Facile synthesis of hierarchical flower-like NiMoO4-CoMoO4 nanosheet arrays on nickel foam as an efficient electrode for high rate hybrid supercapacitors

Binder-free hierarchical flower-like NiMoO4-CoMoO4 nanosheet arrays (NSAs) have been successfully grown on nickel (Ni) foam surface via a facile one-step chemical bath deposition method followed by calcination treatment. The as-prepared NiMoO4-CoMoO4 NSAs electrode material has been effectively used as a battery-type material for supercapacitor applications. Surface morphological and structural studies reveal that the as-fabricated NiMoO4-CoMoO4 electrode exhibits a flower-like heterostructures constructed with interconnected nanosheet arrays. In a three-electrode system, the potential plateaus from the cyclic voltammetry and galvanostatic charge-discharge measurements indicate that the obtained NiMoO4-CoMoO4 NSAs electrode exhibits Faradic battery-type redox behaviour, which is different form the profiles of carbon-based materials. As a battery-type material, NiMoO4-CoMoO4 NSAs electrode delivers a remarkable specific capacity of (similar to 236.86 mA h g(-1) at 2 A g(-1)), excellent rate capability (similar to 92.44% retains even at 10 A g(-1)), and superior cycling stability (similar to 97.19% at 6 A g(-1) over 5000 cycles), which are much higher than those of the bare NiMoO4 and CoMoO4 electrodes. The superior electrochemical properties of the NiMoO4-CoMoO4 composite material are due to the synergetic effect from CoMoO4 and NiMoO4 and to the fact that the hierarchical nanosheet arrays provide abundant electroactive sites for rapid redox reactions. Additionally, hybrid supercapacitor (HSC) has been assembled using NiMoO4-CoMoO4 NSAs/Ni foam as the positive electrode and graphene-ink/Ni foam as the negative electrode. It is found to exhibit a good cycling stability and a high specific energy of 27.58 Wh kg(-1) at a specific power of 636.05 W kg(-1). Thereby, these electrochemical performances suggest that the as-fabricated NiMoO4-CoMoO4 NSAs are promising candidates for electrodes in high-performance supercapacitors.