Evaluating the Effect of Various Inner Surface Coatings on the Voltage Output of a Rain-Water Driven Tube Triboelectric Nanogenerator (TENG)

Triboelectric nanogenerators (TENGs) are increasingly studied as efficient, low-cost energy harvesting devices, making material optimization important for improving output. The purpose of this study was to evaluate the effect of three inner coating films, graphene, polytetrafluoroethylene (PTFE), and polyaniline (PANI), on voltage output in a TENG. It was hypothesized that the graphene coating combined with a hydrophobic spray would produce the highest voltage due to graphene's high electrical conductivity and surface charge retention, while the spray would reduce water adhesion to enhance charge transfer. Three tubes were modified with one of the inner coatings (PANI, graphene, or PTFE), while a fourth tube remained unmodified as the control. Each tube underwent 30 trials with alligator clips attached to a capacitor, and voltage was measured with a multimeter. The PANI group produced the highest mean voltage of 0.05930 V compared to graphene at 0.02617 V, a 126.6% increase. The control and PTFE groups produced lower outputs of 0.01153 V and 0.01730 V, respectively. Significant differences existed among coating groups, F(3,116) = 18.44, p < .001, with the graphene group showing high variability and multiple outliers, likely due to uneven spray coating and surface roughness. Additionally, the PANI group maintained more consistent performance. These results indicate that PANI coating enhances voltage output more effectively than graphene or PTFE, contrary to the hypothesis. This study demonstrates that coating type and fabrication method strongly influence voltage generation and provide a basis for further research on optimizing TENG fabrication.