Nitrogen and oxygen co-doped hierarchical porous carbon for zinc-ion hybrid capacitor

Heteroatom-doped porous carbon materials have shown great potential in energy storage devices. In this paper, the mixture of potassium polyacrylate and polyacrylamide was freeze-dried to obtain a precursor, followed by a one-step carbonization method to prepare nitrogen oxygen co-doped hierarchical porous carbon (HPC). The superior electrochemical properties of HPC-4 electrode could be attributed to the synergistic effects of the three-dimensional (3D) interconnected hierarchical porous structure, high content of heteroatomic functional groups, and large specific surface area. The symmetrical supercapacitor assembled by two HPC-4 electrodes achieves an energy density of 21.13 Wh kg−1 (100 W kg−1). More interestingly, the Zn//ZnSO4//HPC-4 hybrid capacitor constructed by HPC-4 as the cathode, zinc foil as the anode, and 2 M ZnSO4 as the electrolyte achieved an outstanding capacitance of 282.81 F g−1 (125.69 mAh g−1), an ultra-high energy density of 100.56 Wh kg−1 (100 W kg−1) and excellent cycle performance. This work provides a simple method for preparing high-performance electrode for zinc-ion hybrid capacitors.