One-step hydrothermal preparation of TiO2/RGO/Ni(OH)2/NF electrode with high performance for supercapacitors

A facile one-step hydrothermal process is employed to synthesize a TiO2/RGO/Ni(OH)2 (reduced graphene oxide, RGO) composite on nickel foam (NF) by means of an in-situ growth route. In this case, NF acts as support, nickel source of Ni(OH)2, and supplement reductant of GO. For comparison, RGO nanosheets serve as nano-sized flexible support for connecting TiO2 and Ni(OH)2 blocks, which improves the electron transfer and alleviates the volume changes during the repeated charge/discharge process thanks to its high conductivity and mechanical properties. Besides, P25 (commercial TiO2 consisting of 80% anatase and 20% rutile) serves as TiO2 source, at different GO/P25 ratio of 1%, 2%, 5%, 10% and 20%. Electrochemical performances of TiO2/RGO/Ni(OH)2/NF electrode were evaluated by using cyclic voltammetry (CV), galvanostatic charge/discharge tests (GCD) and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. The TiO2/RGO/Ni(OH)2/NF electrode exhibited significantly enhanced capacitive performance when the weight ratio of GO/P25 was 10%. It delivered high capability of 4342 mF cm−2 at a current density of 5 mA cm−2 (374.3 F g−1 at 0.43 A g−1), and excellent charge-discharge cycling stability with 93.75% capacitance retention after 2000 cycles. An asymmetric supercapacitor (ASC) device consisting of this TiO2/RGO/Ni(OH)2/NF and an AC negative electrode was assembled.