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Graphical abstract Hollow CeO 2 nanospheres coated with graphitic carbon delivered a high specific capacitance, a high energy/power density, excellent rate capability and long cycle life owing to its unique architecture. Highlights • Hollow CeO 2 nanospheres conformally coated with graphitic carbon (H-CeO 2 @GC). • H-CeO 2 @GC delivered 501F∙g−1 at 1 A∙g−1 and retained 85% capacitance at 15 A∙g−1. • H-CeO 2 @GC delivered a high energy density with a high power density. • H-CeO 2 @GC exhibited an excellent cycling stability. Abstract 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 CeO 2 nanospheres conformally coated with graphitic carbon (H-CeO 2 @GC) via a facile hydrothermal method as a kind of electrode materials of supercapacitors. The as-prepared H-CeO 2 @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 CeO 2 (∼10 nm) conformally encapsulated in ultra-thin graphitic carbon layers. When applied in supercapacitors, the H-CeO 2 @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. [ABSTRACT FROM AUTHOR]

• The photocurrent density of WO 3 /RGO/Ni:FeOOH increased by a factor of 2.05. • The onset potential of WO 3 /RGO/Ni:FeOOH negatively shifted 83 mV. • Ni:FeOOH acts as a bi-functional modifier. • Ni:FeOOH improves light absorption and charge transfer process. • RGO as a conductive bridge-linker promote charge separation. The instability and low activity of WO 3 is the hot-topic for photoelectrochemical (PEC) water splitting, which is decreased by a sluggish interfacial kinetics and incomplete water oxidation. Aiming at such issues, we designed a ternary WO 3 /RGO/Ni:FeOOH photoanode, which exhibits 2.05 times larger photocurrent (1.32 mA cm−2) than the WO 3 NFs in 0.5 M Na 2 SO 4 electrolyte solution, accompanied with 83 mV cathodic shift of onset potential. These results demonstrates PEC response can occurs only in Ni:FeOOH but not FeOOH. Therefore, Ni:FeOOH acting as bi-functional modifier, can not only increase light absorption but also promote charge transfer process by forming p-n heterojunction with the WO 3 NFs. Besides, RGO forming a continuously conducting network can further improve charge separation process. Owing to their synergistic effects, the Faradaic efficiency and stability are both improved compared to its counterparts and the bare WO 3 NFs. This work may inspire the PEC application in other co-catalyst decorated systems. [ABSTRACT FROM AUTHOR]