Fabrication And Photocatalytic Performance Of Nano-TiO₂/graphene Foam Composites

In the 21 st century,the contradiction between development and environment increasingly prominent,and the research of using of photocatalysis to protect enrivonment gradually increases,especially the photodegradation of organic pollutants in wastewater has become one of the most popular research topics.TiO₂,as an economic environmental-friendly material,has very high photocatalytic performance,and recently has attracted more and more attention of researchers.However,TiO₂ forbidden band width is larger?rutile phase is 3.0 eV,anatase phase is 3.2 eV?,can only be excited by the ultraviolet light,serious limits its catalytic activity and the practical application;the other hand,when TiO₂ is irradiated,the excited electron hole pairs cannot migrate to the surface in time,quickly recombine inside,cannot play the catalytic effect,also reduce its catalytic activity.Therefore,this article from the perspective of TiO₂ structure design consideration,hope that through nanocrystallizating,greatly shorten the carrier migration path,reduce composite risk,improve the TiO₂ photocatalytic efficiency.In addition,graphene as a single atomic layer of carbon nanomaterials,has excellent electrical properties and is a good electron acceptor.At the same time,the three-dimensional foam structure of graphene has a great specific surface area and strong adsorption capability.Therefore,the introduction of graphene into the photodegradation field,through the controllable combination with TiO₂,can effectively make up for the deficiency of TiO₂,and greatly improve the photocatalytic performance of the new structure.Through the design and fabrication of nanometer TiO₂/graphene foam composite structure,and can effectively shorten the light excites the carrier to the migration path on the material surface,reduce the internal recombination lead to low efficiency;Rapid separation of excited electrons and holes using graphene ultrahigh carrier mobility,participation in organic molecular decomposition reactions,improved catalytic efficiency;The graphene foam with the ultrahigh specific surface area can effectively adsorb the organic molecules in the wastewater,which is beneficial to the photocatalytic reaction.In addition,graphene foam has a certain mechanical strength,can be used as a support to facilitate the overall recycling.Based on the above analysis,this paper mainly studies the controllable fabrication of TiO₂ nanowires,the controllable fabrication of nanometer TiO₂/graphene composite structures,and the photocatalytic performance of TiO₂ nanowires.The main work content and results are summarized as follows:The large diameter of TiO₂ nanowires have been prepared by two-step hydrothermal method.The effects of The first step alkali hydrothermal process and The second step alkali acid hydrothermal process parameters on the microstructure and photocatalytic properties of the samples were investigated by means of SEM,XRD and Raman.Alkali hydrothermal temperature is 200 ?,reaction time is 12 h,10 M NaOH under the optimum reaction conditions to obtain the sample morphology for the large diameter ratio nanowires,and the phase is pure anatase phase TiO₂.Through photodegradation experiments it was found that the photocatalytic performance of the samples related to its morphology,the sample with large diameter ratio showed higher photocatalytic activity,passing 30 min uv radiation,photodegradation efficiency reached 95%.The addition of ethylene glycol gave a large diameter ratio nanowire at a lower basicity of 3 M NaOH.The effects of the addition and reaction temperature of ethylene glycol on the micromorphology and photocatalytic properties of the samples were investigated.Adding ethylene glycol to sample in the first step hydrothermal process directly get the anatase TiO₂,When the amount of ethylene glycol was less,the sample was mixed with H2Ti3O7 and anatase TiO₂.adding amount was 50%,have pure anatase phase.The addition of ethylene glycol also resulted in a sample with good photocatalytic performance at a low temperature?> 150 ??and sample is of good length of about 800 nm to 1000 nm and a diameter of about 50 nm to 80 nm with a diameter ratio of nanowires,for TiO₂ nanowires/graphene foam composite material preparation to provide a mild reaction conditions.During the preparation of composite materials due to the introduction of graphene foam,on the basis of the best preparation process of TiO₂ nanowires,the reaction temperature,additive temperature and alkali hydrothermal temperature were adjusted to make TiO₂ nanowires/graphene foam composite photocatalytic materials.With the graphene skeleton as the nucleation site,the growth of TiO₂ was affected by the asymmetry force,and the interlaced ultra-thin TiO₂ nanosheets were obtained with the thickness of about 10 nm 20 nm perpendicular to the growth of graphene skeleton.The optimum photocatalytic activity of 1.12 g TiO₂ raw material,50% ethylene glycol and reaction temperature 180 ? was better than that of pure TiO₂ nanowires and TiO₂ raw material in the photocatalytic performance and showed good cycle performance,passing 45 min uv irradiation,photocatalytic efficiency reached 98%.After three photodegradation cycles,the efficiency of photocatalysis remains at this level.