Siloxene-reduced graphene oxide composite hydrogel for supercapacitors

The electrochemical properties of graphene-based supercapacitor electrode materials are closely related to their architecture and chemical nature. Herein, the siloxene-reduced graphene oxide composite hydrogel (SGH) with modified three-dimensional (3D) hierarchical architecture and increased oxygen-containing functional groups are developed via intercalating small amount of layered siloxene between the reduced graphene oxide sheets by a one-step hydrothermal process. Siloxene serves as the "spacers" to form a three-dimensional structure with graphene, resulting in increased specific surface area. More importantly, siloxene is used to modify the surface chemical nature of graphene sheets by introducing additional oxygen-containing functional groups. The abundant oxygen-containing functional groups on SGH contribute to the pseudocapacitance and improve the wettability. Consequently, the proposed SGH exhibits a high specific capacitance of 520 F g(-1) at 1 A g(-1) in a three-electrode system in 1 M H2SO4 electrolyte, which can be maintained for 76.9% even as the discharging current density increases up to 100 A g(-1). Moreover, excellent stability is achieved for SGH with approximately 96.3% retention of the initial specific capacitance value after 15,000 cycles at a high current density of 50 A g(-1). Furthermore, the assembled symmetrical supercapacitor of SGH//SGH delivers a high energy density of 24.5 Wh kg(-1) at the power density of 399.6 W kg(-1). These imply that the siloxene-reduced graphene oxide composite hydrogel may be a promising electrode material for high-performance supercapacitors.