Integration of pore structure modulation and B, N co-doping for enhanced capacitance deionization of biomass-derived carbon

Biomass-derived carbon has demonstrated great potentials as advanced electrode for capacitive deionization (CDI), owing to good electroconductivity, easy availability, intrinsic pores/channels. However, conventional simple pyrolysis of biomass always generates inadequate porosity with limited surface area. Moreover, biomass-derived carbon also suffers from poor wettability and single physical adsorption of ions, resulting in limited desalination performance. Herein, pore structure optimization and element co-doping are integrated on banana peels (BP)-derived carbon to construct hierarchically porous and B, N co-doped carbon with large ions-accessible surface area. A unique expansion-activation (EA) strategy is proposed to modulate the porosity and specific surface area of carbon. Furthermore, B, N co-doping could increase the ions-accessible sites with improved hydrophilicity, and promote ions adsorption. Benefitting from the synergistic effect of hierarchical porosity and B, N co-doping, the resultant electrode manifest enhanced CDI performance for NaCl with large desalination capacity (29.5 mg g⁻¹), high salt adsorption rate (6.2 mg g⁻¹ min⁻¹), and versatile adsorption ability for other salts. Density functional theory reveals the enhanced deionization mechanism by pore and B, N co-doping. This work proposes a facile EA strategy for pore structure modulation of biomass-derived carbon, and demonstrates great potentials of integrating pore and heteroatoms-doping on constructing high-performance CDI electrode.