Preparation And Application Of The Composite Films Of Graphene And TiO₂ Nanowires

Due to its unique optical,chemical,mechanical,thermal and electrical properties,graphene has received widespread attention.In practical applications,graphene and its derivatives are often loaded on the substrate or combined with other functional materials to form graphene based nanocomposite materials.At present,a variety of nano composite structures from graphene and semiconductors,metals as well as other inorganic nano materials have been fabricated,such as porous hydrogel structures,core-shell structures,and graphene based composite films(GCFs),etc.Among all kinds of semiconductor materials,titanium dioxide(TiO2)have been widely used because of its excellent photocatalysis,photoelectrochemical properties,environmental friendly and controllable morphology.The composite structure of TiO2 and graphene has the advantages of fast charge transfer,better electrocatalytic activity and structural/chemical stability,which can overcome the shortcomings of the two materials when they used alone in adsorption,photocatalysis and sensor applications.In this paper,we utilized TiO2 nanowires(TiO2 NWs)and graphene oxide(GO)to prepare graphene/TiO2 nanowires(rGO/TiO2 NWs)composite films,and explored the application of the films in adsorption and sensor.The main results are as follows:(1)The GO and TiO2 NWs were prepared by improved Hummer method and hydrothermal process respectively.The mixture of rGO and TiO2 NWs were treated by another hydrothermal process,and then the rGO/TiO2 NWs composite films were obtained by vacuum filtration of the mixtures after hydrothermal reaction.By adjusting the amount of TiO2 NWs in the mixture,different films of rGO/TiO2 NWs-25%,rGO/TiO2 NWs-40%,rGO/TiO2 NWs-50%,rGO/TiO2 NWs-70%and rGO/TiO2 NWs-80%were prepared.Their morphology and crystal structures were characterized by SEM,TEM,XRD and Raman spectroscopy.The adsorption experiments of Cu2+ showed that the maximum adsorption capacity of copper ions was 34.58 mg/g,demonstrating the potential ability of the film in water treatment.(2)The conductivity of the composite films were improved by heating in ammonia gas at 600? for 3 hours.After such treatment,the films were used as electrodes to load Pt nanoparticles by electrochemical deposition method.The performances of as-prepared electrodes for electrochemical detecting of H2O2 were studied.The results showed that rGO/TiO2 NWs-25%/Pt composite film electrode have the best sensing performance,exhibiting a linear detection range of 0.04?38mM,the sensitivity of 127.3uAmM-1cm-2 and the detection limit of 0.018mM.(3)The TiO2 NWs were prior modified by heating in ammonia gas at same condition to obtain nitrogen-doped TiO2 NWs-N.The TiO2 NWs-N was then composited with GO to prepare the rGO/TiO2 NWs-N-50%film and rGO/TiO2 NWs-N-25%/Pt film electrode.The photocatalytic experiment showed that rGO/TiO2 NWs-N-50%composite film presented larger photocatalytic activity for degradation of methylene blue(MLB)but reduced adsorption capacity,compared with rGO/TiO2 NWs-50%film.At the same time,rGO/TiO2 NWs-N-25%/Pt composite film electrode gave better H2O2 sensing performance compared with rGO/TiO2 NWs-25%/Pt,with the linear detection range of 0.02-42mM,the sensitivity of 212.8 uAmM-1Mn-2 and the detection limit of 0.011mM.These results reflected that the properties of TiO2 NWs could be improved more efficiently upon prior heating in ammonia gas,which was beneficial to the application of the composite film as a photocatalysis or electrode material.