Hollow CeO2 spheres conformally coated with graphitic carbon for highperformance 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 m(2).g(-1)), a well-defined hollow structure (a monodisperse size of similar to 260 nm with inner diameter of similar to 200 nm and shell thickness of similar to 30 nm), and nanocrystals of CeO2 (similar to 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.