Embedment of graphene in binder-free fungal hypha-based electrodes for enhanced membrane capacitive deionization

Freestanding carbon electrodes that do not use binders are suitable for realizing high-performance capacitive deionization (CDI). Herein, we developed a freestanding and binder-free electrode derived from the fungal hyphae of Aspergillus niger with embedded graphene (G-FhEld) or activated carbon (AC-FhEld) for CDI. The carbonized fungal hypha fibers provided a stable 3D carbon framework with a hierarchical structure, and the embedded graphene or AC increased the conductivity, specific surface area, and amount of adsorption sites of the electrodes. When used in CDI cycles for desalination, the G-FhEld exhibited a gravimetric electrosorption capacity of 32.3 +/- 1.7 mg/g and an average salt adsorption rate of 1.1 mg/(g center dot min) from low-salinity water (10 mM NaCl), outperforming AC-FhEld and the electrodes without graphene or AC. These values were considerably higher than those of most existing carbon electrodes. Fungal hyphae can be mass-produced from food waste and separated by simple filtration to prepare the precursors of the electrodes, and thus, G-FhEld is highly scalable for large-scale CDI applications. This research presents a facile, effective, and low-cost technique to fabricate carbon electrodes to realize enhanced desalination by CDI.

Automated summary

In this research, a freestanding and binder-free carbon electrode was developed by embedding graphene or activated carbon in the carbonized fungal hypha fibers. The embedded graphene electrode exhibited higher gravimetric electrosorption capacity and salt adsorption rate compared to the activated carbon electrode. The use of fungal hyphae derived from food waste makes the electrode fabrication technique highly scalable for large-scale capacitive deionization (CDI) applications.