Highly flexible and flame-retardant aramid nanofiber composite papers for energy harvesting

In recent years, polymer-based triboelectric nanogenerators (TENGs) have been increasingly applied in the field of flexible wearable electronics. However, the lack of flame retardancy of existing TENGs greatly limits their applications in extreme circumstances. Herein, an ultra-thin and highly flexible aramid nanofiber (ANF)/MXene(Ti3C2Tx)/Ni nanochain composite paper was prepared through vacuum-assisted filtration and freeze-drying technology. Owing to the synergistic effect between ANF and MXene, the composite paper not only possessed excellent mechanical properties, which were able to withstand over 10000 times its own weight, but also exhibited outstanding flame-retardant and controllable Joule heating capabilities. Moreover, the mechanical energy capture characteristics of the composite paper-based TENG were evaluated, resulting in the open-circuit voltage (55.6 V), short-circuit current (0.62 μA), and transferred charge quantity (25 µC). It also could enable self-powering as a wearable electronic device with an instantaneous power of 15.6 μW at the optimal external resistance of 10 MΩ. This work is intended to set TENG as safe energy harvesting devices for reducing fire hazards, and will provide a new strategy to broaden the application ranges of TENG.