High-efficiency evaporation induced electricity generation of wood in seawater

Hydrovoltaic technology, especially the power generation driven by natural evaporation of water, has great potential for sustainable development, but its performance may degenerate significantly in seawater. Here, we find that sulfonated natural woods can generate power even more efficient by evaporation of seawater than deionized water. A single sulfonated maple device yields potential of 0.97 V with power density of 15.5 μW cm⁻² through evaporation of seawater, in comparing to the yield of 0.77 V and power of 6.2 μW cm⁻² through deionized water, one order higher than the best reported performance in saline-environment. Integration of four such units in series and parallel yields voltage of 2.3 V and current of 2.6 mA, respectively. It is revealed that sodium ion-wood interactions and the coupling between capillary-driven flow and ion transport are the root for the induced electricity. The power generation can maintain stable over 100 h when the wood sample is washed by fresh or rainwater periodically. It is also interesting that once wetted in seawater, the wood sample can produce power stably over 7 h in air. Since the ocean covers 70% of the earth's surface and absorbs a large amount of solar energy through evaporation, this discovery is particularly promising.