Aqueous Gel-Casting Synthesis and the Characterization of Cobalt Oxide as a Catalyst Precursor for Sodium Borohydride Hydrolysis

Aqueous gel-casting provides a cost-effective and scalable approach for synthesizing nano-spherical Co3O4 powders, enabling precise control over particle morphology. In this study, Co3O4 powders were prepared using this method and evaluated as a catalyst precursor for the hydrolysis of sodium borohydride (NaBH4). The effects of the monomer (acrylamide, AM)-to-metal molar ratio and initiator content (ammonium persulphate, APS) on particle size and catalytic performance were systematically explored. X-ray diffraction (XRD) analysis confirmed the formation of the Co3O4 phase at 400 °C, while transmission electron microscopy (TEM) images revealed particle sizes ranging from 16 to 85 nm, with higher AM and APS concentrations promoting finer particles. The optimized catalyst achieved a high hydrogen generation rate (HGR) of 28.13 L min−1·cat.−1, demonstrating excellent catalytic activity. Moreover, in situ-formed cobalt boride, derived from Co3O4 calcined at 600 °C for 2 h, exhibited an activation energy of 51.81 kJ mol−1, comparable to Ru-based catalysts. This study underscores the aqueous gel-casting technique as a promising strategy for synthesizing efficient and low-cost hydrogen generation catalysts, offering an alternative to noble metal-based materials.