Hierarchical Pore-Gradient Silica Aerogel Balancing Heat and Water Management for Efficient Solar-Driven Water Evaporation

Efficient heat and water management are two essential aspects for enhancing solar-driven water evaporation. Here, an efficient strategy to synchronously achieve desired heat and water management based on hierarchical poregradient silica aerogel (HPSA) support that consists of large-pores at top regions, small-pores at bottom regions, and a porous wall constructed by mesoporous silica nanoparticles is demonstrated. The small-pores at bottom regions enable capillary pumping capability, while the large-pores at the top regions strengthen light capture and facilitate water/vapor transport. Additionally, the random distribution of super-large pores and the porous wall further promote water supply and diffusion. The unique nanostructure enables the conceived HPSA to show desirable advantages of minimized heat loss, fast water transport, and reduced water evaporation enthalpy. After coating with the photothermal material of carbon dots/polydopamine, a high evaporation rate of 1.95 kg m(-2) h(-1) under 1 sun is achieved for the HPSA evaporator, which exhibits significant superiority in promoting solar-driven water evaporation efficiency compared to a balsa wood and melamine sponge evaporator. In addition, the designed HPSA evaporator presents high recyclability and excellent salt resistance capacity in high-salinity brine (15 wt%), holding great promise for practical solar-driven water evaporation applications.