Recent advances and rational design strategies of carbon dots towards highly efficient solar evaporation

Solar evaporation using photothermal materials is an environmentally friendly and feasible solution to overcome the water scarcity issue by utilizing the abundant solar energy source. Some key points for efficient solar-to-thermal energy conversion have been extensively studied. Among them, the advancement of solar absorber materials has emerged as an attractive research topic, owing to their potential to enhance the efficiency of solar to thermal conversion significantly. Recently, carbon dots (CDs) have attracted great interest for their applications in this field. CDs have many desirable properties, such as broad light absorption (200-800 nm), high photothermal conversion efficiency (more than 90%), tunable structure and surface functionalization, easy to produce and abundant raw materials that meet the requirements for this application. In this review, the integration of CDs into solar evaporation systems and recent advances in CD-based solar absorbers will be summarized and discussed. Before that, brief knowledge of carbon-based solar thermal evaporation, including its mechanism and strategies to improve the efficiency, is provided, followed by CDs' synthesis and tunable properties that can be optimized for this application. Finally, the challenges and perspectives of research for CD-based solar evaporation are proposed, for example, optimizing solar absorbers by decorating hydroxyl-rich CDs in 2D or 3D structures.