Controllable Nitrogen-Doped Hollow Carbon Nano-Cage Structures as Supercapacitor Electrode Materials

Supercapacitors (SCs) have garnered significant attention due to their high power density and long cycle life. Among the various electrode materials, carbon materials have emerged as a focal point of research owing to their superior conductivity, stability, and reproducibility. However, the relatively low specific capacitance and specific surface area of carbon materials result in suboptimal electrochemical performance, which seriously hinders their practical applications. This work introduces a straightforward yet effective strategy for constructing hollow nano-cage structures by tannic acid etching of ZIF-8. In this process, tannic acid releases protons that selectively etch the MOF structure, while the residual large molecules adhere to the ZIF-8 surface, stabilizing its framework and preventing structural collapse. Following high-temperature heat treatment, novel hollow nitrogen-doped carbon nano-cage structures (HNCs) are successfully synthesized. Electrochemical tests reveal that the material has a capacity of 349.3 F g−1 at a current density of 0.5 A g−1, and still has a coulombic efficiency of 97.61% as well as a capacity retention of 97.86% after cycling for 10,000 cycles at a current density of 3 A g−1. Therefore, this study provides a novel way to explore the application of carbon materials with excellent electrochemical performance for energy storage.