Hollow CeO2 spheres conformally coated with graphitic carbon for high-performance supercapacitor electrodes

Electrode material is essential for supercapacitors which are an important energy storage device that can deliver high power. Herein, we report the successful synthesis of hollow CeO₂ nanospheres conformally coated with graphitic carbon (H-CeO₂@GC) via a facile hydrothermal method as a kind of electrode materials of supercapacitors. The as-prepared H-CeO₂@GC hollow spheres presented a high specific surface area (153 m²∙g⁻¹), a well-defined hollow structure (a monodisperse size of ∼260 nm with inner diameter of ∼200 nm and shell thickness of ∼30 nm), and nanocrystals of CeO₂ (∼10 nm) conformally encapsulated in ultra-thin graphitic carbon layers. When applied in supercapacitors, the H-CeO₂@GC hollow spheres delivered a high specific capacitance of 501 F∙g⁻¹ at a current density of 1 A∙g⁻¹, a high energy/power density, excellent rate capability and long cycle life owing to its unique architecture. In particular, an energy density of 17.2 Wh∙kg⁻¹ with a power density of 2600 W∙kg⁻¹ was achieved. The supercapacitors retained 85% of the specific capacitance (refer to 1 A∙g⁻¹) even at a high current density of 15 A∙g⁻¹ and exhibited excellent cycling stability with 93% of the capacity retention after 5000 cycles at 10 A∙g⁻¹. This work offers a new approach to developing high-performance supercapacitors using the strategy of combining hollow nanosphere architecture and conductive graphitic carbon nanocoating.