Droplet electricity generation via biogenic iron nanoparticle-coated fungal bulking sludge

Discharged fungal bulking sludge (FBS) is a byproduct of wastewater treatment processes, due to high costs and environmental contamination. This study proposes a novel design, biosynthesized iron nanoparticles (FeNPs) on the surface of fungal biofilm, for simultaneous generating electricity with the action of a single water droplet. The output performances of electric energy were achieved, with an instant voltage of 40 mV. The hydrophily and pore structure of fungal biofilm contributes to the dragging force of water droplets. The electricity generation of the devices depends on electron transfer at long distance due to the conductivity of FeNPs. The stimulation model of hydroelectric power generation demonstrated that electric potential attributed to the asymmetric proton concentration gradient. Batch experiments demonstrated that protonation and ionic dynamics were crucial for electricity generation. This study is the first to utilize non-electroactive fungal biofilm to biosynthesize iron nanoparticles on their surface for energy conversion, achieving a stable and continuous power output with the action of the movement and dissociation of water molecules within the porous structure of the biofilm. These discoveries offer new ideas for the development of novel energy materials and technologies in the crossing field between wastewater treatment and water-based power generation.