Engineering surface oxygen vacancy of mesoporous CeO_(2) nanosheets assembled microspheres for boosting solar-driven photocatalytic performance

Surface oxygen vacancy defects of mesoporous CeO_(2)nanosheets assembled microspheres(D-CeO_(2))are engineered by polymer precipitation,hydrothermal and surface hydrogenation strategies.The resultant D-CeO_(2)with a main pore diameter of 9.3 nm has a large specific surface area(~102.3 m^(2)/g)and high thermal stability.The mesoporous nanosheets assembled microsphere structure prevents the nanosheets from aggregation,which is beneficial to effective mass transfer and shortens the migration distance of charge carriers.After surface hydrogenation,the photoresponse extends to long wavelength region,combing with the band gap from 2.63 eV reduced to 2.39 eV.Under AM 1.5 G radiation,the photocatalytic degradation rate of tetracycline(TC)can be up to 99.99%,which is three times as high as that of pristine CeO_(2)microspheres.The excellent solar-driven photocatalytic performance can be attributed to the efficient surface oxygen vacancy engineering and the mesoporous nanosheets assembled microsphere structure,which narrows the band gap,shortens the migration distance of carriers,promotes the spatial separation of photogenerated electron-hole pairs and favors mass transfer.The strategy provides new insights for fabricating other high-efficient oxide photocatalysts.

Oxygen vacancy O-terminated surface:The most exposed surface of hexagonal WO3(001)surface

It is known that exposed surface determines material’s performance.WO3 is widely used in gas sensing and its working surface is proposed to control its sensitivity.However,the working surface,or most exposed surface with detailed surface structure remain unclear.In this paper,DFT calculation confirmed that oxygen vacancy O-terminated surface is the most exposed hexagonal WO3(001)surface,judging from competitive adsorption of CO and O2,working surface determination for CO sensing and comparison of oxygen vacancy formation ene rgies on different h-WO3(001)surfaces.It is found that DFT can be a useful alternate for exposed surface determination.Our results provide new perspectives and performance explanations for material research.

Catalytic oxidation of CO over Pt/Fe3O4 catalysts:Tuning O2 activation and CO adsorption

The self-inhibition behavior due to CO poisoning on Pt metal particles strongly impairs the performance of CO oxidation.It is an effective method to use reducible metal oxides for supporting Pt metal particles to avoid self-inhibition and to improve catalytic performance.In this work,we used in situ reductions of chloroplatinic acid on commercial Fe3O4 powder to prepare heterogeneousstructured Pt/Fe3O4 catalysts in the solution of ethylene glycol.The heterogeneous Pt/Fe3O4 catalysts achieved a better catalytic performance of CO oxidation compared with the Fe3O4 powder.The temperatures of 50%and 90%CO conversion were achieved above 260℃and 290℃at Pt/Fe3O4,respectively.However,they are accomplished on Fe3O4 at temperatures higher than 310℃.XRD,XPS,and H2-TPR results confirmed that the metallic Pt atoms have a strong synergistic interaction with the Fe3O4 supports.TGA results and transient DRIFTS results proved that the Pt metal particles facilitate the release of lattice oxygen and the formation of oxygen vacancies on Fe3O4.The combined results of O2-TPD and DRIFTS indicated that the activation step of oxygen molecules at surface oxygen vacancies could potentially be the rate-determining step of the catalytic CO oxidation at Pt/Fe3O4 catalysts.The reaction pathway involves a Pt-assisted Mars-van Krevelen(MvK)mechanism.

A2B2O7 pyrochlore compounds:A category of potential materials for clean energy and environment protection catalysis

A2B2O7 pyrochlore is a kind of important functional materials for different purposes,which has been investigated extensively by crystallographers and material scientists.However,the catalytic chemistry of this type of special compounds has rarely been documented,though a few researchers have tried to synthesize some pyrochlore compounds with different chemical compositions for a variety of green energy production and air pollution control reactions in the history.With the expectation to help catalysis scientists to get better acquaintance with,and gain deeper understanding on this type of compounds as heterogeneous catalysts,the major publications over the past several decades have been screened and reviewed in this paper,based also on our own experience of studying on this type of catalytic materials.The crystalline phase transformations of the compounds with the change of the A and B site cations,the phase change’s influences on the surface and bulk properties,and their subsequent impact on the catalytic performance for different reactions have been summarized.Furthermore,the future work which needs to be performed to perceive in depth this kind of important materials as catalysts has been proposed and suggested.We trust that this short review contains valuable information,which will provide great help for people to get better cognition for A2 B2 O7 pyrochlore compounds,and assist them to develop better catalysts for various reactions.