Synthesis of cobalt silicate nanosheets with mesoporous structure and high surface area as the promising electrode for high-performing hybrid supercapacitor

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• Co 2 SiO 4 NSs with mesoporous structure and high surface area were prepared. • Co 2 SiO 4 NSs with active sites therefore accelerate kinetic process of electrode reaction. • Co 2 SiO 4 NSs electrode exhibits specific capacitance of 638 F g −1 (319 C g −1 ) at 0.5 A g −1 . • Co 2 SiO 4 //AC HSC achieves the specific capacitance of 571 mF cm −2 (799 mC cm −2 ) at 1 mA cm −2 . • Co 2 SiO 4 //AC HSC device shows the energy density of 1.55 Wh•m −2 at the power density of 1.75 W•m −2 . The construction of electrode materials with novel morphology and structure showing enhanced electrochemical properties have received great attention and always been a task full of challenges and opportunities. Herein, mesoporous cobalt silicate nanosheets (Co 2 SiO 4 NSs) with excellent electrochemical properties are firstly synthesized by the sacrificial template stÖber SiO 2 spheres. Thanks to the small diameter and high specific surface area (114 m 2 g −1 ), Co 2 SiO 4 NSs can supply abundant reactive sites where the electrochemical reaction occurs, therefore they can accelerate kinetic process for mass transfer and achieve satisfactory electrochemical performance. The Co 2 SiO 4 NSs show the specific capacitance of 638 F g −1 (319 C g −1 ) at the current density of 0.5 A g −1 , and the capacitance stability after 10000 cycles is 82 % of the initial value. The Co 2 SiO 4 //AC hybrid supercapacitor (Co 2 SiO 4 //AC HSC) comprising of Co 2 SiO 4 -3 NSs and activated carbon (AC) achieves the specific capacitance of 571 mF cm −2 (799 mC cm −2 , 81 F g −1 ) at 1 mA cm −2 , the capacitance retention of 92 % after 10000 cycles and the energy density of 1.55 Wh m −2 at the power density of 1.75 W m −2 . The device also can light the light emitting diode (LED) bulb in the practical application field. This work firstly presents the in-situ growth of mesoporous Co 2 SiO 4 NSs by sacrificial template stÖber SiO 2 spheres with noteworthy electrochemical property for high-performing HSC, which can be popularized to synthesize other transition metal silicates (TMSs) with improved electrochemical properties.