Hydrangea-like NiMoO₄-Ag/rGO as Battery-type electrode for hybrid supercapacitors with superior stability

It is a great challenge to design electrode materials with good stability and high specific capacitance for supercapacitors. Herein, a three-dimensional (3D) hydrangea-like NiMoO₄ micro-architecture with Ag nanoparticles anchored on the surface has been designed by adding EDTA-2Na, which was assembled with reduced graphene oxide (rGO) and named as NiMoO₄-Ag/rGO composite. Benefiting from the synergetic contributions of structural and componential properties, NiMoO₄-Ag/rGO composite exhibits a high specific capacitance of 566.4 C g^-1 at 1 A g^-1, and great cycling performance with 90.5% capacitance retention after 1000 cycles at 10 A g^-1. The NiMoO₄-Ag/rGO electrode shows an enhanced cycling stability due to the two-dimensional towards two-dimensional (2D-2D) interface coupling between rGO and NiMoO₄ nanosheets, and the stable 3D hydrangea-like micro-architecture. Moreover, NiMoO₄-Ag/rGO with 5-15 nm pore structure and enhanced conductivity exhibits improved charge transfer and ions diffusion. Besides, NiMoO₄-Ag/rGO//AC capacitor displays an outstanding energy density of 40.98 Wh kg^-1 at 800 kW kg^-1, and an excellent cycling performance with 73.3% capacitance retention at 10 A g^-1 after 8000 cycles. The synthesis of NiMoO₄-Ag/rGO composite can provide an effective strategy to solve the poor electrochemical stability and slow electron/ion transfer of NiMoO₄ material as supercapacitors electrode.