Versatile template-free construction of hollow nanostructured CeO₂ induced by functionalized carbon materials

Hollow nanostructured metal oxides (HNMOs) have got great attention as advanced materials due to their fascinating physicochemical properties and significantly enhanced performance. However, because of the poor electron conductivity of most metal oxides, it is highly desirable to integrate metal oxides with conductive carbon materials for further achieving boosted behavior. Herein, induced by functionalized multi-walled carbon nanotubes (MWCNTs), a rationally designed hollow sphere CeO2/multi-walled carbon nanotube composite (HS-CeO₂/MWCNTs) has been successfully prepared for the first time via a facile template-free hydrothermal reaction followed by calcination. Particularly, the appropriate functional group density on the surface of MWCNTs can lead to the in situ growth of hollow sphere CeO₂. The HS-CeO₂/MWCNT composite featuring a unique 3D interpenetrating structure of hollow metal oxides and MWCNTs displays superior electrochemical performance to previously reported CeO₂-based composites, delivering excellent specific capacitance, brilliant cycling stability with 90.1% retention after 5000 cycles, and a prominent rate capability of 86.5% even at 10 A g⁻¹. It is worth noting that our newly developed synthesis method equally well applies for the preparation of hollow sphere CeO₂/activated carbon, hollow sphere CeO₂/graphene oxide, and hollow sphere Fe₂O₃/MWCNTs. The present work provides a versatile yet facile template-free approach to prepare hollow nanostructured metal oxide/carbon composites. Developing carbon material based hollow nanostructured metal oxides will open a new route to design advanced electrode materials for supercapacitors and other electrochemical energy storage devices.