Potentially scalable fabrication of salt-rejection evaporator based on electrogenerated polypyrrole-coated nickel foam for efficient solar steam generation

Abstract Solar steam generation (SSG) is a green and sustainable way for desalination. Herein, we report for the first time the electrodeposition fabrication of bilayer photothermal material (named PPy-NF-PUS) for efficient desalination, which was prepared by electrodeposited polypyrrole on nickel foam (PPy-NF) as the upper layer for solar absorption and polyurethane sponge (PUS) as the lower layer for water pumping and thermally insulating. Taking advantages of superhydrophilic wettability, strong light absorption and the porous network structure of PPy-NF, in well combination with the low thermal conductivity and super-absorbent capacity of PUS, the PPy-NF-PUS shows excellent energy conversion efficiency of 82.18% under 1 sun irradiation. Moreover, the PPy-NF-PUS shows excellent salt-resistant performance, e.g., when salt was placed on the surface of the solar evaporator of PPy-NF-PUS, it could dissolve quickly. In addition, the PPy-NF-PUS was modified by composite coating to achieve a strong hydrophilic-oleophobic wettability. Such unique wettability endows the modified PPy-NF-PUS shows excellent oil-repellent performance. Besides, an outdoor water evaporation and collection device was designed, and the average evaporation rate of PPy-NF-PUS was 1.2562 kg m−2 h−1 under about 0.755 sun irradiation, thus showing great potential for practical application in SSG, by combination with its simple, potentially scalable fabrication process.