Synthesis Route as a Key Determinant of Structural, Textural, and Electrochemical Behavior in NiAl2O4 Spinel Nanoparticles

Abstract NiAl2O4 spinel oxides were synthesized using co-precipitation, hydrothermal, and sol-gel routes using the same precursors and calcination conditions to evaluate the effect of synthesis route on their structural, textural, and electrochemical properties. The obtained materials were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and N2 adsorption-desorption analysis. Electrochemical performance was assessed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). XRD results confirmed the formation of cubic NiAl2O4 nanoparticles with average crystallite size of approximately 7, 6, and 5 nm for sol-gel, co-precipitation and hydrothermal methods, respectively. All samples exhibit mesoporous structures, with BET surface area measured of 72, 120, and 78 m2/g. the co-precipitated sample showed the highest surface area, while the sol-gel route led to improved crystallinity and phase purity. Despite moderate surface area, the hydrothermally synthesized NiAl2O4 demonstrated enhanced electrochemical performance, with a specific capacitance of ~300 F/g at 10 mV/s, along with reduced charge-transfer resistance and improved electronic/ionic conductivity. These results highlight the decisive role of synthesis strategy in tailoring the physicochemical properties of NiAl2O4 spinels.