Soft-template assisted morphology tuning of NiMoO4 for hybrid supercapacitors.

• NiMoO 4 with different morphology has been synthesized through hydrothermal method. • NiMoO 4 with flower-like morphology possesses a high SC of 947 F g −1 at 1 Ag−1. • Both Ni2+/Ni3+ and Mo6+/Mo4+ are involved in the charge storage mechanism. • A hybrid supercapacitor rGO||NiMoO 4 can exhibit an energy density of 37.7 Wh kg−1. • The supercapacitor possesses 94 % capacitance retention after 6000 cycles. The electrochemical performance of electrode materials depends on various physicochemical properties like particle size, morphology, porosity, etc. of materials. Herewith, a facile surfactant assisted hydrothermal route using cetyltrimethylammonium bromide (CTAB) and hexamethylenetetramine (HMT) is used to successfully synthesize nanostructured nickel molybdate (NiMoO 4) with various morphologies. It is found that NiMoO 4 possesses different morphologies when synthesized by using these surfactants. With change in morphology, there is a significant increase in diffusion coefficient for sample synthesized with CTAB. It is interesting to note that NiMoO 4 synthesized by using CTAB exhibit a high specific capacitance of 947 F g −1 when cycled at 1 A g −1 in 1 M KOH solution as compared to that of 322 F g −1 (synthesized without CTAB), which can be ascribed to its flower-like shape with uniform porosity. Both Ni2+/Ni3+ and Mo6+/Mo4+ redox couples are involved in the capacitive characteristic of NiMoO 4 , as found from the XPS study. Additionally, a hybrid supercapacitor has been assembled using NiMoO 4 as positive electrode and reduced grapgene oxide (rGO) as negative electrode, which can exhibit 107 F g −1 with an operating voltage of 1.6 V with excellent cycling stability of maintaining 94 % capacitance retention after 6000 cycles in 1 M KOH solution. The hybrid supercapacitor can possess an energy density of 37.7 Wh kg−1 and a power density of 8 kW kg−1. Thus, this study enables the importance of tuning the morphology to enhance the capacitance property of transition metal oxide based electrode materials for supercapacitor applications. [Display omitted] [ABSTRACT FROM AUTHOR]