With hexadecyl trimethyl ammonium bromide(CTAB)as the template,cobaltosic oxide precursors were hydrothermally synthesized.Co_(3)O_(4)catalysts were then prepared by calcining the cobaltosic oxide precursors,which was...With hexadecyl trimethyl ammonium bromide(CTAB)as the template,cobaltosic oxide precursors were hydrothermally synthesized.Co_(3)O_(4)catalysts were then prepared by calcining the cobaltosic oxide precursors,which was further modified by impregnation with K_(2)CO_(3) solution and used in the decomposition of N_(2)O.The catalysts were characterized by means of X-ray diffraction(XRD),nitrogen physisorption,scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),hydrogen temperature-programmed reduction(H_(2)-TPR),and oxygen temperature-programmed desorption(O_(2)-TPD);the effect of CTAB concentration,CTAB/cobalt molar ratio and urea/cobalt molar ratio on the catalytic activity of Co_(3)O_(4)was investigated.The results indicated that the Co_(3)O_(4)catalyst prepared by using 0.05 mol/L CTAB solution,with a CTAB to cobalt molar ratio of 1 and a urea to cobalt molar ratio of 4,exhibits high activity in N_(2)O decomposition.The catalytic performance of Co_(3)O_(4)can be further enhanced by modifying with K.Over the 0.02 K/Co_(3)O_(4)catalyst,the N_(2)O conversion remains over 91%at 400℃after conducting the N_(2)O decomposition reaction for 50 h in the presence of oxygen and steam.展开更多
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
Transition metal oxides are promising candidates for the high-capacity anode material in lithium-ion batteries.The electrochemical performance of transition metal oxides can be improved by constructing suitable compos...Transition metal oxides are promising candidates for the high-capacity anode material in lithium-ion batteries.The electrochemical performance of transition metal oxides can be improved by constructing suitable composite architectures. Herein, we demonstrate a metal–organic framework(MOF)-assisted strategy for the synthesis of a hierarchical hybrid nanostructure composed of Fe_2O_3 nanotubes assembled in Co_3O_4 host. Starting from MOF composite precursors(Fe-based MOF encapsulated in a Cobased host matrix), a complex structure of Co_3O_4 host and engulfed Fe_2O_3 nanotubes was prepared by a simple annealing treatment in air. By virtue of their structural and compositional features, these hierarchical composite particles reveal enhanced lithium storage properties when employed as anodes for lithium-ion batteries.展开更多
基金supported by the Shandong Provincial Natural Science Foundation(ZR2017MB020)Graduate Innovation Foundation of Yantai University(YDZD1816).
文摘With hexadecyl trimethyl ammonium bromide(CTAB)as the template,cobaltosic oxide precursors were hydrothermally synthesized.Co_(3)O_(4)catalysts were then prepared by calcining the cobaltosic oxide precursors,which was further modified by impregnation with K_(2)CO_(3) solution and used in the decomposition of N_(2)O.The catalysts were characterized by means of X-ray diffraction(XRD),nitrogen physisorption,scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),hydrogen temperature-programmed reduction(H_(2)-TPR),and oxygen temperature-programmed desorption(O_(2)-TPD);the effect of CTAB concentration,CTAB/cobalt molar ratio and urea/cobalt molar ratio on the catalytic activity of Co_(3)O_(4)was investigated.The results indicated that the Co_(3)O_(4)catalyst prepared by using 0.05 mol/L CTAB solution,with a CTAB to cobalt molar ratio of 1 and a urea to cobalt molar ratio of 4,exhibits high activity in N_(2)O decomposition.The catalytic performance of Co_(3)O_(4)can be further enhanced by modifying with K.Over the 0.02 K/Co_(3)O_(4)catalyst,the N_(2)O conversion remains over 91%at 400℃after conducting the N_(2)O decomposition reaction for 50 h in the presence of oxygen and steam.
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.
文摘Transition metal oxides are promising candidates for the high-capacity anode material in lithium-ion batteries.The electrochemical performance of transition metal oxides can be improved by constructing suitable composite architectures. Herein, we demonstrate a metal–organic framework(MOF)-assisted strategy for the synthesis of a hierarchical hybrid nanostructure composed of Fe_2O_3 nanotubes assembled in Co_3O_4 host. Starting from MOF composite precursors(Fe-based MOF encapsulated in a Cobased host matrix), a complex structure of Co_3O_4 host and engulfed Fe_2O_3 nanotubes was prepared by a simple annealing treatment in air. By virtue of their structural and compositional features, these hierarchical composite particles reveal enhanced lithium storage properties when employed as anodes for lithium-ion batteries.
