A Simple and Scalable Route to Synthesize CoxCu1−xCo2O4@CoyCu1−yCo2O4 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 Co3O4@Co3O4 is prepared using a simple and scalable hydrothermal reaction, followed by a calcination process. Then, CoxCu1−xCo2O4@CoyCu1−yCo2O4 microspheres are synthesized via adsorption and calcination processes using the as‐prepared Co3O4@Co3O4 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 CoxCu1−xCo2O4@CoyCu1−yCo2O4 microspheres exhibit high performance with a turnover frequency (TOF) of 81.8 molhydrogen min−1 molcat−1. This is one of the highest TOF values reported for a noble‐metal‐free catalyst in the literature. Additionally, the yolk–shell structured CoxCu1−xCo2O4@CoyCu1−yCo2O4 microspheres are highly stable and reusable. These yolk–shell structured CoxCu1−xCo2O4@CoyCu1−yCo2O4 microsphere is a promising catalyst candidate in AB hydrolysis considering the excellent catalytic behavior and low cost. Yolk‐shell structured CoxCu1‐xCo3O4@CoyCu1–yCo3O4 is prepared by a simple and scalable route. A possible novel formation mechanism of the yolk‐shell structure is proposed based on the characterization results. The catalyst exhibit high performance with a turnover frequency (TOF) of 81.8 molhydrogen min‐1 molcat‐1, which is the highest value reported for a noble‐metal‐free catalyst.