In Situ Carbonized Polyvinyl Alcohol (PVA) Sponge by a Dehydration Reaction for Solar-Driven Interfacial Evaporation

In this work, an in situ carbonization technique was employed using a dehydration reaction to construct an evaporator with a bilayer structure using polyvinyl alcohol (PVA) sponge as the raw material for solar-driven interfacial evaporation. Its top layer was uniformly covered with carbon species prepared from dehydration of the PVA sponge, which promoted light capture to warm water for steam generation. Meanwhile, its interconnected porous structure remained intact after carbonization of the PVA sponge and was accompanied by the presence of some oxygen-containing functional groups, which preserved its hydrophilicity. Furthermore, its bottom layer shared the micro-scale porous characteristic and favorable hydrophilicity of the pristine PVA sponge. The results illustrated that the prepared CS-3 evaporator was provided with remarkable evaporation performance, mirroring an evaporation rate of 1.38 kg m−2 h−1. Additionally, a stable evaporation rate at around 1.36 kg m−2 h−1 was observed during the 10-cycle test. More importantly, the water desalinated from seawater was drinkable, which met the World Health Organization (WHO) standard. Consequently, it can be concluded that the evaporator developed using in situ carbonization of PVA sponge possessed many development prospects in the field of seawater desalination.