Carbon dot-integrated hydrogel systems for solar-driven water evaporation and purification: materials design, mechanisms, and recent advances

Abstract

Water plays a pivotal role as a resource for ecological sustenance. Escalating concerns about water scarcity have intensified research and scientific focus on next-generation water-treatment methods. Solar-driven water purification offers a sustainable pathway to reclaim freshwater resources and alleviate shortages. This review paper critically examines carbon dot (CD)-integrated hydrogel systems for solar water evaporation, emphasizing materials design, photothermal mechanisms and recent performance advances. First, the mechanism of solar water evaporation is discussed, followed by the photothermal properties of carbon dots, thereby highlighting recent developments in carbon dot-based solar water evaporators. Next, the various characteristics of hydrogels including their photothermal properties are elaborated. While reviewing the advantages of hydrogel-based solar water evaporators as well as the synergistic effects of carbon dot (CD)-based hydrogel composites, the recent advancements in CD–hydrogel composites are also overviewed. The key points on challenges in achieving long-term durability, multi-functional pollutant removal and prevention of salt crystallization are summarized, along with recommended future research directions. Efficient energy confinement facilitated by solar vapor generation can progress with updated designs, which can turn out to be evolutionary towards sustainability.