Bioinspired Hydrophilic-Hydrophobic Janus Composites for Highly Efficient Solar Steam Generation

Solar energy has received extensive attention as a renewable and sufficient energy source. Herein, inspired by the Janus wettability of lotus leaves, we have constructed a bioinspired hydrophilic-hydrophobic Janus hybrid system of carbonized carrot powder (CC powder)-modified cotton cloth with Nafion coating on one side (cotton cloth-NCC) for highly efficient solar steam generation. In cotton cloth-NCC, CC powder functions as a light absorber to achieve high light absorption, whereas the hydrophilic cotton cloth ensures efficient water transport. Meanwhile, the coating of Nafion establishes a hydrophobic-hydrophilic Janus structure, which can not only modulate water supply but also prevent salt deposition even with the high-concentration salt solution. The cotton cloth-NCC has been further shaped into a waved structure (w-cotton cloth-NCC) to increase the water evaporation area and achieve high light absorption (95%). Under 1 sun irradiation, w-cotton cloth-NCC yields a pure water steam generation rate of 1.88 kg m^-2 h^-1 and a seawater evaporation rate of 1.52 kg m^-2 h^-1. Furthermore, the w-cotton cloth-NCC also has a good purification effect on sewage: Escherichia coli can be completely removed, and the removal rate of Rhodamine B reaches 98.3%. The simple approach presented here for the construction of a high-efficient, low-cost, environmentally sustainable, long-term stable hydrophobic-hydrophilic Janus solar steam evaporator holds great promise for application in both environmental purification and photothermal conversion.