Defect-rich N, S Co-doped porous carbon with hierarchical channel network for ultrafast capacitive deionization

Developing an eco-friendly and effective approach for preparing N, S co-doped hierarchical porous carbons (NSHPC) for capacitive deionization (CDI) is a huge task for desalination. Herein, NSHPC_SKK with interconnected hierarchical pore structures, manufactured via self-activation/co-activation of sodium lignosulfonate (SLS) encapsulation using KNO₃-KHCO₃ activators, inducing N, S co-doping. Different from NSHPC_S and NSHPC_SK, NSHPC_SKK exhibits the highest specific surface area (S_BET, 2264.67 m²/g) and a unique hierarchical pore structure (mesoporous volume/pore volume (V_meso/ V_pore), 0.65). Small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) both reveal the complex interconnected pore structure of NSHPC_SKK. Regional Raman imaging conjugated with XPS reveals the presence of extensively distributed N, S co-doped defect structures, providing NSHPC_SKK with excellent wettability and electrochemical performance. DFT calculations indicate that the N, S co-doping at the defect sites depicts excellent adsorption capability. Eventually, NSHPC_SKK acquired an impressive salt adsorption capacity (SAC) of 20.5 mg/g and the highest average salt adsorption rate (ASAR) of 12.1 mg/g/min, indicating its superior desalting performance. In-situ Raman spectroscopy confirms NSHPC_SKK's rapid ion regeneration mechanism. The research introduces a span-new NSHPC synthesis strategy for fabricating advanced NSHPC with rapid desalination response for upgrading CDI desalination.