Interfacial Engineering Of Two-dimensional Materials-based Aerogels And Their Application In Solar-driven Water Evaporators

With the fast development of economy,industry and living conditions,the human society is demanding more fresh water.However,the scarcity of fresh water on earth and the increasingly serious water pollutions have led to a more intense supply of drinkable water.The emerging solar-driven water evaporators have attracted worldwide attentions because they possess the advantages of simple preparation and maintenance,easy operation,and high energy conversion efficiency.The solar absorbing layer,i.e.,the photothermal porous material,is the core component of these devices,which functions as energy input and conversion,water vapor generation,etc.Recently,two-dimensional materials,such as graphene and MXene,are emerged as ideal photothermal materials due to their high specific surface aera,high solar absorption and conversion capacity.However,important issues in these materials,such as incomplete light absorption window in the full spectrum of solar light,serious self-stacking,and smooth surfaces（which are not conducive to water evaporation and transportation）,limit their practical applications in this field.In this essay,the interface engineering of two-dimensional materials（graphene and MXene）was conducted by different chemical processes and their composited aerogels were synthesized,whose structures-performance relationship were systematically studied.Furthermore,the solar-driven interfacial water evaporators were prepared based on the aerogels,and their evaporating behaviors were investigated.Finally,their applications in seawater desalination and wastewater treatment were explored.The main experimental results thus obtained include:（1）By performing surface modification on graphene（GO）,we synthesized Si C-r GO（reduced Graphene Oxide）composite aerogel,which effectively prevented GO nanoflakes from self-stacking and improved the porous structure.The introduce of Si C on r GO surface also promoted the nucleation and transport kinetics of water droplets in the aerogel;besides,the interfacial engineering kept the structural stability of sample.Therefore,the aerogel has its wide light absorption window together with high light absorption and photothermal conversion efficiency.The solar-driven water evaporation device based on the Si C-r GO composite aerogel possesses a water evaporation rate and a solar-water vapor conversion efficiency of 1.85 kg m^-2 h^-1 and 95%,respectively,under one solar irradiation;moreover,the device was able to maintain a good cycling stability and salt resistance in simulated seawater.Specifically,the quality of fresh water collected using the device is similar to that of domestic water.（2）We used chitosan（CS）,polydopamine（PDA）and Ag nanoparticles to modify the surface of MXene and synthesized CS-MXene-PDA-Ag（CMPA）aerogel.With the synergistic effect of materials and structures,the aerogel possesses a good light absorption and a high photothermal conversion efficiency.Moreover,the water evaporation rate and energy conversion efficiency for the solar-driven water evaporation device based on this aerogel were measured as 2.31 kg m^-2 h^-1 and 100%,respectively,under one sun illumination.The maximum efficiency of the device is attributed to its efficient management of ambient energy.Finally,the device has excellent stability and shows promising applications in seawater desalination and wastewater treatment.