N, S co-doped porous carbon derived from waste biomass enabling ultrafast storage kinetics for Zn-ion hybrid...

The performance enhancement of Zn-ion hybrid supercapacitors (ZIHSs) critically depends on the precise control of porous carbon's pore architecture and heteroatom arrangement. In this work, nitrogen/sulfur co-doped hierarchical porous carbon materials (2-N, S-LLPC) were synthesized from waste lotus leaves via a synergistic strategy encompassing N, S co-doping and potassium hydroxide activation. Material characterization demonstrated that 2-N, S-LLPC possesses a bimodal pore distribution, with a heteroatom content of 13.21 % (8.93 at% N and 4.28 at% S), where pyridinic-N and CSC groups serve as the predominant active sites. The 2-N, S-LLPC symmetric supercapacitors in 1 M Na₂SO₄ delivered 210 F g^-1 (0.4 A g^-1) with 340 Wh kg^-1 energy density. Furthermore, it exhibited excellent performance in ZIHSs: delivering a capacity of 191 mAh g^-1 at 0.5 A g^-1 while maintaining 93 mAh g^-1 at 20 A g^-1, alongside superior cycling stability. It achieves an energy density of 128 Wh kg^-1 at 151 W kg^-1, retaining 81 Wh kg^-1 even under 3118 W kg^-1. Ex-situ XPS analysis and DFT results confirmed that pyridinic-N and CSC groups facilitate reversible coordination with Zn²⁺. The solid-state ZIHSs device featuring flexible electrode design maintains stable electrochemical performance under mechanical deformation (e.g., bending and folding). When positioned horizontally, the device delivers a high energy density of 133 Wh kg^-1 at 101 W kg^-1, demonstrating substantial potential for practical energy storage applications. This work provides a biomass carbon doping strategy for advanced Zn-based energy storage.