High-efficiency capacitive deionization: Freestanding carbon electrodes derived from fungal hyphae with in-situ oriented MOF growth

High-performance electrode materials are critical for the development of the capacitive deionization (CDI) technology for efficient water desalination. In this study, binder-free porous carbon electrodes were successfully prepared from the fungal hyphae sheet with the formation and growth of metal-organic framework (MOF) crystals on the surface of hyphal fibers. The continuous fungal fibrous structure with abundant surface functional groups provided an ideal supporting substrate for in-situ oriented MOF growth. The MOF-fungal hyphae derived carbon (MOF-Fhy-C) exhibited an excellent property for CDI application, such as a large accessible surface area, excellent electrical conductivity, high porosity and hydrophilicity. The MOF-Fhy-C electrode achieved an outstanding CDI performance with a salt adsorption capacity of 40.8 mg/g and an average salt adsorption rate of 1.4 mg/(g·min) for treating 10 mmol/L NaCl solution at a cell voltage of 1.2 V, which are considerably higher than most of carbon-based electrodes reported in the literature. This research presents an effective strategy for fabricating freestanding CDI electrodes from fungal materials with MOF for high-performance desalination.