LAUSR

Abstract The in-situ N, S self-doped carbon nanosheets with hierarchical porous structure (NS-HPC) is prepared using l -cysteine as the source of C, N and S, and combination of NaCl template and KOH carbonization-activation process. The optimized sample exhibits high specific surface area (SSA) and possesses micro-, meso‑ and macro-pores, simultaneously. NS-HPC based supercapacitor electrode shows a significantly high gravimetric capacitance of 363.1 F g−1 and an excellent cyclic stability of 97.8% capacitance retention after 10,000 cycles in 6 M KOH electrolytes. The assembled symmetrical solid-state supercapacitor exhibits a remarkable energy density of 13.4 Wh kg−1 under 325 W kg−1 and still remains 8.1 Wh kg−1 at a high power density of 13 kW kg−1. Moreover, the as-obtained NS-HPC catalyst also displays an outstanding electrocatalytic activity for oxygen reduction reaction (ORR) with onset potential of 0.94 V, half-wave potential of 0.80 V and 4-electron pathway (n = 3.97) in 0.1 M KOH solution. Zinc-air battery assembled with NS-HPC delivers a high peak power density of 40.4 mW cm−2 and negligible potential loss after 200 cycles. This work provides an efficient approach to prepare heteroatom doped hierarchical porous carbon as multi-functional electrode materials for energy conversion systems.