Metal-organic framework derived ZnSe@rGO nanocomposites and their application in supercapacitors

Supercapacitors，as a new type of energy storage device between traditional capacitors and secondary batteries，show broad application prospects in many fields. In this study，graphene oxide （GO） is prepared by the Hummers method，and ZIF-8 with a regular dodecahedral structure is grown in-situ. Then，the ZnSe@rGO nanocomposite is successfully prepared via the chemical vapor deposition （CVD） method. SEM images show that the ZnSe@rGO nanocomposite has a regular dodecahedral structure. ZnSe grows along a layer of yarn-like rGO surface and exhibits good crystallization performance. BET tests indicate that the specific surface area of ZnSe@rGO is 57.36 m²·g-1，which is larger than that of ZIF-8@GO. Electrochemical performance tests of the samples show that，in 3 mol·L-1 KOH solution，the ZnSe@rGO nanocomposite has a high specific capacitance of 971.4 F·g-1 at a current density of 1 A·g-1，confirming the material has good pseudocapacitive behavior. Moreover，at a current density of 2 A·g-1，the ZnSe@rGO nanocomposite still maintains 74.49% of its initial capacitance and nearly 100% Coulombic efficiency after 5000 cycles，demonstrating excellent cycling stability. When assembled into an asymmetric supercapacitor （ZnSe@rGO∥AC），the device achieves a specific capacitance of 112.5 F·g-1 at a current density of 1.0 A·g-1. It also delivers an energy density of 40.0 Wh·kg-1 at a power density of 2057.1 W·kg-1，making ZnSe@rGO a promising candidate material for asymmetric supercapacitors.