In this study, the impact of urea and 2-hydroxyethyl cellulose as precipitating and stabilizing agents on the morphology and catalytic efficiency of nickel oxide (NiO) nanoparticles was explored under hydrothermal conditions at 130 °C for 13 hours. The structural and morphological properties of the synthesized NiO were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM), revealing distinct differences in particle size and shape. TEM analysis showed that NiO synthesized with urea (NU-C) exhibited a more uniform shape compared to that synthesized with 2-hydroxyethyl cellulose (NH-C). Catalytic activity was evaluated through the decomposition of hydrogen peroxide (H₂O₂) in the presence of dispersed NiO powders. Kinetic studies demonstrated that the reaction rate constant for NU-C was approximately 1.5 times higher than that for NH-C, highlighting the superior catalytic efficiency of the urea-based NiO. The activation energies and thermodynamic parameters (ΔH, ΔS, and ΔG) were determined via Arrhenius plots, indicating that the differences in activation energy correlated with the morphological variations. These findings suggest that the shape and size of NiO nanoparticles play a critical role in enhancing their catalytic performance in H₂O₂ decomposition.