In the present study,we synthesized CeO2 catalysts doped with various transition metals(M=Co,Fe,or Cu)using a supercritical water hydrothermal route,which led to the incorporation of the metal ions in the CeO2 lattice...In the present study,we synthesized CeO2 catalysts doped with various transition metals(M=Co,Fe,or Cu)using a supercritical water hydrothermal route,which led to the incorporation of the metal ions in the CeO2 lattice,forming solid solutions.The catalysts were then used for the selective catalytic reduction(SCR)of NO by CO.The Cu‐doped catalyst exhibited the highest SCR activity;it had a T50(i.e.,50%NO conversion)of only 83°C and a T90(i.e.,90%NO conversion)of 126°C.Such an activity was also higher than in many state‐of‐the‐art catalysts.In situ diffuse reflectance Fourier transform infrared spectroscopy suggested that the MOx‐CeO2 catalysts(M=Co and Fe)mainly followed an Eley‐Rideal reaction mechanism for CO‐SCR.In contrast,a Langmuir‐Hinshelwood SCR reaction mechanism occurred in CuO‐CeO2 owing to the presence of Cu+species,which ensured effective adsorption of CO.This explains why CuO‐CeO2 exhibited the highest activity with regard to the SCR of NO by CO.展开更多
Copper–ceria(Cu O–CeO2) catalysts have been known to be very effective for the oxidation of CO, and their chemical behavior has been extensively studied during the last decades. However, the effect of different CeO2...Copper–ceria(Cu O–CeO2) catalysts have been known to be very effective for the oxidation of CO, and their chemical behavior has been extensively studied during the last decades. However, the effect of different CeO2 crystal surfaces on the catalytic activity of Cu O–CeO2 for the oxidation of CO is still unclear and should be further elucidated. In this study, we deposited 1 wt% Cu on mostly {100}-exposed CeO2 nanocubes(1 Cu Ce NC) and mostly {110}-exposed CeO2 nanorods(1 Cu Ce NR), respectively. Both 1 Cu Ce NC and 1 Cu Ce NR have been used as catalysts for the oxidation of CO and achieved 100% and 50% CO conversion at 130 ℃, respectively. The differences in the catalytic activity of 1 Cu Ce NC and 1 Cu Ce NR were analyzed using temperature-programmed reduction of H2 and temperature-programmed desorption of CO techniques. The results confirmed the excellent reducibility of the 1 Cu Ce NC catalyst, which was attributed to the weak interactions between Cu and the CeO2 support. Moreover, in situ diffuse reflectance infrared Fourier-transform spectroscopy studies indicated that the {100} planes of 1 Cu Ce NC facilitated the generation of active Cu(I) sites, which resulted in the formation of highly reactive Cu(I)-CO species during the oxidation of CO. Both the excellent redox properties and effective CO adsorption capacity of the 1 Cu Ce NC catalyst increased its catalytic reactivity.展开更多
Co/Al2O3 Fischer-Tropsch synthesis catalysts with different cobalt loadings were prepared using incipient wetness impregnation method. The effects of cobalt loading on the properties of catalysts were studied by means...Co/Al2O3 Fischer-Tropsch synthesis catalysts with different cobalt loadings were prepared using incipient wetness impregnation method. The effects of cobalt loading on the properties of catalysts were studied by means of X-ray diffraction （XRD）, temperature programmed reduction （TPR）, hydrogen temperature programmed desorption （H2-TPD） and O2 titration. Co-support compound formation can be detected in catalyst system by XRD. For the Co/Al2O3 catalysts with low cobalt loading, CoAl2O4 phase appears visibly. Two different reduction regions can be presented for Co/Al2O3 catalysts, which belong to Co3O4 crystallites （reduction at 320 ℃） and cobalt oxide-alumina interaction species （reduction at above 400 ℃）. Increasing Co loading results in the increase of Co3O4 crystallite size. The reduced Co/Al2O3 catalysts have two adsorption sites, and cobalt loading greatly influences the adsorption behavior. With the increase of cobalt loading, the amount of low temperature adsorption is increased, the amount of high temperature adsorption is decreased, and the percentage reduction and cobalt crystallite size are increased.展开更多
