The Preparation And Investigation Of Photoelectrocatalytic Methanol/ethanol Oxidation For ?-Fe₂O₃-based Nanocomposite Materials

Semiconductor photoelectrocatalytic alcohols oxidation is a green and sustainable technology that converts solar energy into chemical energy.?-Fe₂O₃ is considered to be one of the most promising photocatalysts for photoelectrocatalytic alcohols oxidation because of its suitable band structure?around 2.1 eV?,low cost,abundant storage,and is environmentally friendly.Meanwhile,?-Fe₂O₃ not only is the most stable phase in iron oxide,but also it can work as the raw material to synthesis of?-Fe₂O₃ and Fe₃O₄.However,there are still many disadvantages of?-Fe₂O₃ were reported in many literatures,such as slow oxidation kinetics and low Faraday efficiency.The poor conductivity of?-Fe₂O₃ and the short holes diffusion length?2-4 nm?of?-Fe₂O₃ are the main reason,which limit its further large-scale application.Therefore,to modify?-Fe₂O₃ reasonably,such as the reduction of photogenerated electron-hole pair recombination,the increase of photoresponse current density,and the effective improvement of its photocatalytic activity,those strategies had attracted the majority of researchers.In this thesis,?-Fe₂O₃-based composite nanotube arrays have high photoresponse current,good performance and excellent stability,which were modified by suitable improvement strategies,such as Z-type electron transmission paths loading precious metals,compounding other semiconductors,doping transition metals,and the photocatalytic oxidation of alcohols with?-Fe₂O₃ was also studied.The main means are following:?1?ZnO/?-Fe₂O₃/Au nanotube arrays were prepared using ZnO nanorod arrays as templates by electrochemical bath deposition,sacrificial template accelerated hydrolysis and simple reduction reaction.Hydrolysis of Fe³⁺accelerated the dissolution of ZnO nanorod arrays templates.?-Fe₂O₃ is combined with ZnO,which leads to red shift of the absorption wavelength?the shift of absorption ranges from ultraviolet light to visible light?.As a photosensitizer,the Au nanoparticles can absorb the light energy,and the photoexcited hot electronswere injected into the conduction band of the?-Fe₂O₃ due to the surface plasmon resonance effect?SPR?,which leads to significant enhancement of the carrier density of the composite semiconductor and inhibition of photogenerated electron-hole pair recombination.And the structure of ZnO/?-Fe₂O₃/Au nanotube arrays are hollow,which can further increase the specific surface area,expose more active sites,provide a channel for rapid transfer of photogenerated electrons,and promote the effective separation and transmission of photogenerated electron-hole pairs,further reduce the recombination of photogenerated electron-hole pairs.?2?ZnO/?-Fe₂O₃/g-C₃N₄ nanotube arrays were successfully prepared by electrochemical bath deposition,sacrificial template accelerated hydrolysis and thermal condensation polymerization.As a semiconductor material,g-C₃N₄ has some advantages:such as suitable band structure,wide source of precursors,no metal in composition,low manufacturing cost.At the same time,it can match with?-Fe₂O₃,so g-C₃N₄ is one of the modern popular materials,recognized by many researchers.Meanwhile,g-C₃N₄ has large surface area and abundant active sites,which can form strong electron coupling with photocatalyst.Based on its two-dimensional structure,it can promote the photo-excitation charge transfer in the interface and make effective use of visible light.?3?High-performance ZnO/Mo-Fe₂O₃/MoO₃ nanotube arrays were successfully prepared by simple electrochemical bath deposition and sacrificial template accelerated hydrolysis.The composite catalyst ZnO/Mo-Fe₂O₃/MoO₃ nanotube array has high photoresponse current density,low electrochemical impedance spectroscopy,and high alcohol Faraday efficiency.