Investigation On Preparation Of Photocatalytic System NaTaO₃ And NiGa₂O₄-BiVO₄ Degradation Of Organic Pollutants With Simultaneous Hydrogen Evolution Under Visible Light Irradiation

Semiconductor photocatalytic technology has been wide application prospects for degradation of organic pollutant and water splitting.The pollutants can be considered as an available resource,through using an appropriate photocatalyst that degradation of pollutants and hydrogen production can be achieved simultaneously.This idea not only conserves resources but also can achieve the dual purposes of environmental remediation and energy crisis.We choose the wide band gap semiconductor photocatalyst with strong redox ability to efficiently realize photocatalytic degradation of refractory pollutant with simultaneous hydrogen evolution.However,this kind of photocatalyst has defects in application,firstly,the wide band gap only can absorb the high-energy ultraviolet light.Unfortunately,the ultraviolet light part accounts for 5.0 % in the sunlight,which inevitably makes the solar energy utilization rate of photocatalyst extremely low.Secondly,the recombination rate of photocatalyst is very high,influenceing the efficiency of photocatalytic reaction.Therefore,in order to solve the aforementioned question,we choose to use up-conversion luminescence agent and co-catalysts.Some up-conversion luminescence agents can convert the low-energy visible light into high-energy ultraviolet light,which satisfy the requirement of wide gap photocatalyst for ultraviolet light.The co-catalyst can transfer electrons or holes quickly to prevent them recombination.Based on the above opinions,we design new photocatalytic system that combineing wide band gap photocatalyst with up-conversion luminescence agent and loading the co-catalyst on the photocatalyst can better realize degradation pollutant with simultaneous hydrogen evolution.In the first chapter,a new visible-light-sensitive photocatalyst,Er³⁺:Y₃Al₅O₁₂/MoS₂-NaTaO₃-PdS,was prepared by hydrothermal,liquid boiling and deposition methods.The prepared photocatalysts were all characterized by X-ray diffractometer?XRD?,energy dispersive X-ray spectroscopy?EDX?,scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.Thephotocatalytic activity of prepared photocatalysts was evaluated via photocatalytic degradation of amaranth as refractory pollutant with simultaneous hydrogen evolution under visible-light irradiation.Moreover,the effects of visible-light irradiation time,molar ratio of Er³⁺:Y₃Al₅O₁₂ and NaTaO₃,co-catalyst and resue times on the photocatalytic capability of Er³⁺:Y₃Al₅O₁₂/MoS₂-NaTaO₃-PdS were studied.Finally,The visible-light photocatalytic degradation mechanism of amaranth with simultaneous hydrogen evolution was also proposed.In the second chapter,a new visible-light-induced Z-scheme photocatalytic system,Er³⁺:Y₃Al₅O₁₂/?MoS₂/NiGa₂O₄?-?BiVO₄/PdS?,was designed using hydrothermal and mixed-calcination methods.And the prepared samples were characterized by X-ray diffractometer?XRD?,energy dispersive X-ray spectroscopy?EDX?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?,Fourier-transform infrared?FTIR?and UV-vis absorption spectra.The photocatalytic activity of these photocatalysts were evaluated towards Orange G degradation with simultaneous hydrogen evolution under visible-light irradiation.the effects of visible-light irradiation time,molar ratio of Ni Ga2O4 and BiVO₄ and resue times on the photocatalytic capability of Er³⁺:Y₃Al₅O₁₂/?MoS₂/NiGa₂O₄?-?BiVO₄/PdS?were studied.In addition,the possible Z-scheme mechanism of Er³⁺:Y₃Al₅O₁₂/?MoS₂/NiGa₂O₄?-?BiVO₄/PdS?was also proposed,and further evidenced by photoluminescence?PL?.Through the research,we found that compositing with the up-conversion luminescent material could improve the utilization efficiency of sunlight.Used co-catalysts suppress the recombination of photogenerated electron?e-?-hole?h+?pairs to enhance the photocatalytic activity.The formation of Z-system can make the photocatalytic system with strong redox ability.This study provides a new way to use solar energy for photocatalytic degradation of pollutants simultaneously.