Ternary composite based on homogeneous Ni(OH)2 on graphene with Ag nanoparticles as nanospacers for efficient supercapacitor

In this study, a ternary composite consisting of Ag nanoparticles (NPs) embedded reduced graphene oxide (rGO) and Ni(OH)(2) have been synthesized through microwave-assisted reaction. In this system, the rGO serves as conductive substrate to support the Ni(OH)(2) and prevent the Ni(OH)(2) from restacking. Moreover, the Ag NPs anchored on rGO can create a nanoscale spacers between the rGO/Ni(OH)(2) sheets which avoids the pi-pi interaction between rGO substrates leading to further increase in surface area. In addition, the decoration of Ag NPs also can improve the electrical conductivity of the composites leading to better contact between rGO and Ni (OH)(2). As a result of the unique nanoarchitecture, the Ag-rGO/Ni(OH)(2) composite exhibits high specific capacitance of 1220 F/g at 1 A/g, which is much higher than that of pristine Ni(OH)(2) (588 F/g). Moreover, the ternary composite also shows superior capacitance retention and cycling stability up to 2000 cycles. Asymmetric supercapacitors based on Ag-rGO/Ni(OH)(2) electrode and the activated carbon are also assembled. The asymmetric supercapacitors have a maximum energy density of 41.2 Wh/kg at a power density of 375 W/kg with excellent cycling stability. The results indicate the importance of rational design and synthesis of Ag-rGO/Ni (OH)(2) for high-performance energy storages.