Preparation And Application Of Metal-Cerium Dioxide Heterojunction

As a common rare earth compound,Ceria?CeO₂?is always present as a pale yellow or white powder throughout nature.Due to its unique electronic structure,CeO₂ shows excellent redox performance and excellent oxygen storage capacity?OSC?.Therefore it is known as a star material in the field of solar cells and catalysis.To date,CeO₂ has reached market and large-scale production in the application of three-way catalysts?TWCs?.At the moment,the research of CeO₂ has also attracted widespread attention in the field of fuel cells.What's worse,due to the reversible transfer of electrons between Ce?IV?and Ce?III?and excellent OSC in the CeO₂,it has been the focus in many application fields,such as reforming reactions,water gas shift reactions?WGSR?,CO preferential oxidation,organic reactions,oxidation of volatile organic compounds?VOCs?,and photocatalytic reactions.Undoubtedly,because of the small size and large specific surface area,the surface activity of nano-CeO₂ has greatly advanced.However,considering these features,it's well known that CeO₂ nanostructures tend to agglomerate in catalytic reactions.Ceria can be surface-modified to solve the problem.In this way,the catalytic performance of CeO₂ nanomaterials is improved by reducing the surface tension.At the same time,the scope of application of CeO₂ nanomaterials can be broadened in this way.In the work,we synthesized metal-ceria heterojunction materials by interfacial chemical reaction method and impregnation reduction method.Therefore,we explored the application of benzyl alcohol oxidative esterification,photodegradation and formaldehyde hydrogen production at room temperature.CeO₂ nanorods are prepared by hydrothermal method.Moreover,Au-CeO₂ nanostructures are synthesized by interfacial chemical reaction method and impregnation reduction method.Immediately,in order to research the catalytic activity and stability of Au-CeO₂,they have been applied to the oxidative esterification of benzyl alcohol.The results showed that the activity and stability of Au@CeO₂ heterojunction prepared by interfacial chemical method were higher than that of Au-CeO₂ prepared by impregnation reduction method.Especially,the yield of 3wt%Au@CeO₂ catalyzed oxidative esterification of benzyl alcohol was 56.1%.Ag NPs were supported on CeO₂ support?Ag-CeO₂?by interfacial chemical reaction method and impregnation reduction method.Then,as light source by UV or Xenon lamp,malachite green?MG?or carbamazepine?CBZ?pollutants have been photodegraded by Ag-CeO₂.The results show that the photodegradation efficiency is profoundly influenced by the facters,which are target pollutants and catalyst,Ag loading in Ag-CeO₂,pH and oxidant.The mechanism of photodegradation was explored through free radical capture experiments.The results show that the active species,which promote photodegradation of MG or CBZ,are both photogenerated holes?h⁺?and hydroxyl radicals?·OH?.Pd-CeO₂ heterojunction materials which were synthesized by interfacial chemical reaction method and impregnation reduction method catalyzed hydrogen production from formaldehyde at room temperature.It turns out that the factors affecting the rate of hydrogen production are these conditions,which are the initial formaldehyde concentration,initial NaOH concentration,Pd loading amount in Pd-CeO₂ and temperature.The 2.1 wt%Pd@CeO₂,which prepared by the interfacial chemistry method,had the best catalytic activity and the best average hydrogen production rate was 156.0 mL·min^-1·g^-1_cat..In summary,the metal-cerium dioxide heterojunction materials show good catalytic activity and stability in the fields of oxidative esterification of alcohols,photodegradation and formaldehyde hydrogen production.The preparation process of CeO₂-based heterojunction is simple and has broad application prospects in the field of catalysis.