Study On The Preparation And Property Of CeO₂ Based Photocatalyst Driven By Visible Light

Photocatalytic hydrogen production from water splitting is a possible ways to solve the environment and energy issues for sustainable development,the design and synthesis highly efficient and stable photocatalysts is the key of photocatalytic hydrogen production technology.CeO2 has some properties such as stable chemical property,preferably redox potential,non-toxic and easy modification,has been widely used for photocatalysis.However,CeO2 exhibits some defects,such as broad band gap which absorbs light in the UV and slightly in the visible light region,and the low quantum efficiency further limits its application.Thus,the goal of thesis is develop highly efficient and stable visible-light-driven CeO2 based composite photocatalyst.Through the narrow bandgap material CdS and noble metals Pt and combinations modified CeO2 respectively.Study on photocatalytic hydrogen evolution activity of Ce02 based photocatalyst driven by visible light,The relationship on structure and photocatalytic H2 production activity were investigated.The main results and conclusions obtained from the present research are as follows:1.CdS nanoparticles(NPs)/CeO2 nanorods(NRs)composites with effective contacts were synthesized through a two-step hydrothermal method.CdS/CeO2 composite possess high-efficiency visible-light-driven photocatalytic activity and high photostability,the CdS NPs/CeO2 NRs composite with a proper mole ratio(1:1)was responsible for the highest H2-production rate of 8.4 mmol h-1g-1 under visible-light irradiation(?>420 nm),which suggests a high AQY up to 11.2%.The results of structure characterization show that diameter of 10-20 nm cubic structure of CdS nanoparticles is uniformly dispersed in the 10-20 nm diameter,100-500 nm long cubic structure of CeO2 nanorods,with effective contacts.The UV-vis diffuse reflectance spectra of CdS/CeO2 indicates these composites have a better light-harvesting ability in comparison with CeO2 NRs and can absorb the visible light,The superior photocatalytic H2 evolution properties were attributed to the transfer of visible-excited electrons of CdS NPs to CeO2 NRs,which could effectively extend the light absorption range of wide-band gap CeO2 NRs,and the more effective charge separation of electron-hole pairs and the faster charges transfer through interfacial,which is beneficial for its photocatalytic activity.2.CdS-Pt@CeO2 nanostructure was synthesis by a two-step precipitation method,Pt@Ce02 fabricated by the redox reaction just simply happened between Ce(NO3)3 and H2PtCl6 in an alkaline aqueous solution,then CdS nanoparticles grown on Pt@CeO2 by precipitation method.the nanostructure exhibit a dramatically high photocatalytic H2-generation rate of 20.09 mmol h-1g-1 under visible light(?>420 nm)irradiation,which suggests a high AQY up to 26.79%.The results of structure characterization show that diameter of 5-8 nm Pt nanoparticles were all covered in composite,The results on surface area,fluorescence and photoelectric properties of CdS-Pt@CeO2 show large specific surface area and the interaction between Pt NPs,CdS and CeO2,contribute to the enhanced separation and transfer of photoelectrons and holes,and therefore improving its electrochemical properties and H2 evolution rate.We believe that our work demonstrates a promising way for the rational design of semiconductor hybrid photocatalysts that can achieve a high photocatalytic efficiency for use in solar fuels production.