Nickel oxide nanoparticles catalyst for enhancing green hydrogen production: effect of preparation conditions

This work focused on the synthesis of nickel oxide under varying hydrothermal conditions as a non-precious and efficient catalyst for NaBH₄ hydrolysis to generate hydrogen. The structural, morphological, and textural features of the calcined samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and N₂-physisorption techniques. XPS analysis confirmed the presence of Ni²⁺ and Ni³⁺ species, with varying Ni³⁺/Ni²⁺ ratios across the samples. The NH-200 samples showed the highest hydrogen generation rate, approximately 1290 at 323 K, attributed to the enhanced redox behavior of Ni³⁺ ions. N₂-adsorption results revealed mesoporous structures with distinct surface areas and pore characteristics. The catalytic performance was evaluated at 35-50 °C, showing enhanced activity with increasing temperature and NaBH₄ concentration (up to 4.5 wt.%). Activation energies were found to be below 59 kJ mol^-1. The catalyst maintained good stability over five consecutive cycles with only a slight performance decline. These findings confirm that NiO is a cost-effective, active, and reusable catalyst for hydrogen generation via NaBH₄ hydrolysis.