High-performance ZnCo₂O₄@CeO₂ Core@shell microspheres for catalytic CO oxidation

In this paper, we report a self-assembly method to synthesize high-quality ZnCo₂O₄@CeO₂ core@shell microspheres with tunable CeO₂ thickness. ZnCo₂O₄ spheres were first synthesized as the core, followed by a controlled CeO₂ shell coating process. The thickness of CeO₂ shell could be easily tuned by varying the feeding molar ratio of Ce/Co. Transmission electron microscope (TEM) images and scanning transmission electron microscope (STEM) image have identified the core@shell structure of these samples. In CO oxidation tests these ZnCo₂O₄@CeO₂ core@shell microspheres exhibited promising catalytic performance, and the catalytic activity of the best sample is even close to the traditional noble metal-CeO₂ system, attaining 100% CO conversion at a relatively low temperature of 200 °C. Cycling tests confirm their good stability of these core@shell microspheres besides activity. Their high catalytic performance should be attributed to the core@shell structure formation, and moreover further H₂-temperature-programmed reduction (TPR) results revealed the possible synergistic effects between the two components of ZnCo₂O₄ and CeO₂.