Application Of TiO₂ Based Composite Semiconductor In Photocatalytic Fuel Cell

With the development of heavy industry,non-renewable energy sources such as oil and coal have been exhausted in recent years.The rapid development of industry not only brings convenience to people,but also brings pollution to the environment,such as textile dyes that are difficult to degrade and some toxic and harmful heavy metal ions.Photocatalytic and photoelectric catalysis technology can easily decompose the organic macromolecular material,or even completely degradation for security environmental protection inorganic small molecules,especially for stable chemical properties,difficult in the air since the degradation of textile dyes.For its inexhaustible,flexible,low cost,easy to get,etc,solar energy will be the ideal choice.Compared with the first-and second-generation solar cells,dye-sensitized solar cells（DSSCs）have been widely paid attention because of their low cost and good performance.Recently,as a new type of cell that can both degrade pollutants and generate electricity,which can be comparable to the degradation efficiency of pure photocatalytic reaction,photocatalytic fuel cell（PFC）is being studied by more and more scientists.In this paper,the zero-dimensional nano-TiO₂ material with high specific surface area is simply and effieciently prepared by a hydrothermal post-treatment to the as-prepared titanium dioxide（TiO₂）,and then applied in the photocatalytic reaction.In addition,one-dimensional nitrogen-doped TiO₂ nanorod arrays（N-TNAs）are synthesized by doping and immobilization method,and then applied in dye-sensitized solar cells.Finally,the composite nano-particle Ag@Fe₂O₃ with Ag as the core and Fe₂O₃ as the shell was obtained by condensation reflux method.The Ag@Fe₂O₃composite material was used as the cathode to assemble PFC with TiO₂ nanocrystalline as the anode,which can degrade organic dyes and generate electricity.The main work is as follows:（1）Nano-TiO₂ particles with uniform particle size were prepared by mild hydrolyzation-hydrothermal method,and titanium（Ti（i-Pro）₄）was selected as the titanium source.On this basis,excellent post-treated TiO₂ photocatalyst with excellent catalytic performance was obtained by simple hydrothermal post-treatment method,and the crystal form of TiO₂did not change after hydrothermal treatment.It is characterized by large surface area,small particle size,porous and hydrophilic surface.In this experiment,parameters such as temperature,time,solvent,calcination method and type of TiO₂ were optimized.When the aggregated nanoparticles were treated under high temperature and pressure,the crystal structure of TiO₂ was seriously damaged and then reconstructed.With the increase of specific surface area,average pore size,total pore volume and the generation of oxygen vacancy,the dispersion of particles is greatly improved and the typical mesoporous structure is formed.These changes can make the dyes better adsorbed on the photocatalyst,thus speeding up the degradation.For example,the post-processing TiO₂ dye degradation kinetics constants(0.085 min^-1)than the untreated TiO₂(0.0085 min^-1)increased 10 times Through electrochemical experiments show that TiO₂ hydrothermal post-processing can accelerate the reduction reaction of O₂,improve photoinduced charge transfer process By free radical quenching experiments show that reprocessing or unprocessed TiO₂ are given priority to with super oxygen free radical(O₂^-·),but the post-processing significantly promoted the generation of hydroxyl radical（·OH）,which makes the post-processing of TiO₂ photocatalysis performance has improved significantly.（2）A simple and efficient hydrothermal method was used to synthesize N-TNAs on Sn O₂ conductive glass（FTO）doped with fluorine using Ti（OBu）₄and ammonium chloride（NH₄Cl）as sources of titanium and nitrogen,respectively.Nitrogen doping is often used to expand the response range of wide-band gap semiconductors to improve their photoelectric properties.This study is the first to demonstrate that NH₄⁺has a unique morphological regulation effect on one-dimensional TiO₂ nanorod arrays（TNAs）,but the nitrogen doping effect has rarely been detected.The addition of NH₄Cl greatly promoted the growth of TNAs,especially the radial growth,but a small amount of nitrogen in NH₄⁺could enter the modified TNAs and become N-TNAs.In addition,compared with TNAs,the band energy of N-TNAs almost did not change,indicating that the doping of trace nitrogen did not affect the response to radiation.When the dye-sensitized solar cells were assembled with N-TNAs as the photoanode,the optimum photoelectric conversion efficiency（3.16%）was almost double that of the photoelectric conversion efficiency（1.62%）prepared with TNAs.It is noteworthy that the improvement of efficiency was mainly due to the photoinduced current,rather than the voltage.Secondly,the change of conversion efficiency is related to the length of the nanorods.In conclusion,the improvement of the photoelectric performance of the nanorods is due to the directional growth of the nanorods,while the directional growth results in the addition of NH₄⁺as an effective structure regulator.（3）The Ag@Fe₂O₃ is synthesized by a condensation reflux method with Ag as the nuclear and Fe₂O₃ as the shell,respectively.Through a series of characterization testing（XRD,XPS,SEM,etc.）,the existence of Ag@Fe₂O₃ is proved.A new type of dual-chamber photocatalytic dye fuel cells with composited functions is designed and optimized,using TiO₂as the anode and Ag@Fe₂O₃as cathode.The degradation of dye in anode and the reduction of Cr（Ⅵ）in cathode make the oxidation and reduction reactions occur in different chambers,resulting in the purification of various pollutants.The effects of different cathode materials,the concentration of potassium dichromate,the change of p H and the concentration of H₂O₂ are discussed.Adding H₂O₂ can accelerated anodic reaction by increasing the content of oxide,so as to improve the degradation in anode chamber and the reduction in cathode chamber.