Entwined Vine-Inspired Polyvinyl Alcohol/Phytic Acid Hydrogel Yarns for Moisture-Induced Electricity Generation

Abstract

Hydrogel-based moisture-induced electricity generators (MEGs) capture ambient moisture to produce electricity, showing promise for distributed energy. However, traditional hydrogels suffer from limited ion supply and slow moisture absorption. Here, polyvinyl alcohol (PVA) was functionalized with phytic acid (PA), and coaxial-wound PVA/PA composite hydrogel yarn MEGs were fabricated via template-assisted molding with freeze–thaw. Results indicate that PA significantly enhances the moisture absorption capacity of the hydrogel matrix; under 97% relative humidity (RH), the PVA/PA absorption rate reaches 27.612%, approximately 5 times that of the pure PVA. The PVA/PA composite hydrogel yarn MEG exhibits humidity-dependent output and “fast charging, slow discharging” kinetic characteristics. A single unit (1 cm) maintains ∼0.6 V for over 166 h, with a short-circuit current of 11.55 μA and a maximum power density of 5.683 μW/cm2. Five units connected in series or parallel can achieve a voltage of 4.249 V or a current of 52.85 μA. Furthermore, the interaction region indicator (IRI) was used to visualize the weak interactions between different systems and water molecules. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations reveal that PA broadens the electrostatic potential distribution of the material, increasing the binding energy between the PVA/PA and H2O to −35.398 kcal/mol, thereby effectively promoting water molecule adsorption and proton dissociation. Overall, this study provides new insights into the design of high-performance moisture–electricity materials and the optimization of device structures while also laying a theoretical and experimental foundation for expanding the application of environmental energy harvesting technologies in ultralow-power electronics.