Controlled growth of spinel NiCo2O4 nanostructures on carbon cloth as a superior electrode for supercapacitors

Abstract

In this study, the morphology conversion of bimetallic NiCo₂O₄ nanostructures on carbon fiber cloth (CFC) was achieved via a simple hydrothermal approach with different precursor salts. As expected, the surface morphology has been successfully driven by varying the precursor. Typical NiCo₂O₄ nanowall-networks and porous nanoflake microstructures have been grown when using the nitrate and chloride precursors respectively. As an advantage of their unique structural features, they have shown different electrochemical activity towards supercapacitor applications. The as-grown NiCo₂O₄ nanowall-network structure delivers a maximum capacitance of 1225 F g⁻¹ at a high current density of 5 A g⁻¹ and excellent durability. However, a limited specific capacitance of only 844 F g⁻¹ at a current density of 1 A g⁻¹ was achieved for NiCo₂O₄ nanoflakes. This variation in the electrochemical features such as specific capacitance, rate capability and cyclic stability is mainly due to their structural discrepancies which have been driven by the precursors during the growth process. From this investigation it can be concluded that precursors with different anions also greatly influence the growth kinetics of metal oxide nanostructures. In this case, we suggest that the directly grown NiCo₂O₄@CFC with the desired microstructure will be a potential electrode for next generation flexible supercapacitors.