Hollow black TiAlO_x nanocomposites for solar thermal desalination

Although a solar-thermal conversion technique shows great potential for seawater desalination, there remains a grand challenge in exploring low-cost and high-efficiency photothermal materials. We report here a molten salt assisted galvanic replacement method for preparing a hollow black TiAlO_x composite, which features a high solar absorptivity with up to 90.2% and has a high efficiency of 71.1% in a high salinity solution containing 15.3 wt% NaCl (∼5 times more concentrated than seawater). We exemplify the practical application of such hollow black TiAlO_x composites as photothermal composites by setting up the automatic and manual tracking of solar desalination devices with a photic area of ∼1.0 m², which can produce purified water with a rate of above 4.0 L m^-2 day^-1 in high-salinity water under natural light irradiation, and maintains good stability upon 5 days of continuous running. The advantages of the as-developed hollow black TiAlO_x composites, including scalability, low cost, and high photothermal conversion efficiency, may open up a promising avenue practical application in seawater desalination.