Construction Of Several Dual Z-scheme Photocatalytic Systems And Studies On Photocatalytic Degradation Of Organic Contaminants With Simultaneous Hydrogen Production

Due to the serious energy crisis and environmental pollution,it is urgent to develop a kind of energy with renewability and harmless to the environment.Recently,semiconductor photocatalysts have attracted the attention of many researchers,since they likely offer the“green”routes for completely degrading pollutants,producing hydrogen?H₂?out of water and converting carbon dioxide into hydrocarbons.Particularly,the photocatalytic degradation with simultaneous hydrogen production displays a broad application prospect.It can not only produce hydrogen to mitigate the energy crisis,but also solve the problem of environmental pollution.In order to achieve the efficiently photocatalytic degradation and hydrogen production at the same time,some wide band-gap semiconductor photocatalysts with strong redox capacity should be selected.However,such photocatalysts have a defect in factual application.That is,they can only absorb ultraviolet-light due to the wide band-gaps.Nevertheless,in sunlight,the ultraviolet-light accounts for only 5.0%,which results in a low utilization rate of sunlight.Therefore,some researchers have begun to pay attention to the binary photocatalysts.Among binary photocatalysts,Z-scheme photocatalyst has a better application prospect.In a Z-scheme photocatalytic system,the photo-induced electrons with strong reduction ability on the conduction band and holes with strong oxidation ability on the valence band are preserved,respectively.It forebodes that a Z-scheme photocatalytic system has both strong oxidation and reduction abilities to perform photocatalytic degradation of organic pollutants with simultaneous hydrogen production reactions.However,the relatively high recombination rate of e^-and h⁺in respective photocatalysts is still an intractable problem.These problems can be effectively solved by improving the Z-scheme photocatalytic system.In order to suppress the recombination of photo-generated electrons and holes in the photocatalytic system and maintain strong redox ability,this study adds a heterojunction photocatalytic system to provide more routes for photo-generated electrons and holes to transport and reduce their transmission resistance.This study also improved the Z-scheme photocatalytic system by forming a dual Z-scheme photocatalytic system.Forming a larger oxidation surface to further enhance the photocatalytic ability,and then improve the photocatalytic activity.In the first part of the study,a ternary annual 2Z-scheme+1 heterojunction CuO/WO₃/CdS/???2Z+1H?CuO/WO₃/CdS/?photocatalyst was prepared by hydrothermal and isoelectric point methods.XRD,SEM,TEM,UV-vis,EDX,XPS and related electrochemical tests were used to characterize the prepared samples.The photocatalytic activity of the composite photocatalyst was evaluated by degrading methylene blue with simultaneous hydrogen producing under the visible light irradiation.The effects of light irradiation time and reuse times on the efficiency of photocatalytic degradation of methylene blue and the efficiency of photocatalytic hydrogen production were analyzed.In addition,the photocatalytic mechanism of??2Z+1H?CuO/WO₃/CdS/photocatalyst was proposed.In the second part of the study,a dual Z-scheme Ni O/Ni Co₂O₄/Co₃O₄ photocatalyst was synthesized by the synchronous conversion method.XRD,SEM,UV-vis,EDX,XPS and related electrochemical tests were used to characterize the prepared samples.The effects of sunlight irradiation time,calcination temperature,ratio of materials,calcination time and reuse times on the photocatalytic degradation and hydrogen production efficiency were systematically analyzed.In addition,the photocatalytic mechanism of the dual Z-scheme NiO/NiCo₂O₄/Co₃O₄ photocatalyst was proposed.