopores increases with increasing annealing temperature: 32% for BC-NCo-200, 41% for BC-NCo-250, 56% for BC-NCo-300, 66% for BC-NCo-350 and 86% for BC-NCo-400. The NiCo2O4/mesoporous carbon composites exhibit high specific capacitance of 835 F g−1 at scan rate of 5 mV s−1 for sample annealed at 350 °C. The cyclic stabilities of the electrodes are above 90% after 50,000 cycles indicating that the synthesized composites are suitable candidates for supercapacitors.