Minimizing enthalpy of evaporation in solar steam generation: An emerging strategy beyond theoretical evaporation limitation

Solar steam generation presents a promising solution to address water shortages in an eco-friendly and low-cost manner. Numerous broad-band light absorbers and topological designs have been developed to enhance the evaporation rate. However, when considering solely solar energy input, the evaporation rate faces theoretically limitations, assuming 100 % energy conversion efficiency, due to the latent heat requirement for water vaporization. As material selection and structural design reach the saturation of novelty, researchers are increasingly focusing on the enthalpy of evaporation of water (EEW). In this review, we briefly outline factors influencing net heat input, taking note of the influence of environmental energy, and then delve into the concept of EEW in evaporators, elucidating regulation principle, characterization and analysis methods related to EEW systematically. Subsequently, we review the latest research progress on optimization strategies aimed at minimizing EEW, including the modulation of hydration state and the adjustment of pore structure in evaporators. Finally, we discuss current challenges and future research opportunities in minimizing EEW in solar steam generation.