Electron Transfer Mechanism at the Ferroelectric Polymer/Metal Interface in Humid Environments

Ferroelectric polymer-based triboelectric nanogenerators hold significant potential for energy harvesting and sensing, yet their performance is severely compromised by environmental humidity. However, the coexistence of non-polar and polar phases in ferroelectric polymers complicates the electron transfer mechanism at solid-liquid-solid interfaces, making the microscopic electrification mechanism still unclear. Herein, this study reveals the atomic-scale mechanism by which water molecules influence the contact electrification at the α/β phase PVDF-Cu interface based on first-principles calculations. Results demonstrate that water molecules significantly regulate the direction and quantity of electron transfer through configuration reconstruction. At the α-phase interface, disordered water reduces polymer surface charge density by reversing charge transfer direction. Conversely, at the polar β-phase interface, the F-H hydrogen bonding and polarized charge distribution promote an ordered, polarized water layer. its compact electric double layer dominates charge distribution. Additionally, this research identifies the electron acceptor/donor in wet-state interfacial electron transfer and determines the relative position of water molecules in triboelectric series (H₂O < Cu < α-PVDF < β-PVDF). It also elucidates that the suppression of oxygen atom electron capture ability by hydrogen bond networks is the key mechanism leading to the positive tendency of water molecules. This work provides crucial theoretical foundations for optimizing ferroelectric devices in high humidity and prompts reevaluations of phenomena at solid-liquid-solid interfaces.