Harnessing Solar-Driven Photothermal Effect toward the Water–Energy Nexus

Producing affordable freshwater has been considered as a great societal challenge, and most conventional desalination technologies are usually accompanied with large energy consumption and thus struggle with the trade-off between water and energy, i.e., the water–energy nexus. In recent decades, the fast development of state-of-the-art photothermal materials has injected new vitality into the field of freshwater production, which can effectively harness abundant and clean solar energy via the photothermal effect to fulfill the blue dream of low-energy water purification/harvesting, so as to reconcile the water–energy nexus. Driven by the opportunities offered by photothermal materials, tremendous effort has been made to exploit diverse photothermal-assisted water purification/harvesting technologies. At this stage, it is imperative and important to review the recent progress and shed light on the future trend in this multidisciplinary field. Here, a brief introduction of the fundamental mechanism and design principle of photothermal materials is presented, and the emerging photothermal applications such as photothermal-assisted water evaporation, photothermal-assisted membrane distillation, photothermal-assisted crude oil cleanup, photothermal-enhanced photocatalysis, and photothermal-assisted water harvesting from air are summarized. Finally, the unsolved challenges and future perspectives in this field are emphasized. It is envisioned that this work will help arouse future research efforts to boost the development of solar-driven low-energy water purification/harvesting.