Photothermal Membrane Distillation toward Solar Water Production

Freshwater production is one of the biggest global challenges today. Though desalination can provide a climate-independent source of clean water, the process requires a high energy consumption. Emerging advancement of photothermal nanomaterials and the urgent demand for a green technology transition have reinvigorated the established solar distillation technology. The current development of photothermal vaporization focuses on material innovation and interfacial heating, which largely emphasizes vapor generation efficiency, without considering pragmatic water collection. Moreover, salt accumulation is another critical issue of seawater solar-driven vaporization. The incorporation of photothermal materials into a photothermal membrane distillation (PMD) solar evaporator design harmoniously resolves these issues through combination of renewable energy and efficient interfacial distillation, to achieve the ultimate goal of practical saline water into freshwater conversion. At this juncture, it is imperative to review the recent opportunities and progresses of the PMD system. Here, the fundamental photothermal processes, strategies for efficient evaporator design, evaluation of various criteria for photothermal material incorporation with desired properties, discussions on desalination, water treatment, and energy generation applications are covered. Guidelines in material and system designs to further advance the PMD system that is highly promising in delivering portable water for both large-scale and decentralized systems are provided.