Enhanced impacts of reduction on Co3O4 model catalysts by NaBH4 in the hydrolysis of ammonia borane

The development of efficient and cost-effective nano catalysts for the room-temperature hydrolysis of ammonia borane (AB) is crucial for its practical utilization in hydrogen (H₂)-based fuel cells. This study specifically investigates the promotional effects on reduced Co₃O₄ catalysts induced by varying amounts of NaBH₄ during the hydrolytic dehydrogenation of ammonia borane. The morphology, structure, surface chemical states and magnetic property of Co₃O₄ before and after reduction were comprehensively analyzed to elucidate the factors influencing catalytic behavior during hydrolysis. Additionally, DFT calculations were employed to associate the high activity of Co₃O₄ with two key factors: oxygen vacancies and Co⁰ species generated after reduction, resulting in V_O-rich cobalt/oxide interfaces. Conversely, a slight decrease in catalytic activity was attributed to over-reduction leading to an excess of Co⁰ species dominating the catalysts. It can be inferred that the oxide phase not only acts as a precursor and support for the reduced nanosized cobalt active component but also serves as a critical catalyst component that enhances water activation.