Enhancement of output charge density of TENG in high humidity by water molecules induced self-polarization effect on dielectric polymers

Although utilizing charge excitation is an effective strategy to achieve high charge density for triboelectric nanogenerators (TENGs), the conductive pathways formed by water molecules in a high-humidity environment cause inevitable output charge decay and limit practical applications of TENGs. Herein, a self-polarization effect-based charge-excitation TENG (SP-CE-TENG) is proposed with high surface charge density (SCD), and the charge self-increase phenomenon of dielectric materials with different strong polar groups is investigated. It is found that the unique strong polarization characteristics of water molecules further promote the self-polarization process of dielectric materials with the increase in humidity. As a result, an ultra-high SCD of 2.88 mC m -2 is obtained in the atmosphere with 40% relative humidity (RH) using 7 µm homemade poly(vinylidene fluoride-trifluoroethylene) film. Meanwhile, the effective SCD of the SP-CE-TENG maintains more than 1.92 mC m −2 even at 90% RH, which is the highest charge density for TENGs in a high humidity environment. This work presents a practical approach to boosting the output charge density of TENGs, which is helpful for in-depth exploration of the polarization behaviors of polar molecules in a high-humidity environment. High surface charge density on dielectric polymers is achieved by water molecules induced self-polarization effect in strong electric field. It is found that the formation of hydrogen bonds between the -OH group in water molecule and the electronegative group (-F, etc) in dielectric enhance self-polarization effect of polar dielectrics. • The self-polarization effect of polar materials with different strong polar groups and the enhancement mechanism of high humidity on self-polarization were systematically studied. • Hydrogen bonds' unique strong polarization characteristics further promote dielectric materials' self-polarization process with increased humidity. • The surface charge density of SP-CE-TENG always maintains more than 1.92 mC m −2 even at 90% RH, which is the highest charge density for TENGs in a high humidity environment.