Ionic Liquids-assisted Design And Enhanced Photocatalytic Performance Of FeVO₄-base Materials

Since twenty Century,environmental pollution and energy crisis have become increasingly serious.It is imperative to develop new clean energy.Among many renewable resources,solar energy as the inexhaustible,green and clean resources with board prospects has attracted worldwide attention.Photocatalytic technology is a new technology which can convert solar energy into chemical energy directly for energy conversion and environmental purification.Hence,photocatalytic technology is an effective way to realize environmental protection and energy saving at same time.The core of photocatalytic technology is photocatalyst.Nowadays,the development of novel photocatalysts with high efficiency and stability has become a hot topic in the field of photocatalysis.It is an effective strategy to develop a new type of highly efficient semiconductor photocatalyst by building a heterojunction system.In the work presented here,it was focused on the ionic liquids-assisted design synthesis and application of photocatalytic degradation based on FeVO₄ and its composite materials.Three novel photocatalytic materials?FeVO₄,g-C₃N₄/FeVO₄ and Ag₃VO₄/FeVO₄?were prepared by a simple and controllable method.The microstructure,morphology and optical properties of the above mentioned photocatalytic materials were determined by various characterization methods.The photocatalytic activity and stability of the above materials were investigated under visible light irradiation at the same time.The structure-activity relationship between the structure and photocatalytic activity of photocatalytic materials was studied.The corresponding photocatalytic mechanism was proposed.The concrete research contents are as follows:?1?The porous FeVO₄ nanorods were successfully synthesized through calcining precursor nanorods,which were obtained via a simple hydrothermal method in the presence of reactable metal ion-containing ionic liquid 1-octyl-3-methylimidazolium tetrachloride ferrate?III??[Omim]FeCl₄?.Based upon the characterization techniques of XRD,SEM,TEM,BET and DRS spectrum etc.,the internal structure and external morphology of as-prepared samples were determined,which indicated that the pure porous FeVO₄-IL nanorods with considerable specific surface area?255.83 m2/g?and uniform pore size?3-7 nm?were successfully synthesized.The FeVO₄-IL catalyst is a visible light responsive n type semiconductor with a band gap of 2.35 eV and has wide range of UV-Vis absorption spectra.Moreover,porous FeVO₄ nanorod employed as a heterogeneous photo-Fenton-like semiconductor catalyst exhibited enhanced photocatalytic activity for the degradation of tetracycline?TC?and rhodamine B?RhB?under visible light irradiation.The porous FeVO₄ nanorods synthesized in ionic liquid presented higher efficiency for RhB and TC degradation than the FeVO₄ which synthesized by using ferric chloride as iron source.It can demonstrate that the [Omim]FeCl4 played important roles as reactant and capping agent during synthesis course,leading a significant influence on the regulation of their structure and inner properties.A possible mechanism of the three-way of activating H₂O₂ and degradating pollutants in FeVO₄/H2O2 photocatalytic synergetic system has been discussed in detail.?2?The g-C₃N₄/FeVO₄ photocatalysts were successfully prepared by hydrothermal synthesis.Based upon the characterization techniques of XPS,FT-IR,SEM,TEM and DRS spectrum etc.,the internal structure and external morphology of as-prepared samples were determined,which indicated that FeVO₄ nanorods were uniformly distributed and attached to the surface of the g-C₃N₄,and the heterojunction structure formed at the contact interface.The optical absorption threshold of FeVO₄ was broadened via introducing of g-C₃N₄,and transport efficiency of photogenerated carriers was improved.The degradation efficiency?99.4%?of 20 wt% g-C₃N₄/FeVO₄ was highest for photocatalytic degradation RhB after reacting 6 h under visible light irradiation,while the degradation efficiency of g-C₃N₄ and FeVO₄ was 74.5% and 14.7%,respectively.The photocatalytic mechanism analysis indicated that the band of g-C₃N₄ and FeVO₄ matched well,which was favorable for the transmission and separation of photogenerated electron-hole pairs and leaded to the obvious increase on photocatalytic activity of g-C₃N₄/FeVO₄ catalysts.?3?The Ag₃VO₄/FeVO₄ photocatalysts were successfully prepared by in-situ growth method.Based upon the characterization techniques of XRD,XPS,SEM,TEM,DRS and PL spectrum etc.,the internal structure and external morphology of as-prepared samples were determined,which indicated that Ag₃VO₄ nanoparticles were uniformly distributed and attached to the surface of the FeVO₄,and the heterojunction structure formed at the contact interface.The optical absorption threshold of FeVO₄ was broadened via introducing of Ag₃VO₄,and transport efficiency of photogenerated carriers was improved.The degradation efficiency?99.7%?of 40 wt% Ag₃VO₄/FeVO₄ was highest for photocatalytic degradation RhB after reacting 6 h under visible light irradiation,while the degradation efficiency of Ag₃VO₄ was 59.4%.The photocatalytic mechanism analysis indicated that the band of Ag₃VO₄ and FeVO₄ matched well,which was favorable for the transmission and separation of photogenerated electron-hole pairs and leaded to the obvious increase on photocatalytic activity of Ag₃VO₄/FeVO₄ catalysts.