Electricity Generation with Sodium Alginate Hydrogel for Osmotic Energy Harvesting

Seawater covers 75% of the Earth’s surface, and it exists in nature as a vast resource. Harvesting energy from this tremendous resource provides a promising green approach to tackle the problem of electricity shortage. Herein, we develop a simple and effective ion-selective hydrogel membrane to harvest the osmotic energy from seawater and salt solutions at room temperature. Sodium alginate hydrogel, an ion-transport medium with numerous functional groups and a hierarchical porous structure, shows excellent ion-transport and ion-sieving capability in salt solutions. A single device can output a 0.16 V open-circuit voltage and 0.048 μW power in real seawater. Through a simple serial connection, the output voltage of the device can be further linearly improved to charge capacitors and thus light a light-emitting diode (LED) lamp. This research provides a new direction of material selection for hydrovoltaic electricity generation technology, which is conducive to expanding the practical applications of energy harvesting.