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[sbnd]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[sbnd]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[sbnd]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[sbnd]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[sbnd]CoMoO₄ NSAs electrode delivers a remarkable specific capacity of (~236.86 mA h g⁻¹ at 2 A g⁻¹), excellent rate capability (~92.44% retains even at 10 A g⁻¹), and superior cycling stability (~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[sbnd]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[sbnd]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[sbnd]CoMoO₄ NSAs are promising candidates for electrodes in high-performance supercapacitors.