PmPD@Fungi-derived monolithic carbon sponge as a high-capacity carbon electrode for desalination in flow-through capacitive deionization

Flow-through capacitive deionization (FT-CDI) is a promising technology for desalination due to its large-scale applicability and cost-effectiveness. However, binder-free monolithic carbon sponge (MCS) electrodes with robust structures, preferable permeability, and rapid electron transfer rate are desired to achieve high desalination performance. Herein, we developed a three-dimensional poly(m-phenylenediamine)@Fungi (PmPD@Fungi)-derived MCS (PMCS) by a simple strategy. The PmPD@Fungi monolithic sponge precursor was constructed using the cross-linked structure of fungi hypha as the skeleton based on its high aspect ratio. The NH2-rich PmPD layer served as a protective sheath and nitrogen source to be wrapped on the fungi surface by in situ polymerization. PMCS shows a superb CDI performance with an ion (Cl-) removal capacity of 11.82 mg g−1 due to its high-nitrogen content and optimized surface area, increasing by 162 % more than fungi-derived MCS (FMCS). Compared with FMCS, the electrical conductivity and compressive strength of PMCS were improved by 90 % and 27 %, respectively. The prepared PMCS electrode provides a promising alternative for FT-CDI towards future desalination technologies. •PMCS is a bind-free electrode readily prepared from the fungus suspension for CDI.•PmPD layer was a protective sheath to prevent rupture of hypha during calcination.•PMCS exhibits robust structure due to the support of PmPD-derived carbon layer.•The continuous and porous structure of PMCS enhances both electron and ion transfer.•PMCS with high N content shows a high desalination capacity of 11.82 mgCl g−1.