Photocatalytic Performance And Mechanism Of Oxide Heterojunction Based On Atomic Layer Deposition

Atomic layer deposition(ALD)is known for its controlled growth technique of film,which can precisely control the growth of particles at the nanoscale or even at the atomic level.This makes it widely used to solve the problems caused by the nanoscale of materials and devices.It can grow uniform dense films on various shapes of substrates.Nowadays,the research of island structure highly dispersed on the substrate catalyst prepared by ALD method is still in the initial stage.Many noble metal supported photocatalysts have used this method to increase the active sites of the catalyst in order to enhance the photocatalytic.In this work,three photocatalysts were prepared by this method,named as Bi2O3/TiO2 photocatalyst,MnO2/TiO2 photocatalyst and MnO2/Bi2O3/TiO2 photocatalyst respectively.The lattice structure,surface morphology and chemical composition of the samples were analyzed by X-ray diffraction(XRD)and scanning electron microscope(SEM).The photocatalytic activity of the samples was measured by the photocatalytic of MB.Photoluminescence spectroscopy(PL)was used to verify the separation of photogenerated charge carriers.Several experiments were carried out to testify the stability of the photocatalyst.The mechanisms of these three heterojunctions were proposed to analyze the transfer of photogenerated charge carriers.The results showed that the MnO2 and Bi2O3 nanoparticles prepared by ALD method could be uniformly dispersed on the surface of TiO2 photocatalyst,and the number of formed heterojunctions was varied due to the different particle components and sizes,resulting in various photocatalytic performance.The photocatalytic performance of the three heterogeneous photocatalysts is obviously better than that of TiO2 photocatalyst.In the Bi2O3/TiO2 photocatalyst,Bi2O3 exists in the form of nanoparticles and large clusters.Due to the high composite rate of Bi2O3 nanoparticles in large clusters,the photogenerated charge carriers cannot be separated effectively.Therefore,due to the narrow band gap of MnO2 can effectively expand the visible absorption range of heterojunction.The Type-I photogenerated carrier transfer mechanism formed by N-N heterojunction can effectively separate photogenerated electron-hole pairs.The Bi2O3/TiO2 photocatalys is not as high photocatalytic efficiency as that of MnO2/TiO2 photocatalyst.What's more,the N-P-N heterojunction formed by the ternary heterocatalyst MnO2/Bi2O3/TiO2 has higher photocatalytic than the binary heterojunction,which the photocatalytic mechanism of ternary photocatalyst is generated by the synergistic effect of Bi2O3/TiO2 heterojunction,MnO2/TiO2 heterojunction and MnO2/Bi2O3/TiO2 heterojunction.