Highly transparent hydrogel-based condenser for solar vapor collection

Solar vapor collection has emerged as a reliable method for freshwater production. However, despite recent advancements, solar water purification remains in the early stages of interfacial water evaporation development. The challenges associated with achieving efficient vapor collection have hindered its progress toward practical applications. Here, we developed a hydrophilic hydrogel condenser with exceptional condensation performance and high transparency using a straightforward sol–gel deposition method, involving the evaporation and crystallization of polyvinyl alcohol (PVA). The resulting 2D PVA-glass and 3D PVA-polycarbonate (PC) condensers exhibited significantly higher transmittance compared to condensers without hydrogel coatings during solar vapor collection. Under 1 solar irradiation, the solar vapor collection rates of the PVA-glass and PVA-PC condensers reached 1.07 kg m⁻² h⁻¹ and (93 % of the evaporation rate) and 0.71 kg m⁻² h⁻¹ (67 % of the evaporation rate), respectively. We combined the 2D PVA-glass and the 3D PVA-PC condensers with the evaporator for outdoor tests. The solar vapor collection rate remains good and the water production can meet people's daily water demand (PVA-glass: 6.75 L m⁻² d⁻¹, PVA-PC: 4.2 L m⁻² d⁻¹). The preceding applications proved great condensation effects and established a robust verification basis for future solar water purification.