3D ordered nanoporous NiMoO4 for high-performance supercapacitor electrode materials

Abstract

3D ordered nanocrystalline nanoporous NiMoO₄ has been synthesized by nanocasting from mesoporous silica KIT-6, and characterized by low and wide-angle powder X-ray diffraction (PXRD), high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), BET, and BJH techniques, confirming the formation of a 3D high-ordered nanoporous structure of nanocrystalline (∼9 nm) NiMoO₄ with high specific surface area (141 m² g⁻¹) and bimodal pore size distribution (4.5 and 12.5 nm). The electrochemical properties of the nanoporous NiMoO₄ have been evaluated as electrode material for supercapacitors in a three-electrode configuration in aqueous 3 M KOH solution. The material exhibits superior electrochemical performance including high area specific capacitance (ASC) of 4.25 F cm⁻² (2835 F g⁻¹) at 3 mA cm⁻², excellent rate capability (2.18 F cm⁻² at 120 mA cm⁻²), excellent cycling stability in 6000 continuous cycles at different current densities (only 8.4% loss after 3000 cycles at 7.5 mA cm⁻²), and high energy and power densities (141.75 W h kg⁻¹ in 0.6 kW kg⁻¹, and 72.6 W h kg⁻¹ in 24 kW kg⁻¹). The superior electrochemical performance of the nanoporous NiMoO₄ electrode has been attributed to its structural features, including a 3D high-ordered nanoporous structure with conjunct bimodal pores which facilitates mass transfer and electrolyte accessibility, a high specific surface area which provides more active sites for the pseudocapacitive reactions, and nanosized walls which shorten diffusion paths. These results make the 3D nanoporous NiMoO₄ a promising electrode material for high-performance supercapacitors.