Gradient engineering in interfacial evaporation for water, energy, and mineral harvesting

The decarbonization of energy systems underscores the critical role of solar-driven interfacial evaporation (SDIE) in clean energy production. By leveraging solar energy to induce water evaporation, SDIE systems generate ion concentration, salinity, and temperature gradients that enable the co-production of water, green electricity, and valuable minerals. However, the performance and sustainability of SDIE co-production systems is restricted by a limited understanding of the underlying mechanisms that drive the formation of energy and mass gradients. In this perspective, we first outline the typical SDIE-based water-energy-mineral co-production (SWEM) systems. Next, based on material and system optimization, we propose rational strategies to enhance gradient formation through the regulation of energy and mass transfer processes, with the aim of strengthening the energy and resource output of SWEM. We also explore hybrid methodologies integrating multiple physical fields using gradient engineering, to achieve synergistic enhancements while mitigating gradient conflicts. Finally, we identify the current challenges and outline future directions for the development of next-generation SWEMs, aiming to enhance the sustainability and resilience of sustainable energy supply chains.