Design of direction-independent hydrovoltaic electricity generator based on all-foam asymmetric electrode

To obtain higher open-circuit voltage, metal sheets and carbon electrodes are often used to construct asymmetric electrodes of water evaporation generators. However, the metal sheets hinder water evaporation, limiting device performance. Herein, an all foam-structured asymmetric water evaporation generator independent of water evaporation direction is designed. ZIF-67 has been shown to effectively enhance the surface potential of foamed iron electrodes and provide Co²⁺ charge carriers for charge transfer. After combining the FI-based cathode with melamine foam and a composite carbon cloth anode to form the FI/ZIF67@CMF-MF-CC@CNTs type device, compared with the metal sheet electrode, the current density is increased by 300% up to 862 μA/cm² and the voltage is increased by 50% up to 782 mV. The optimal power density is 101 μW/cm². We also demonstrate present device in both energy harvesting and daily electronics, highlighting its potential for scalable energy utility.