A Simple and Scalable Route to Synthesize Co Cu Co O @Co Cu Co O Yolk-Shell Microspheres, A High-Performance Catalyst to Hydrolyze Ammonia Borane for Hydrogen Production.

Yolk-shell structured micro/nano-sized materials have broad and important applications in different areas due to their unique spatial configurations. In this study, yolk-shell structured Co O @Co O is prepared using a simple and scalable hydrothermal reaction, followed by a calcination process. Then, Co Cu Co O @Co Cu Co O microspheres are synthesized via adsorption and calcination processes using the as-prepared Co O @Co O as the precursor. A possible formation mechanism of the yolk-shell structures is proposed based on the characterization results, which is different from those of yolk-shell structures in previous study. For the first time, the catalytic activity of yolk-shell structured catalysts in ammonia borane (AB) hydrolysis is studied. It is discovered that the yolk-shell structured Co Cu Co O @Co Cu Co O microspheres exhibit high performance with a turnover frequency (TOF) of 81.8 mol min mol . This is one of the highest TOF values reported for a noble-metal-free catalyst in the literature. Additionally, the yolk-shell structured Co Cu Co O @Co Cu Co O microspheres are highly stable and reusable. These yolk-shell structured Co Cu Co O @Co Cu Co O microsphere is a promising catalyst candidate in AB hydrolysis considering the excellent catalytic behavior and low cost.