Solar-Driven Harvesting of Freshwater and Electricity Based on Three-Dimensional Hierarchical Cu2–xO@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 Cu_2-xO@Cu foam for solar-driven harvesting of freshwater and electricity efficiently. The 3D Cu_2-xO@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^-2 h^-1; 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^-2 h^-1, the output voltage increases to 0.41 V, and the maximum output power density is 9.47 μW cm^-2. Both the water evaporation and power generation performance are very competitive. Outdoor experiments demonstrate that the 3D hierarchical Cu_2-xO@Cu foam can desalinate seawater, while generating electricity continuously.