Materials for solar-powered water evaporation

Materials engineering enables the control of water-material interactions in solar vapour generators, which aim to efficiently utilize solar energy for the cost-effective production of clean water. This Review discusses material-design principles for solar evaporators, spanning from macrostructures to molecular configurations. Solar-powered water evaporation - the extraction of vapour from liquid water using solar energy - provides the basis for the development of eco-friendly and cost-effective freshwater production. Liquid water consumes and carries energy, and, thus, plays an essential role in this process. As such, extensive experimental and theoretical studies have been focused on water management to achieve efficient solar vapour generation. Many innovative materials have been proposed to enable highly controllable and efficient solar-to-thermal energy conversion to address the challenges in the energy-water nexus from the microscale to the molecular level. In this Review, we summarize the fundamental principles of materials design for efficient solar-to-thermal energy conversion and vapour generation. We discuss how to integrate photothermal materials, nanostructures/microstructures and water-material interactions to improve the performance of the evaporation system via in situ utilization of solar energy. Focusing on materials science and engineering, we overview the key challenges and opportunities for nanostructured and microstructured materials in both fundamental research and practical water-purification applications.