Ag/TiO₂ Plasmonic Membrane For Contaminated Seawater Desalination

The solar-enabled vapor conversion based on the photothermal effect of plasmonic nanostructures is an effective strategy to utilize solar energy for achieving seawater desalination.However,what cannot be ignored nowadays is the increasingly serious organic contaminations in the actual environment,which bring new challenges to the solar desalination applications.Therefore,the development of a novel material that can decontaminate the organic molecules during seawater desalination is the main goal of this paper.For this purpose,we designed a large-scaled Ag/TiO2 membrane with an efficient and broadband absorption of solar spectrum,and applied it in solar energy-driven desalination and photodecomposition at the same time.This material provides a promising approach to obtain fresh water directly from contaminated seawater under solar irradiation with high durability and favorable reusability advantages.In the first part,we synthesized Ag/TiO2 membrane and explored its optical absorption characters,solar desalination properties and photocatalytic activities.We first fabricated a two-side opened TiO2 NTs based membrane via elevating the voltage in the end of the anodization process;Ag NPs were then decorated onto the surface and whole wall of the nanotubes by performing a mild sequential chemical bath deposition(S-CBD)method in a solution containing glucose and silver ammonia.The results show that the decoration of Ag NPs can broaden the absorption spectrum of the membrane.The average absorption rate in the visible region is greater than 90%,and the absorption rate in the range of 200-2500 nm is close to 80%.During solar-enabled desalination process,the generation of Ag2O and AgCl thin layers around Ag NPs play an important role in stabilizing the Ag structure.The solar thermal efficiency reaches 82%at 6 kW m-2,and the removal rate of phenol pollution in seawater in 5 hours is over 90%,which suggesting a reliable and effective approach to obtain fresh water directly from contaminated seawater with solar irradiations.In the second part,the FDTD method was applied to explore the role of each component in the membrane.The data of SEM,XRD and XPS were used for optical modeling of the membrane.The simulation shows that the SPR effect of Ag NPs can greatly enhanced the intensity of local electric field.More importantly,more hot-spots are demonstrated to generate around the Ag NPs on TiO2 compared with the Ag NPs in vacuum.The functions of Ag2O and AgCl were also investigated by FDTD method.It is worth mentioned that we also analyzed the field intensity distribution of two Ag NPs along the X-axis for two special polarized lights(P polarization and S polarization)and obtained the field intensity distribution of non-polarized light(sunlight).