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 cm 3 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.