Solar-Driven Harvesting of Freshwater and Electricity Based on Three-Dimensional Hierarchical CuO@Cu Foam.

The integration of solar steam generation and the hydrovoltaic effect is a promising strategy for simultaneously solving water scarcity and energy crises. However, it is still a challenge to attain a high water evaporation rate and a strong output of electricity in a single device. Here, we report a three-dimensional (3D) hierarchical CuO@Cu foam for solar-driven harvesting of freshwater and electricity efficiently. The 3D CuO@Cu foam synthesized by chemical etching shows a rough surface and porous structure, making it have a hydrophilic surface, high light absorption performance, and excellent photothermal effect. For deionized water, the evaporation rate is as high as 3.03 kg m h; meanwhile, the output voltage is 0.37 V under 1 solar irradiation. For real seawater, the evaporation rate decreases to about 2.48 kg m h, the output voltage increases to 0.41 V, and the maximum output power density is 9.47 μW cm. Both the water evaporation and power generation performance are very competitive. Outdoor experiments demonstrate that the 3D hierarchical CuO@Cu foam can desalinate seawater, while generating electricity continuously.