Broadband solar-driven water evaporator based on organic hybrid bandgap and bio-mimetic interfaces

Abstract

Owing to the lightweight, flexibility, and molecular diversity, organic photothermal materials are considered promising solar absorbent materials for water-evaporating purification. Herein, we utilize the blend of two organic conjugated photothermal materials, PM6 and Y6, with broadband solar absorption from 350 to 1000 nm and high-efficiency photothermal properties to fabricate a Janus water evaporator on cellulose paper. Similar to the asymmetric wetting behavior on the lotus leaf, the evaporator shows efficient water adhesion on the bottom surface and water repellency on the top surface for a desirable self-floating capability and salt resistance. With a mass of only 0.5 mg per 3.14 cm2, the PM6:Y6 blend-based water evaporator achieves 88.9% of solar thermal conversion efficiency (η) and 1.52 kg m−2 h−1 of solar water evaporation rate (m) under 1.0 kW m−2 solar irradiation. These properties are almost the best performance among purely organic water evaporators especially with such a premise of material saving. The concentrations of primary ions are significantly decreased by 4–6 orders after desalination, accompanied by excellent performance for wastewater treatment. This evaporator realizes a m of 1.21 kg m−2 h−1, a η of 75.7%, and a voltage of 61 mV under one sun irradiation by assembling with a thermoelectric equipment. This study demonstrates that the blending of PM6 and Y6 achieves photothermal synergism, which improves the photothermal property and water evaporation rate, providing a valuable prospect for their application in water purification and thermoelectric power generation. (Figure presented.).