Efficient Double-Layer Evaporators with Adjustable Pores for Sustainable Solar Evaporation.

Solar-driven desalination technology is currently an important way to obtain freshwater resources. Significantly, porous materials are used as substrate materials of interface solar evaporator, and their specific impact of water transport property and thermal management during evaporation is worth exploring. In this paper, poly(vinyl alcohol) (PVA) sponges were prepared by a chemical foaming method, adjusted the PVA polymerization degree, and formaldehyde-hydroxyl ratio to regulate the pore size, and polypyrrole (PPy) was grown in situ on the surface skeleton of PVA sponge to construct a new interfacial solar evaporator (PPy/PVA) with different pore structures. As the size of the evaporator pore changes, the trends in the water transport property and thermal management capability are opposite. Among them, the PPy/PVA-3 evaporator achieves a surface temperature of 38.9 °C and an evaporation rate of 1.764 kg m-2 h-1 under 1 Sun light. And the evaporation efficiency exceeds the theoretical limit (100%). This is because it has the optimal pore structure to balance the competition mechanism between the two aspects. At the same time, the evaporator exhibits good cyclability, stability, and self-cleaning capability. In addition, the evaporator has practical applicability with good purification of both organic dyes and seawater.