Co3O4/SiO2 catalysts for CO oxidation were prepared by conventional incipient wetness impregnation followed by calcination at various temperatures. Their structures were char- acterized with X-ray diffraction （XRD）,...Co3O4/SiO2 catalysts for CO oxidation were prepared by conventional incipient wetness impregnation followed by calcination at various temperatures. Their structures were char- acterized with X-ray diffraction （XRD）, laser Raman spectroscopy, X-ray photoelectron spectroscopy （XPS）, temperature-programmed reduction （TPR） and X-ray absorption fine structure （XAFS） spectroscopy. Both XRD and Raman spectroscopy only detect the existence of Co3O4 crystallites in all catalysts. However, XPS results indicate that excess Co2＋ ions are present on the surface of Co3O4 in Co3O4（200）/Si02 as compared with bulk Co3O4. Meanwhile, TPR results suggest the presence of surface oxygen vacancies on Co3O4 in Co3O4（200）/SiO2, and XAFS results demonstrate that Co3O4 in Co3O4（200）/SIO2 contains excess Co2＋. Increasing calcination temperature results in oxidation of excess Co2＋ and the decrease of the concentration of surface oxygen vacancies, consequently the for- mation of stoichiometric Co3O4 on supported catalysts. Among all Co3O4/SiO2 catalysts, Co3O4（200）/SiO2 exhibits the best catalytic performance towards CO oxidation, demonstrating that excess Co2＋ and surface oxygen vacancies can enhance the catalytic activity of Co3O4 towards CO oxidation. These results nicely demonstrate the effect of calcination temperature on the structure and catalytic performance towards CO oxidation of silicasupported Co3O4 catalysts and highlight the important role of surface oxygen vacancies on Co3O4.展开更多
Inefficient charge separation and limited light absorption are two critical issues associated with high‐efficiency photocatalytic H2production using TiO2.Surface defects within a certain concentration range in photoc...Inefficient charge separation and limited light absorption are two critical issues associated with high‐efficiency photocatalytic H2production using TiO2.Surface defects within a certain concentration range in photocatalyst materials are beneficial for photocatalytic activity.In this study,surface defects(oxygen vacancies and metal cation replacement defects)were induced with a facile and effective approach by surface doping with low‐cost transition metals(Co,Ni,Cu,and Mn)on ultrafine TiO2.The obtained surface‐defective TiO2exhibited a3–4‐fold improved activity compared to that of the original ultrafine TiO2.In addition,a H2production rate of3.4μmol/h was obtained using visible light(λ>420nm)irradiation.The apparent quantum yield(AQY)at365nm reached36.9%over TiO2‐Cu,significantly more than the commercial P25TiO2.The enhancement of photocatalytic H2production activity can be attributed to improved rapid charge separation efficiency andexpanded light absorption window.This hydrothermal treatment with transition metal was proven to be a very facile and effective method for obtaining surface defects.展开更多
TiO2 nanoparticles have been synthesized by using a TiO2@NaCl core-shell structure as the precursor. The surface defects were well preserved by the NaCl shell, and therefore high oxygen adsorption capacity was observe...TiO2 nanoparticles have been synthesized by using a TiO2@NaCl core-shell structure as the precursor. The surface defects were well preserved by the NaCl shell, and therefore high oxygen adsorption capacity was observed. After the NaC1 shell was removed, the resulting pure TiO2 nanoparticles were of anatase phase and uniform size of around 20-24 nm. The presence of an abundance of surface defects contributes to the high photocatalytic activity of the synthesized materials, and the TiO： mate- rials obtained from the TiO2@NaCl precursor can be used as efficient photocatalysts for degradation of rhodamine B under UV light irradiation.展开更多
文摘Co3O4/SiO2 catalysts for CO oxidation were prepared by conventional incipient wetness impregnation followed by calcination at various temperatures. Their structures were char- acterized with X-ray diffraction （XRD）, laser Raman spectroscopy, X-ray photoelectron spectroscopy （XPS）, temperature-programmed reduction （TPR） and X-ray absorption fine structure （XAFS） spectroscopy. Both XRD and Raman spectroscopy only detect the existence of Co3O4 crystallites in all catalysts. However, XPS results indicate that excess Co2＋ ions are present on the surface of Co3O4 in Co3O4（200）/Si02 as compared with bulk Co3O4. Meanwhile, TPR results suggest the presence of surface oxygen vacancies on Co3O4 in Co3O4（200）/SiO2, and XAFS results demonstrate that Co3O4 in Co3O4（200）/SIO2 contains excess Co2＋. Increasing calcination temperature results in oxidation of excess Co2＋ and the decrease of the concentration of surface oxygen vacancies, consequently the for- mation of stoichiometric Co3O4 on supported catalysts. Among all Co3O4/SiO2 catalysts, Co3O4（200）/SiO2 exhibits the best catalytic performance towards CO oxidation, demonstrating that excess Co2＋ and surface oxygen vacancies can enhance the catalytic activity of Co3O4 towards CO oxidation. These results nicely demonstrate the effect of calcination temperature on the structure and catalytic performance towards CO oxidation of silicasupported Co3O4 catalysts and highlight the important role of surface oxygen vacancies on Co3O4.
基金supported by the Double First‐rate Subject‐Food Science and Engineering Program of Hebei Province (2018SPGCA18)Young Tip‐top Talents Plan of Universities and Colleges in Hebei Province of China (BJ2017026)the Specific Foundation for Doctor in Hebei Agriculture University of China (ZD201709)~~
文摘Inefficient charge separation and limited light absorption are two critical issues associated with high‐efficiency photocatalytic H2production using TiO2.Surface defects within a certain concentration range in photocatalyst materials are beneficial for photocatalytic activity.In this study,surface defects(oxygen vacancies and metal cation replacement defects)were induced with a facile and effective approach by surface doping with low‐cost transition metals(Co,Ni,Cu,and Mn)on ultrafine TiO2.The obtained surface‐defective TiO2exhibited a3–4‐fold improved activity compared to that of the original ultrafine TiO2.In addition,a H2production rate of3.4μmol/h was obtained using visible light(λ>420nm)irradiation.The apparent quantum yield(AQY)at365nm reached36.9%over TiO2‐Cu,significantly more than the commercial P25TiO2.The enhancement of photocatalytic H2production activity can be attributed to improved rapid charge separation efficiency andexpanded light absorption window.This hydrothermal treatment with transition metal was proven to be a very facile and effective method for obtaining surface defects.
基金supported by the Engineering and Technology Research Center of Food Preservation,Processing and Safety Control of Liaoning Province,Food Safety Key Lab of Liaoning Province (LNSAKF2011027)Key Laboratory Project of Department of Education of Liaoning Province (2009s004)
文摘TiO2 nanoparticles have been synthesized by using a TiO2@NaCl core-shell structure as the precursor. The surface defects were well preserved by the NaCl shell, and therefore high oxygen adsorption capacity was observed. After the NaC1 shell was removed, the resulting pure TiO2 nanoparticles were of anatase phase and uniform size of around 20-24 nm. The presence of an abundance of surface defects contributes to the high photocatalytic activity of the synthesized materials, and the TiO： mate- rials obtained from the TiO2@NaCl precursor can be used as efficient photocatalysts for degradation of rhodamine B under UV light irradiation.
