Tuning The Interfacial Properties Of Polymeric Photothermal Membranes For Improving Solar-Driven Evaporation

Utilizing solar energy to produce clean water is a promising strategy to solve the current global water shortage.As an important way of using solar energy to produce clean water,solar distillation technology has gained extensive attention in recent years due to its advantages of eco-friendly and low cost.However,due to the high heat loss,the traditional bulk solar heating process usually leads to a low solar energy conversion efficiency.In recent years,the interfacial solar-driven steam generation technology has been rapidly developed in this field,due to its advantages of high energy conversion efficiency and fast water evaporation rate.The interfacial solar-driven steam generation technology utilizes the photothermal membranes to absorb solar energy and convert it into thermal energy to locally heat the water for improving the water evaporation rate and energy efficiency.As a crucial aspect of photothermal membranes,its interface properties have a critical influence on heating performance and possible surface fouling for their practical applications.In this thesis,by using polymeric photothermal materials and tuning their interface properties,the influence of the interface property of the photothermal film on the interface heating performance has been discussed.Meanwhile,zwitterionic photothermal hydrogels were prepared to improve the anti-fouling capability for photothermal material.The main research contents and results are as follows:（1）Interface properties of polymeric photothermal films on their interface heating performance were revealed.Polypyrrole（PPy）photothermal film was obtained on a smooth substrate via oxidizing polymerization.The surface roughness of the PPy films can be adjusted by tuning the polymerization reaction conditions,and surface functional groups were introduced via a chemical vapor deposition method by employing functionalized silanes.By investigating the wettability,interface heat transfer performance,and water evaporation rate of polypyrrole photothermal films with different surface roughness and chemistries,we explored the effect of the interface properties of the PPy photothermal films on the heating performance in the solar-driven water evaporation.The results show that increasing the surface roughness and introducing hydrophilic functional groups can improve the interfacial heating performance of the photothermal membranes.This research provides insights for designing a highly efficient interfacial heating system.（2）Anti-fouling zwitterionic photothermal hydrogel for improving solar-driven steam generation was developed.Zwitterionic photothermal hydrogels（PSBMA/r GO）were obtained by using methacryloyl ethyl sulfobetaine（SBMA）,N,N-methylenebisacrylamide（BIS）,and graphene oxide（GO）via thermal-initiated cross-linking,followed by the reduction of GO hydroiodic acid.The surface morphology,chemical composition,light absorption,and solar-driven water evaporation performance of the zwitterionic photothermal hydrogels were characterized.We showed that the zwitterionic photothermal hydrogel can achieve a water evaporation rate of 1.72 kg m^-2 h^-1.Furthermore,a high water evaporation rate can be maintained when treating brine with high salinity（7 wt%）with the zwitterionic photothermal hydrogel,which guarantees the long-term stability of the photothermal hydrogels for clean water production and effectively inhibits salt deposition in the steam generation process for photothermal materials.