Critical pathways of salt-resistant solar thermal desalination toward high-efficiency evaporation and seawater resource extraction

Solar thermal desalination is a promising low-carbon solution for alleviating the growing global scarcity of freshwater resources. In long-term desalination processes, salt precipitation occurring at the water-air interface can lead to device performance degradation and even operation termination because salt deposits obstruct solar absorption and seawater transport. To address this challenge, numerous anti-salt precipitation strategies have been proposed in recent years. However, the exploration of these strategies has usually been considered separately from evaporator performance enhancement, hindering the simultaneous achievement of high performance and operational sustainability. In this review, we systematically discuss the intrinsic mechanistic correlation between the desalination performance and anti-salt precipitation ability, and propose approaches for simultaneously achieving high efficiency and sustainability. We first conduct a comparative statistical analysis across representative solar evaporators, and identify the dominant salt-management pathways. Then, we reveal the mechanisms by which these strategies fundamentally regulate efficiency-determining factors such as heat localization, vapor escape continuity, and salinity-gradient back-diffusion. On the basis of the elucidated salt-management mechanisms, we identify practical pathways to enhance the device performance during long-term desalination. Finally, we highlight the emerging shift from passive precipitation prevention to active salinity-gradient energy utilization and value-added brine/salt recovery, thereby transforming desalination into an integrated resource- and energy-harvesting process. This framework provides mechanistic guidance for the rational design of next-generation solar thermal desalination systems with self-regulated precipitation dynamics, high thermodynamic efficiency, and cogeneration potential of freshwater and salt resource from seawater.