Preparation Of Mxene-based Composite Films And The Performance Of Water Interfacial Evaporation

The growing water demand has led to a rapid increase in the volume of global desalination.The water produced by evaporation is of high purity.The preparation of clean water by solar evaporation is considered to be one of the most attractive and easy to achieve solar thermal technologies.In the recently developed interface solar evaporation system,the light absorption device is placed on the water-air interface,so that only the air-liquid interface can be heated,which the photothermal efficiency is greatly improved..The core of solar steam generator is the development of photothermal conversion materials.In recent years,MXene has been proved to have unique and attractive photothermal conversion characteristics.MXene and its related composites can absorb sunlight effectively because of their excellent electromagnetic wave absorption capacity,which is a necessary prerequisite for their photothermal conversion.In this paper,MXene/PVDF photothermal conversion materials and MXene/Ni photothermal conversion materials were prepared by simple filtration method and immersion method.The morphologies of these two materials has been tested by SEM,XRD and EDS.The characteristics of interfacial evaporation of these two materials were studied,and the better materials were determined and further studied.Then,two kinds of photothermal conversion materials,MXene/Co-MOF-74/PVDF and MXene/dendritic Co/PVDF,were prepared by filtration method.The morphology and composition of the materials prepared by adding different quality Co-MOF-74 and dendritic Co were analyzed,and the solar absorptivity,water evaporation rate and seawater desalination were texted to study the interfacial evaporation properties of the materials.The results show that the water evaporation rate of MXene-5 prepared by filtrating5 m LMXene dispersion on PVDF membrane is the highest,up to 1.65 kg/(m~2·h).The MXene-5 sample was selected for cycle test,and the water evaporation rate of the sample changed to 1.53 kg/(m~2·h)after 5 cycles.The water evaporation rate of Ni foam 12prepared by immersing nickel foam in MXene dispersion for 12 h was the highest,reaching 2.23 kg/(m~2·h).Ni foam 12 sample was selected for cycle test.After 5 cycles,the water evaporation rate of the sample was 1.81 kg kg/(m~2·h),decreased by 18.8%.By comparing the micro-morphology and photothermal conversion properties of the two materials mentioned above,Ni foam 12 samples have better micro-morphology and higher water evaporation rate,but Ni foam 12 materials have poor stability and do not have good recycling ability.The MXene-5 material has relatively good cycle stability,and then improved on this basis to prepare materials with better photothermal conversion properties.Different samples were prepared by adding different quality Co-MOF-74 and dendritic Co to MXene solution.Among them,the water evaporation rate of Co-MOF 2.5with 2.5 mg was the highest,and the cycle stability test and seawater desalination test were carried out.The rate of water evaporation is 1.72 kg/(m~2·h)after 5 cycles.The water evaporation rate of Co 2.5 sample is still 1.76 kg/(m~2·h),is tested in artificial seawater,the concentrations of main ions in condensed water are all lower than the standards specified by WHO and EPA,which proves that the two materials have good desalination ability in seawater.