Janus-Structured Carbon-Based Water-Evaporation-Induced Generator for Efficient Blue Energy Harvesting and Marine Cathodic Protection

Abstract Water-evaporation-induced energy harvesting has emerged as a promising blue energy technology; however, widespread application is hindered by water-saturation-induced instability and limited functionality. Herein, a low-cost flexible Janus water-evaporation-induced generator (WIG) is fabricated via facile immersion and spray-coating methods. Ketjen carbon black with a high specific surface area (1196.76 m2/g) serves as a conductive filler, while the PVDF-modified asymmetric structure effectively suppresses overhydration and maintains a durable wet-dry gradient. After systematic optimization, the device achieves maximum outputs of 1.0 V and 557 μA in a 12 wt % NaCl solution, delivering a cumulative energy density of 1100.3 kJ m–2 L–1 and 267.23 J m–2 in deionized water and seawater, respectively. Assembled modules enable capacitor charging and the operation of low-power electronics. Furthermore, a self-powered cathodic protection system is established to sustain a current density of 400 μA cm–2 for 12 h, enabling efficient marine corrosion protection. This work demonstrates a scalable dual-functional WIG, providing valuable insights into the development of advanced multifunctional blue energy devices.