Preparation Of Hollow Multi-shelled Structured Metal Oxide Semiconductor And Its Solar-Thermal Water Evaporation Property

Fresh water shortage is a global problem.Obtaining fresh water resources usually consumes electric or chemical energy.It is a promising direction to develop photothermal evaporation-condensate water purification which only depends on sunlight.The design of photothermal interfacial evaporation material is the key topic.Herein,from nano/micro structure and amorphous composites aspects amorphous Ta2Os/C hollow multi-shelled structure and CuO/Cu2O composite hollow multi-shelled structure are designed and prepared.The properties of the materials are discussed from three photothermal interfacial water evaporation control steps:solar absorption,photothermal conversion and water transport in hollow multi-shelled nano/micro structure,The structure-activity relationship between material composition,structure and water evaporation performance is established.It provides a valuable research basis for realizing efficient photothermal energy conversion and ultrafast interfacial photothermal water evaporation.Hollow multi-shelled structures(HoMSs)are a class of multi-level nanostructures with special morphology.It is an assembly structure of multiple nested cavities and relatively independent shells.HoMSs produces multiple scattering and enhanced absorption of incident sunlight.It has concentration effect on the heat.Moreover,the hierarchical pores with capillarity improve the diffusion and transmission rate of water/steam.The main research contents are as follows:(1)Amorphous Ta2Os/C-HoMSs were synthesized by sequential template approach(STA)from hydrothermal treated carbon spheres.In a tubular furnace,a series of amorphous Ta2Os/C-HoMSs with different composition and microstructure were prepared by adjusting the ratio and flow rate(oxygen partial pressure),heating rate and holding time of nitrogen oxygen mixture in calcination process.The corresponding amorphous tantalum oxide carbon composite triple shell hollow spheres(3s-Ta2Os/C-HoMSs)characteristic parameters are:HoMS diameter of about 900nm,shell thickness of about 25 nm,carbon amount of about 18 wt%,and amorphous revolving size of about 1.9 nm.(2)The prepared amorphous Ta2Os/C HoMSs were deposited on the absorbent cotton/insulating cotton three-dimensional structure substrate.Under the irradiation of one solar intensity,the ultrafast water evaporation rate of 4.02 kg m-2h-1 was obtained,and the rate did not decay for 30 days.In addition,under different application conditions such as seawater,sewage containing heavy metal ions,strong acid and alkali solution,it still maintains a high water evaporation rate.The obtained purified water meets the WTO drinking water standard.The experimental and simulation results show that the amorphous and multi-shelled structure of tantalum oxide can effectively enhance the light absorption;amorphous structure can effectively reduce the radiation transition and improve the photothermal conversion;the hollow multi shell structure has the ability of heat accumulation;the hierarchal pore structure provides a channel for the exchange of a variety of substances.At the same time,amorphization and carbon recombination modify the interaction between substrate and water molecules and reduce the slip resistance of water molecules diffusion;The nano pore structure regulates the aggregation form of water molecules,promotes the rapid evaporation of water molecules in the form of clusters,and reduces the actual evaporation enthalpy of water.(3)Expand the photothermal water steaming material to CuO/Cu2O HoMSs system.The results show that CuO/Cu2O HoMSs material has a photothermal evaporation rate of 3.2 kg m-2h-1 and a photo-vapor conversion efficiency of 92.8%under a simulated sunlight irradiation.In seawater and heavy metal solution,the water evaporation rate remains stable for a long time.On the other hand,copper oxide/cuprous oxide composite hollow multi shell structure can produce a large number of active hydroxyl radicals and superoxide radicals,which can effectively kill E.coli in the process of steaming water.In this paper,amorphous Ta2O5/C HoMSs and CuO/Cu2O composite HoMSs were prepared,and the synthesis method and material structure were comprehensively studied.Furthermore,the hollow multi-shell structured materials were applied to the field of interfacial photothermal evaporation.The energy conversion and material transfer law of photothermal evaporation process are studied by the combination of experiment and simulation.The structure-activity relationship between the hollow multi shell structure,composition and photothermal evaporation performance is established.And a preliminary exploration is made in the development of photothermal evaporation devices.