Oxygen-Rich Polymers as Highly Effective Positive Tribomaterials for Mechanical Energy Harvesting

Triboelectric nanogenerators (TENGs) are a potential solution to the depleted state of fossil fuels, on the condition that the energy conversion efficiency can be further improved. Tribomaterials are important not only for improving the output performance of TENGs but also for extending their applications. In this work, a poly-ϵ-caprolactone (PCL) electrospun membrane is proposed as a highly effective positive tribomaterial, paired with an expanded polytetrafluoroethylene (ePTFE) membrane, to fabricate TENGs (PCL/ePTFE TENGs). Compared with a widely used polyamide-6 (PA6)/ePTFE TENG, the output performance of the PCL/ePTFE TENG is enhanced by about 28%, indicating that PCL possesses a stronger electron-donating ability owing to the existence of oxygen-containing functional groups as electron donors. Furthermore, the PCL membrane is modified using poly(ethylene glycol) methyl ether (mPEG), which possesses more O atoms, by electrospinning (ES) and dip coating (DC). The results reveal that mPEG is very effective at improving the positive electron polarity of PCL. With the increase of mPEG content, the output performance increases by more than 40%, yielding a maximum power density of 115.83 W·m^-2. More polymers have been compared to confirm that many oxygen-rich polymers show excellent electron-donating abilities and act as highly efficient positive tribomaterials. This work also provides additional options for more effective positive tribomaterials.