Efficient hydrogen generation via NaBH4 hydrolysis over Co3O4 catalysts: The role of calcination temperature, valence, and reaction kinetics

Abstract

A novel cobalt oxide (Co₃O₄) catalyst for hydrogen production via the hydrolysis of sodium borohydride (NaBH₄) was synthesized using a combined hydrothermal synthesis and calcination method. The catalysts were characterized by XRD, TEM, and XPS to elucidate their structural and compositional properties. The Co₃O₄ catalyst must undergo a surface reduction induction period to trigger its high catalytic activity, yet its bulk phase maintains its original crystalline structure. The results demonstrate that the Co₃O₄ catalyst calcined at 800 °C exhibits the highest hydrogen production rate of up to 4145.8 mL min⁻¹·g⁻¹, which is much higher than that of the CoO catalyst. This can be ascribed to its optimized crystallinity, mixed valence of Co²⁺/Co³⁺, and more oxygen vacancies. Meanwhile, the catalyst calcined at 800 °C also displays excellent cycling stability. The study further investigated the effects of NaBH₄ and NaOH concentrations on catalytic activity, revealing that the NaOH concentration can significantly affect the reaction rate. Kinetic analysis indicated that the hydrolysis of NaBH₄ over the Co₃O₄ catalyst follows a zero- order reaction with an activation energy of 37.9 kJ mol⁻¹. This research underscores the potential of Co₃O₄ as an efficient and cost-effective catalyst for sustainable hydrogen production from NaBH₄ hydrolysis.