Controllable Fabrication And Photocatalytic Performance Of Metal-Semiconductor Hybrid Nanoarrays

Nowadays,energy for human society mainly comes from the fossil fuel combustion,which causes environmental problems by CO₂ emission.Recently the research of photocatalysts has attached much attention due to the environmental situation.The photocatalysts with nanoarray structures could provide high specific surface area with multiple reflection of incident light,promote the migration of charge carriers and offer more active sites,which have been widely used in photocatalytic and photoelectrochemical reactions.The following two aspects should be improved towards ideal photocatalysts.One is to broaden the light absorption of photocatalysts to a broad spectrum.As the most pioneering and stable photocatalyst,TiO₂ could only absorb ultraviolet light,limiting the use of solar energy.The other aspect is to suppress the charge recombination in semiconductors.In this dissertation,we prepared the inorganic semiconductor nanoarrays as photocatalysts through templating,hydrothermal and electrochemical methods.By the construction of hybrid nanostructure,we optimized the absorption spectra and enhance the activity of the composite photocatalysts.The main research results are summarized as follows:1.BiVO₄ bowl nanoarray structure combined with Au nanoparticles was investigated.Using the colloidal crystal template combined with electron beam evaporation,the BiVO₄ bowl nanoarray was combined with Au nanoparticles.By tuning the size of the PS spheres,the BiVO₄ bowl nanoarrays with different periods could be prepared.The photoelectric properties of BiVO₄ bowl nanoarrays and Au/BiVO₄ bowl nanoarrays with different periods were investigated under visible light illumination.Benefiting from the synergistic effect of the Schottky junction and the surface plasmon,the performance of photocatalytic oxygen evolution was dramatically improved.With the 100-nm periodic Au/BiVO₄ bowl nanoarrays as the photocatalyst,the O₂ yield was 13.6 ?mol h^-1·cm-2,about 4 times that of 100 nm periodic bare BiVO₄ bowl nanoarrays.2.Instead of BiVO₄,N-doped TiO₂ bowl nano array structure combined with Au nanoparticles was investigated.Using the colloidal crystal template combined with electron beam evaporation,the N-doped TiO₂ nanoarray was combined with Au nanoparticles to form Au particles decorated N-TiO₂ bowl nanoarray structure.The photoelectrochemical behavior and photocatalytic water splitting performance with different catalysts under UV,visible and full-spectrum light illumination were studied.The Au particles decorated N-TiO₂ bowl nanoarray structure obtained by annealing in NH3 atmosphere performed the best under the irradiation of ?<550 nm,whose yield of hydrogen was 0.726 mmol g^-1 h^-1.Benefiting from the synergistic effect of the Schottky junction and the energy resonance transfer process,the performance of photocatalytic hydrogen evolution was dramatically improved.3.In order to reduce the cost of catalysts,N-doped TiO₂ nanoarray with Ag-Cu nanoparticles densely supported was investigated.The N-doped anatase TiO₂ nanoplate array and the N-doped rutile TiO₂ nanorod array were prepared by a hydrothermal method and annealing process?NH3 atmosphere?,followed with the photo-deposition and electron-beam evaporation for combination with Ag-Cu nanoparticles.The plasmonic band of Ag nanoparticles sufficiently overlaped with the light absorption of N-doped TiO₂,enabling energy resonance transfer to improve carrier creation and separation.Meanwhile,Cu nanoparticles provided active sites for CO₂ conversion.The photoelectrochemical properties of the composite samples under different light irradiation were studied.Benefiting from the synergistic effect of the Schottky junction and the surface plasmon,the performance of photocatalytic CO₂ reduction was dramatically improved to a rate of 123.7 ?mol·g^-1·h^-1 for CH4 under full-spectrum irradiation.4.The periodic Au net nanoarray/Fe2O₃/CoAl layered double hydroxide?LDH?was investigated.Using the colloidal crystal template-assisted electro-deposition method combined with the hydrothermal method,the three-layer composite structure has been prepared.The optical transmission enhancement for different frequency bands could be tuned by changing the period of Au net array structure,and the photoelectrochemical properties of the composite samples under visible light were studied.By comparing the photoelectrochemical behavior of Fe2O₃,Au net array/Fe2O₃ and Au net array/Fe2O₃ film/CoAl LDH three-layer samples,we believe that the improved performance of the three-layer composite samples in the photoelectrochemical reaction derived from the synergistic effect of the Schottky junction,the plasmon resonance and the cocatalysts effect.