Hydrophobic LDH‐Tailored Exfoliated Graphene Sheet Energy Harvester: Harnessing Pressure‐Driven Heating and Electrolysis for Advanced Real Applications

Hydrovoltaic harvesting converts water-solid interactions into electricity, offering a sustainable power route across diverse settings. Yet most systems are hard to scale, suffer evaporation-limited lifetimes, and lack multifunctionality, limiting real-world application. To overcome these limitations, a highly optimized multifunctional hydrovoltaic harvester is developed by integrating exfoliated graphene oxide sheet (EGs) and hydrophobic layered double hydroxide (LDH) coatings onto a porous melamine foam scaffold. The porous foam ensures rapid, capillary-driven water transport, the EGs coating forms continuous conductive pathways, lowering device resistance to 600 Ω and enabling efficient electron transfer, and the hydrophobic LDH layer suppresses evaporation, sustaining stable energy generation for up to 37 h in seawater. This 250 cm³ device delivers 0.016 Wh-more than tenfold higher than previously reported multifunctional systems-demonstrating exceptional scalability. The harvester directly powers a water electrolysis cell, achieving continuous hydrogen evolution without external power. It also exhibits a unique pressure-responsive thermal sensing capability: mechanical loading (10-50 kPa) modulates internal resistance, producing localized Joule heating (50-70 °C) for self-powered thermal actuation. Integrates long-duration hydrovoltaic power, self-powered electrolysis, and pressure-induced thermal sensing in one device. Delivers durable, scalable, multifunctional performance for practical off-grid energy and responsive sensing.