Preparation And Photocatalytic Performance Of Layered Transition Metal Oxide/Reduced Graphene Oxide Nanocomposites

As a sp² hybrid 2D carbon material,graphene exhibits good electrical conductivity and extremely-large specific surface area,which make it can be acted as an additive to increase the transfer of photo-generated carries and to suppress the recombination of photo-generated electron-hole pairs.When various transition-metal oxide such as TiO₂,ZnO,and ZrO₂ etc,are recombined with graphene,the singular synergistic catalytic effect is revealed,and the catalytic performance and electrochemical performance of these semiconductor materials can be effectively regulated and improved.A number of protonated layered transition-metal oxides such as H₂Ti₄O₉,HTiNbO₅,HTiTaO₅ and HNb₃O₈ etc are typical semiconducting compound and are photocatalytically active.Doubtlessly,the recombination between layered transition-metal oxides and graphene is a significant work.In this research,the layered HTiNbO₅,HNb₃O₈,and HTiTaO₅ were used as the host,respectively,and the grapheme as a guest,three series of novel nanocomposites were prepared by using exfoliation-co-flocculation process,in which the layered transition-metal oxide and the grapheme were delaminated to generate the corresponding dispersed systems,and then the colloidal solution containing the exfoliated layered transition-metal oxides single layers was mixed with the colloidal suspension containing ultrathin graphene oxide（GO）nanosheets,followed by adding acid solution to flocculate,and further by reduction hydrothermally with hydrazine hydrate,thus the nanocomposites between exfoliated layered transition-metal oxide and reduced graphene oxide were afforded,resulting in an increase in the interlayer distance of the host layered transition-metal oxide,thus the the aggregation of layered transition-metal oxide nanosheets could be prevented to a certain extent.The structure and morphology were characterized by means of powder XRD,FT-IR,Raman spectroscopy,N₂ adsorption-desorption technique,TEM and SEM.Etc.The photo-absorption property of the nanocomposites was measured by using DR-UV-Vis technique.The catalytic performance of the nanocomposites for rhodamine B photo-degradation reaction was also investigated.Compared with the original layered transition-metal oxides,the nanocomposites are a class of porous materials,and exhibit a high surface area and a large pore volume.The macropores,mesopores as well as small mesopores co-exist in the composites,showing a multi-level pore structure.The exfoliation-co-flocculation process provides access to the surface of the layered transition-metal oxide nanosheets.The results of photo-absorption property and photocatalytic performance indicated that upon modifying the layered transition-metal oxides with graphene through the exfoliation-co-flocculation way,its visible light response was effectively enhanced,and its photo-catalytic activity was improved,in particular that under visible light irradiation.The photo-catalytic activity of the nanocomposites increased with increasing doping amount of graphene.