Tuning the pore structure of N/O co-doped porous carbon nanosheets for high-performance supercapacitors and zinc-ion capacitors

Effective and straightforward synthesis of porous carbon nanosheets with tunable pore structures is crucial for advancing zinc ion hybrid capacitors (ZICs), owing to their superior ion transport and adsorption/desorption capabilities. In this study, nitrogen and oxygen co-doped porous carbon nanosheets were successfully synthesized from coal tar pitch using "synergistic pore formation" and "gas-assisted exfoliation" mechanisms. The utilization of dual activators facilitates the development of a hierarchically structured porous network with enhanced porosity across multiple scales. The obtained N/O co-doped porous carbon nanosheets possess a significantly enhanced specific surface area, an increased average pore diameter, and an expanded micropore size, along with an optimized mesopore/macropore ratio. Furthermore, the materials display typical characteristics of amorphous carbon, characterized by a high density of defect structures. These improvements contribute to an optimal mass-specific capacitance of 295.5 F g- 1 at 0.5 A g- 1, with retention of 248.1 F g- 1 (83.93 %) at 20 A g- 1. The assembled ZIC achieves a maximum energy density of 118.7 Wh kg- 1 and an exceptional power density of 9188.8 W kg- 1 in a 2 M ZnSO4 electrolyte. Additionally, it demonstrates outstanding cycling stability, retaining 94.44 % of its initial capacitance after 12,000 cycles at 5 A g- 1. This work provides a simple and effective strategy for synthesizing porous carbon nanosheet materials with tunable pore structures from coal tar pitch, offering promising prospects in high-performance ZICs.