Supersonically sprayed rGO/ZIF8 on nickel nanocone substrate for highly stable supercapacitor electrodes

Reduced graphene oxide (rGO) decorated with dodecahedral ZIF8 was prepared using an easy and cost-effective co-precipitation method and deposited over nickel nanocones by a scalable supersonic cold spraying technique. The structure and morphology of ZIF8 were retained even after post-annealing under argon at 500 °C. Cyclic voltammetry analyses confirmed the excellent electrochemical performance of the rGO/ZIF8 composite, attributed to the dodecahedral structure of ZIF8, high electrical conductivity of rGO, and the nanocone textured substrate. The hierarchical morphology of ZIF8, the rGO nanosheets, and the nanocones (Ni) was confirmed by scanning and transmission electron microscopy. A three-fold enhancement of the specific capacitance (336 F⋅g^‒1 at a current density of 1 A⋅g^‒1) and long-term cycling performance with 96% retention were achieved after 10,000 cycles. The rGO/ZIF8 Ni-nanocone samples exhibited a high specific energy, capacitance, rate capability, and superior stability in comparison to previously reported supercapacitor electrodes.