Low-crystalline nickel hydroxide nanosheets embedded with NiMoO4 nanoparticles on nickel foam for high-performance supercapacitor applications

Abstract

Transition metal hybrid nanomaterials have attracted wide attention in the field of energy storage due to their rich redox activity and good conductivity and structural stability. In this work, low-crystalline Ni(OH)₂·0.75H₂O nanosheets embedded with NiMoO₄ nanoparticles (NiMo-LDH) on nickel foam (NF) were synthesized by a simple urea-assisted hydrothermal method. By optimizing the Ni/Mo molar ratio and urea concentration in the initial reaction solution, the composition of NiMo-LDH was effectively controlled, which was found to have a crucial impact on the electrochemical performance of the NiMo-LDH electrode. The NiMo-LDH (Ni2Mo1–urea0.2 M) electrode shows porous ultra-thin two-dimensional characteristics and NiMoO₄ nanoparticles (3–5 nm) embedded in nickel hydroxide nanosheets can provide more exposed active sites, accelerate electron transport and enhance the faradaic reaction. The Ni2Mo1–urea0.2 M electrode exhibits an extremely high capacitance of 4.4 F cm⁻² (2001 F g⁻¹) at 4 mA cm⁻² (1.8 A g⁻¹), with 63% capacitance retention observed at 48 mA cm⁻² (21.8 A g⁻¹). More importantly, the asymmetric supercapacitor (ASC) assembled using Ni2Mo1–urea0.2 M as the positive electrode presents an energy density value of 70.76 W h kg⁻¹ at 318.84 W kg⁻¹ and 26.24 W h kg⁻¹ even at 7680 W kg⁻¹ along with good stability of 82% over 5000 cycles at 100 mV s⁻¹.