Co/Zn synergistic catalysis: Carbon nanotubes wrapped N-doped porous carbon derived from MOF as electrode materials for supercapacitors

Abstract

The development of metal-organic framework (MOF)-derived porous carbon materials, specifically CoZn/NC, for supercapacitors is achieved through a one-step annealing process of the precursor ZIF-67@ZIF-8, which has a distinctive flower-like structure. The flower-like structure is formed under the influence of the introduced SO₄²⁻, which accelerates the nucleation of ZIF-67. This process enables the CoZn/NC material to combine the advantages of a balanced pore size distribution, a high specific surface area, and high nitrogen content. As a result, the electrical energy storage is improved and pseudocapacitance is introduced. Furthermore, characterization results indicate that moderate amounts of carbon nanotubes grow on the surface of the carbon material. This growth is facilitated by the catalysis of cobalt nanoparticles and the synergistic effects of zinc. These carbon nanotubes help form an excellent conductive network. Electrochemical tests reveal that the specific capacitance of the CoZn/NC carbon material reaches 324.1 F g⁻¹ at a current density of 0.5 A g⁻¹ and retains 98.8 % of its initial capacitance after 14000 cycles at 10 A g⁻¹. Additionally, the CoZn/NC material, when assembled into symmetrical capacitors, achieves an energy density of 16 Wh kg⁻¹ at a power density of 300.8 W kg⁻¹, surpassing the performance of most other electrode materials derived from MOF-based porous carbon reported in the literature.