Study On The Conductive Channel Introduced By Solid Phase Reaction Method To Enhance The Degradation Of Organic Pollutants Coupled With Hydrogen Production Of Z-scheme Photocatalyst

With the rapid development of industrialization and urbanization,the problems of energy shortage and environmental pollution have become two important factors restricting the sustainable development of economy and society.In recent years,photocatalysis,as an efficient,economical and environmentally friendly technology,has been widely used by some researchers to catalyze organic pollutants degradation or hydrogen production.It is expected to become one of the most potential methods to solve the above two problems.In recent years,Z-scheme photocatalytic system has been widely studied by scholars due to its strong redox ability and wide light response range.However,in order to construct a more highly efficient Z-scheme photocatalytic system,it is necessary to introduce a conductive channel to enhance the separation efficiency of photo-generated electron and hole pairs.Previously,based on the Z-scheme photocatalytic system,some precious metals,carbon nanotubes and graphene were usually added as conductive channels to enhance the separation efficiency of photo-generated electron and hole pairs.Although they can promote the transfer of photo-generated electrons to some extent,some shortcomings still exist.For example,the traditional conductive channels require to be additionally introduced to the photocatalytic system,but it is very difficult in fact.Moreover,even if the traditional conductive channels are introduced in form,it is still not conducive to the transfer of electrons.The reason is that,with the extra introduction of the traditional conductive channel,two new interfaces are formed between the conductive channel and the two semiconductor photocatalysts.It is very difficult for the transfer of electrons to pass through these interfaces continuously.In addition,the contact between particles is usually point-to-point,which is still a bottleneck for photo-generated electrons to pass through such conductive channel.To solve the above problems,a narrow band gap semiconductor was skillfully introduced into two semiconductor photocatalysts by solid phase reaction method.The narrow band semiconductor can be used as conductive channels to accelerate the transfer of photo-generated electrons,effectively improving the separation efficiency of photo-generated electron and hole pairs.Furthermore,the catalytic performance of Z-scheme photocatalytic system can be enhanced.In this work,we used the solid phase reaction method to construct a series of visible light responded photocatalysts.The crystal structure,surface morphology,microstructure,chemical composition,functional group and the optical absorption properties of prepared samples were characterized by X-ray diffraction?XRD?,scanning electron microscope?SEM?,transmission electron microscopy?TEM?,energy dispersive X-ray spectroscopy?EDX?,X-ray photoelectron spectroscopy?XPS?and UV-vis diffuse reflection spectroscopy?UV-DRS?.The separation efficiency of photo-generated electron and hole pairs of the prepared samples was tested by photoluminescence spectroscopy?PL?,photocurrent response?TPR?and electrochemical impedance?EIS?.In the first part,we studied the effects of treatment temperature and treatment time of CeO2/V2O5 composite on catalytic degradation of organic pollutants with simultaneous hydrogen production caused by Z-scheme CeO₂/CeVO₄/V₂O₅ photocatalyst.The experimental results showed that,when the CeO₂/V₂O₅ composite was calcined at 550°C for 3.0 h,Z-scheme CeO₂/CeVO₄/V₂O₅?550-3?photocatalyst possessed the highest catalytic activity.This is because when the treatment temperature is 550°C and the treatment time is 3.0 h,a moderate amount of CeVO₄ nanoparticles can be formed between CeO₂ and V₂O₅.The formation of Ce VO4 nanoparticles can be used as effective conductive channels to promote the transfer of photo-generated electrons,effectively enhancing the separation efficiency of photo-generated electron and hole pairs.In the second part of the study,we studied the effects of treatment temperature and treatment time of CoO?111?/Fe2O3 composite on catalytic degradation of organic pollutants with simultaneous hydrogen production caused by Z-scheme CoO?111?/CoFe2O4/Fe2O3photocatalyst.The experimental results showed that,when CoO?111?/Fe2O3composite was calcined at 450°C for 2.0 h,Z-scheme CoO?111?/CoFe2O4/Fe2O3?450-2?photocatalyst exhibited the highest catalytic activity.There are two reasons as follows:?i?when the treatment temperature is 450°C and the treatment time is 2.0 h,a moderate amount of CoFe2O4 nanoparticles are formed between CoO?111?and Fe2O3.The formation of CoFe2O4 nanoparticles can be used as effective conductive channels to promote the transfer of photo-generated electrons,enhancing the separation efficiency of photo-generated electron and hole pairs.?ii?when the CoO with high activity?111?surface is excited,the photo-generated electrons can quickly gather on the high activity?111?surface,thus forming an electric field in the CoO,effectively enhancing the separation efficiency of photo-generated electron and hole pairs.This study will afford a simple and novel method to design and develop highly efficient Z-scheme photocatalysts.