Influence of solution chemistry on liquid-solid triboelectric charging of PTFE

Droplet-based TriboElectric NanoGenerators (TENGs) offer a simple and environmentally friendly way to convert liquid motion into electrical energy, yet the mechanisms that govern liquid–solid triboelectrification are still not fully understood. In particular, the role of solution chemistry in controlling charge generation remains unclear. In this work, we examine how pH, ionic strength, and molecular composition influence triboelectric charging when liquid droplets interact with a polytetrafluoroethylene (PTFE) surface in a controlled droplet-based TENG. Charge–time measurements were performed using acidic (acetic acid), basic (sodium acetate), mixed buffer, and ethanol–water solutions over a wide range of concentrations. Across all systems, increasing solute concentration reduced the magnitude of the accumulated charge. In electrolyte solutions, this suppression is consistent with enhanced interfacial screening, while in ethanol–water mixtures it arises from changes in dielectric properties and interfacial water structure. Acidic droplets exhibited a brief polarity reversal prior to reaching a negative steady‑state plateau, suggesting that short‑lived proton enrichment temporarily competes with electron transfer at early contact times. Overall, the results are most consistent with the mechanism of the contribution aligns most closely with electron transfer; however, electrokinetic contributions cannot be excluded. More experiments are needed to confirm the contribution mechanism.