Binder-free hybrid cobalt-based sulfide/oxide nanoarrays toward enhanced energy storage performance for hybrid supercapacitors

Cobalt-based materials have excellent electrochemical properties in theory and show great potential for improving the energy density of supercapacitors. The facile synthesis strategy and enhanced energy storage performance of self-supported cobalt-based sulfide/oxide nanoarrays (Co-S/Co-O) are demonstrated for hybrid supercapacitors in this work. In the Co-S/Co-O nanoarrays, the CoS sulfide and CoO oxide are intertwined with each other to form a whole, bringing positive synergistic effect for Faraday reaction and rapid electrons/ions transfer. As expected, Co-S/Co-O has higher specific capacity (1065 C g−1 at 1 A g−1) than CoS (176 C g−1) and CoO (702.5 C g−1). Furthermore, the Co-S/Co-O hybrid supercapacitor assembled with nitrogen-doped graphene as negative electrode shows higher specific capacitance (110 F g−1 at 1 A g−1) and specific energy (39.38 Wh kg−1 at a specific power of 800 W kg−1). The results show that Co-S/Co-O hybrid materials have great potential for energy storage applications. This work also provides a good strategy for improving the charge storage capacity of cobalt-based materials.