Smart Energy–Harvesting Coating for Moisture–Droplets Based on Ionic Diodes and Transistor–Like Structures

The growing demand for distributed sustainable energy solutions has driven innovations in atmospheric moisture and droplet-enabled electricity generation. This study introduces a dual-mode moisture-droplet energy-harvesting coating (MDEC) that integrates a moisture electricity generator (MEG) and a triboelectric droplet electricity generator (DEG) into a single scalable coating system. By employing hybrid MXene-bridged graphene oxide (GO) microspheres as the hybrid ink electrode and a fluorocarbon resin dielectric layer, the developed MDEC overcomes the limitations of traditional metal-based electrodes that cannot be scaled for manufacturing and the inefficiency of single-energy harvesting schemes in moisture environments. The MEG component achieves a voltage output of 0.85 V at 25% relative humidity through ion concentration gradient diffusion, whereas the DEG component has a peak power density of 36 W m^-2 with a short-circuit current of 301 µA and an open-circuit voltage of 36.5 V. Modular integration of 360 units enables linear voltage scaling up to 301 V, successfully powering commercial LEDs and charging capacitor devices. This design offers a promising pathway for scalable low-power electronics and Internet of Things (IoT) applications.