Preparation And Optical Properties Of Defective Molybdenum Oxide Nanobelts

Molybdenum oxide materials have excellent performance and broad development space in the fields of sensors,energy storage,electrochromism,photochromism,etc.due to their unique and diverse crystal structures and good optical and electrical properties.For the crystal structure of MoO3,there are currently three most common types:thermodynamically stable ?-MoO3,metastable structures ?-MoO3 and h-MoO3.The physical and chemical properties of MoO3 with various crystal structures are quite different.In addition,when introducing oxygen defects into the MoO3 nanostructures,it can be used as a new type of semiconductor plasma material and has important applications in the fields of drug delivery,tumor therapy,photothermal conversion,and photocatalysis.Here we conduct in-depth research on the synthesis of thermodynamically stable ?-MoO3 materials,study the light absorption characteristic of one dimensional(1D)plasmonic ?-MoO3-x nanobelts with regulatable oxygen defects from the aspects of material structure,morphology,element valence state,etc,realize the application of solar driven interface water evaporation.The specific research contents are as follows:(1)Thermodynamically stable ?-MoO3 nanobelts were prepared under hydrothermal conditions using metal molybdenum powder(Mo)as the molybdenum source.The experiment found that dissolving molybdenum powder in hydrogen peroxide solution(H2O2,30%)to obtain peroxymolybdic acid colloid as a precursor,the synthesized ?-MoO3 nanobelts reacted at 180? for 12 h own single phase,uniform size and good crystallinity.Based on this synthetic route,we have developed a surface-ligand protected reduction strategy to the synthesis of 1D defective MoO3-x nanobelts.1D MoO3-x nanobelts with various concentrations of oxygen vacancies are successfully obtained by simply increasing the amount of PEG-400 from 0 to 100,200.500 and 1000 ?L into the reaction system.The presence of PEG-400 plays two key roles in the formation of 1D defective MoO3-x nanobelts:it acts as the mild reductant to create tunable oxygen vacancies in the MoO3-x nanobelts and simultaneously as surface protected ligand to maintain the 1D morphology of MoO3-x nanobelts during the reduction process.The localized surface plasmon resonance(LSPR)effect caused by oxygen defects in MoO3-x nanobelts makes them own strong light absorption in the range of 200-2500 nm wavelength.(2)On the basis of the synthetic defective 1D MoO3-x nanobelts,using simple tools such as air-laid-paper(ALP),EPE foam,sand core suction filter,etc.,to prepare the MoO3-x nanobelts based interfacial water evaporator.Benefiting from the unique ID structure to ensure the formation of robust film on ALP,the assistance of the insulated EPE foam as a floatable thermal barrier layer,and strong light absorption in the full range of solar spectrum,we demonstrate that the 1D MoO3-x nanobelts can be used as an efficient photothermal film in the interfacial water evaporator.The MoO3-x nanobelts based interfacial water evaporator shows the optimal water evaporation rate of 0.99 kg·m-2·h-1 under one sun irradiation,which is 2.91 times than that of purewater,exhibiting the excellent performance in water evaporation.We believe the work opens a new avenue for designing defective semiconductor nanomaterials to enrich the photothermal conversion systems and their applications.