Self-floating aerogel composed of carbon nanotubes and ultralong hydroxyapatite nanowires for highly efficient solar energy-assisted water purification

Solar energy-driven water evaporation is a promising technique for clean water regeneration to tackle the world-wide water scarcity problem. Previous studies have revealed the important role of the bilayer structure in the solar energy-driven water evaporation, the top layer is the photothermal material, and the bottom porous material is used for water transportation and heat insulation. Herein, a new kind of the bilayer aerogel composed of hydrophilic ultralong hydroxyapatite (HAP) nanowire aergel and hydrophobic carbon nanotube (CNT) coating has been developed and demonstrated as a highly efficient self-floating evaporator for solar energy-driven photothermal water purification. The hydrophilic and highly porous HAP nanowire aerogel with a low thermal conductivity ensures excellent thermal management and high water evaporation rate, and the CNT coating layer enables highly efficient solar light absorption and energy conversion. With these structural merits, the as-prepared HAP/CNT bilayer aerogel has a high water evaporation rate of 1.34 kg m−2 h−1 and high water evaporation efficiency of 89.4% under solar light irradiation at a power density of 1 kW m−2. Additionally, the high-performance water purification function of the HAP/CNT bilayer aerogel is demonstrated by producing clean water from the actual seawater and simulated wastewater. The experimental results demonstrate the promising potential of the as-prepared HAP/CNT bilayer aerogel for high-performance solar energy-driven photothermal clean water regeneration.