Controllable Synthesis Of CeO₂-based Hollow Structure Photocatalysts With Catalytic Performance Research

With the rapid development of society and economy,human society is facing numerous problems,the most serious problem which is the energy crisis and environmental pollution.TiO₂,as one of a representative photocatalytic material,has attracted a lot of interests.In recent years,people have done a lot of work on photocatalytic materials.However,those photocatalysts like TiO₂ has many disadvantages,for example: wide band gap,ultraviolet response only,low quantum yield.These problems greatly restrict the application of photocatalysts.Cerium dioxide?CeO₂?,as one of the most important semiconductor materials,is very useful in several key applications,including adsorbents,catalysts,fuel cells,gas sensors,and luminescence.With a decrease in particle size,there usually are high densities of interfaces in nanocrystalline leading to markedly increased levels of nonstoichiometry and electronic carrier generation.Therefore,nanostructured CeO₂ has attracted much attention due to improvements in the redox properties,transport properties and surface to volume ratio with respect to the bulk mate-rials.A vast number of papers related to the topic of nanostructured ceria and their photocatalytic applications have been published in recent years.In the present work,we report the preparation of novel CeO₂-based nanostructures and the study of photocatalytic performances.The key factors to improve CeO₂ samples' photocatalytic activity have also been explored.The details are summarized briefly as follows:?1?Various morphologis of Cu2 O nanocrystals templates,including cubic,polyhedral,octahedral and spherical nanocrystals,have been fabricated through an ordinary solution reduction method.The physical properties of the Cu2 O nanocrystals samples were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?.?2?The novel CeO₂ hollow structures with uniform cubic,polyhedral and sphere shapes were successfully synthesized by template-engaged coordinating etching of shape-controlled Cu2 O crystals.The obtained samples were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microcopy?TEM?,high resolution of transmission electron microcopy?HRTEM?,X-ray photoelectron spectroscopy?XPS?,electron spin resonance?ESR?and photoluminescence spectroscopy?PL?.The photocatalytic oxygen evolution via water oxidation was investigated for CeO₂ hollow structures with varied shapes under visible light irradiation.The photocatalytic results indicate that polyhedral CeO₂ nanocages show the highest photocatalytic activity,which can be attributed to the unique properties of the polyhedral CeO₂ nanocages,including efficient light refection through the inner shells,more active sites for enhancing separation efficiency of charge carriers.?3?CoO_x/CeO₂ nanocomposites with different CoO_x contents have been synthesized by a liquid impregnation method.CoO_x nanoparticles,as co-catalysts,were loaded on the surface of octahedral CeO₂ nanocages.To explore the influences of co-catalyst on the photocatalytic performance,XRD,SEM,TEM and XPS,UV-vis and SPV tests were used to characterize the physical and photophysical properties of the composite catalyst.The photocatalytic oxygen evolution via water oxidation was investigated for CoO_x/CeO₂ nanocomposites under visible light irradiation.A possible catalytic mechanism for CoO_x/CeO₂ nanocomposites is proposed.In summary,novel hollow CeO₂-based nanomaterials photocatalysts have been constructed to study and improve their photocatalytic performances.And it is found that construction of heterostructured semiconductor is a promising way to enhance its visible light harvesting ability,the separation rate of electon-holes and photocatalytic performance.It is expected that this study could provide helpful results for designing and exploration of novel hollow structures with tunable photocatalytic performance.