Coupling of Hierarchical Al2O3/TiO2 Nanofibers into 3D Photothermal Aerogels Toward Simultaneous Water Evaporation and Purification

Serious freshwater shortage and environmental pollution boost the rapid development of solar-driven water production. Although improved evaporation rate has achieved in recent years, undesirable impurity (e.g., pollutant components) can also be inevitably evaporated and collected as impurity in produced freshwater. This work reports new ultra-light three-dimensional (3D) aerogels assembled by hierarchical Al2O3/TiO2 nanofibers and reduced graphene oxide (RGO) for exciting synchronized solar-driven evaporation and water purification. Hydrophilic Al2O3/TiO2 fibrous channels linked up the graphene hot-spots and water body for sufficient water supply and bulk water insulation. Meanwhile, featured with thermal insulation effect, the Al2O3/TiO2 nanofibers effectively locked the converted heat with less energy loss from sunlight. The introducing of Al2O3/TiO2 nanofibers into RGO aerogel led to the effective interfacial evaporation for a more rapid water evaporation rate (2.19 kg · m−2 · h−1, normalized to evaporation area including both top and side surface), which was 36% higher than that of pristine RGO aerogel. Moreover, simultaneous with the strong steam generation, Al2O3/TiO2 nanofibers in situ removed the pollutants within steam by photodegradation, achieving polluted wastewater purification with high contaminant removal ratio of 91.3%. Our work on coupling Al2O3/TiO2 nanofibers into photothermal aerogel provides attractive solutions for the challenges of clean water scarcity and serious environmental pollution.