Biomass-based N/P co-doped hierarchical porous carbon fabricated by a facile dual physico-chemical activation strategy for efficient capacitive deionization

The preparation of heteroatom-doped hierarchical porous carbons (HPCs) possessing both high-performance and cost-effective is advantageous for the advancement of capacitive deionization (CDI). Biomass, which is abundant and inexpensive, has been widely utilized as a precursor for carbon electrodes. However, the simple pyrolysis of a single biomass typically leads to insufficient porosity with narrow surface area, along with poor wettability and conductivity, thereby resulting in limited desalination performance. Therefore, we employ ammonium dihy-drogen phosphate (NH4H2PO4) and potassium carbonate (K2CO3) as chemical and physical activators, respec-tively, to co-activate lotus petiole (LP) for the preparation of N/P co-doped hierarchical porous carbon (NPHPC). In comparison with conventional single K2CO3 activation, NPHPC prepared through dual physico-chemical activation exhibits exceptional specific surface area (SBET, 2170.00 m2/g), excellent pore volume (Vpore, 1.16 cm3/g), outstanding mesoporosity (Vmeso/Vpore, 72.41 %), superior hydrophilic performance (contact angle: 39 degrees), high specific capacitance (221.86F/g), moderate N-doping (3.1 %) and P-doping (0.4 %). When assembled for desalination, the synthesized materials demonstrate a fabulous electroadsorption capacity of 21.85 mg/g together with notable cycling stability, highlighting their excellent application prospects. In summary, this work presents innovative ideas in proposing a facile synthesis of high-performance heteroatom-doped HPCs for CDI desalination.