Faradaic electrode-driven interfacial charge transfer for direct-current droplet generators

The droplet-based electricity generator (DEG) has attracted considerable interest as a sustainable and green energy-harvesting technology. Nonetheless, its low power density and alternating-current output have significantly impeded its practical integration into energy storage and power supply systems. Herein, we present a DEG architecture incorporating an additional Faradaic electrode (FE) that floats on the active polytetrafluoroethylene (PTFE) surface. The FE induces a Faradaic reaction between the water droplet and the electrode material before the droplet reaches the active PTFE surface. The FE-assisted DEG (FE-DEG) dramatically enhances charge-generation performance with direct-current (DC) output. Utilizing a double charge-generation electrode design, the FE-DEG achieved a maximum charge of 32.25 nC per droplet. Notably, the device exhibited 87.5% output retention after 1 h of testing, owing to the synergistic integration of the FE and the top electrode, which mitigated performance degradation. To confirm the feasibility of a large-area DEG-based energy-harvesting system, a blade-array-type FE-DEG system was demonstrated and exhibited linear scalability with the number of PTFE blade arrays. Moreover, the dual charge-collection mechanism, using both the FE and top electrodes, yielded a two-fold increase in total charge output of 7.79 μC in 60 s. Therefore, this FE architecture provides fundamental insights into a novel mechanism for charge exchange between water droplets and metal, paving the way for promising advancements in energy conversion.