Biomass-derived N/O co-doped meso-microporous carbon nanosheets for high performance zinc storage

The development of biomass-based porous carbon electrode material technology is of crucial significance to construct a sustainable carbon based energy material system. This work presents an N/O co-doped meso-microporous carbon nanosheets with tomato peel as a carbon source via a facile KOH activation strategy. A series of characterization results, such as TEM, XRD, Raman, XPS, etc., show that the resultant porous carbon possesses a developed hierarchical pore structure (specific surface area and pore volume of 2976.4 m² g⁻¹ and 1.63 cm³ g⁻¹, respectively), abundant graphitized microcrystals, co-doping of N and O heteroatoms and good hydrophilicity. The button-type zinc ion hybrid capacitor (ZIHSC) assembled by as-prepared porous carbon as the cathode, 2 mol L⁻¹ ZnSO₄ aqueous solution as the electrolyte and Zn foil as the anode exhibits a specific capacity of 181.2 mAh g⁻¹ at a current density of 0.1 A g⁻¹. When the current density is amplified by 500 times to 50 A g⁻¹, the specific capacity still maintains 79.9 mAh g⁻¹, demonstrating excellent rate performance. The maximum energy density and power density are up to 144.5 Wh kg⁻¹ and 40.7 kW kg⁻¹, respectively. This study provides technical support for the high-value utilization of low value biomass waste to prepare electrode materials.