Among all CO2 electroreduction products,methane(CH4)and ethylene(C_(2)H_(4))are two typical and valuable hydrocarbon products which are formed in two different pathways:hydrogenation and dimerization reactions of the ...Among all CO2 electroreduction products,methane(CH4)and ethylene(C_(2)H_(4))are two typical and valuable hydrocarbon products which are formed in two different pathways:hydrogenation and dimerization reactions of the same CO intermediate.Theoretical studies show that the adsorption configurations of CO intermediate determine the reaction pathways towards CH4/C_(2)H_(4).However,it is challenging to experimentally control the CO adsorption configurations at the catalyst surface,and thus the hydrocarbon selectivity is still limited.Herein,we seek to synthesize two well-defined copper nanocatalysts with controllable surface structures.The two model catalysts exhibit a high hydrocarbon selectivity toward either CH4(83%)or C_(2)H_(4)(93%)under identical reduction conditions.Scanning transmission electron microscopy and X-ray absorption spectroscopy characterizations reveal the low-coordination Cu^(0)sites and local Cu^(0)/Cu^(+)sites of the two catalysts,respectively.CO-temperature programed desorption,in-situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory studies unveil that the bridge-adsorbed CO(CO_(B))on the low-coordination Cu^(0)sites is apt to be hydrogenated to CH4,whereas the bridge-adsorbed CO plus linear-adsorbed CO(CO_(B)+CO_(L))on the local Cu^(0)/Cu^(+)sites are apt to be coupled to C_(2)H_(4).Our findings pave a new way to design catalysts with controllable CO adsorption configurations for high hydrocarbon product selectivity.展开更多
文摘In the present study,we synthesized CeO2 catalysts doped with various transition metals(M=Co,Fe,or Cu)using a supercritical water hydrothermal route,which led to the incorporation of the metal ions in the CeO2 lattice,forming solid solutions.The catalysts were then used for the selective catalytic reduction(SCR)of NO by CO.The Cu‐doped catalyst exhibited the highest SCR activity;it had a T50(i.e.,50%NO conversion)of only 83°C and a T90(i.e.,90%NO conversion)of 126°C.Such an activity was also higher than in many state‐of‐the‐art catalysts.In situ diffuse reflectance Fourier transform infrared spectroscopy suggested that the MOx‐CeO2 catalysts(M=Co and Fe)mainly followed an Eley‐Rideal reaction mechanism for CO‐SCR.In contrast,a Langmuir‐Hinshelwood SCR reaction mechanism occurred in CuO‐CeO2 owing to the presence of Cu+species,which ensured effective adsorption of CO.This explains why CuO‐CeO2 exhibited the highest activity with regard to the SCR of NO by CO.
文摘Copper–ceria(Cu O–CeO2) catalysts have been known to be very effective for the oxidation of CO, and their chemical behavior has been extensively studied during the last decades. However, the effect of different CeO2 crystal surfaces on the catalytic activity of Cu O–CeO2 for the oxidation of CO is still unclear and should be further elucidated. In this study, we deposited 1 wt% Cu on mostly {100}-exposed CeO2 nanocubes(1 Cu Ce NC) and mostly {110}-exposed CeO2 nanorods(1 Cu Ce NR), respectively. Both 1 Cu Ce NC and 1 Cu Ce NR have been used as catalysts for the oxidation of CO and achieved 100% and 50% CO conversion at 130 ℃, respectively. The differences in the catalytic activity of 1 Cu Ce NC and 1 Cu Ce NR were analyzed using temperature-programmed reduction of H2 and temperature-programmed desorption of CO techniques. The results confirmed the excellent reducibility of the 1 Cu Ce NC catalyst, which was attributed to the weak interactions between Cu and the CeO2 support. Moreover, in situ diffuse reflectance infrared Fourier-transform spectroscopy studies indicated that the {100} planes of 1 Cu Ce NC facilitated the generation of active Cu(I) sites, which resulted in the formation of highly reactive Cu(I)-CO species during the oxidation of CO. Both the excellent redox properties and effective CO adsorption capacity of the 1 Cu Ce NC catalyst increased its catalytic reactivity.
文摘Co/Al2O3 Fischer-Tropsch synthesis catalysts with different cobalt loadings were prepared using incipient wetness impregnation method. The effects of cobalt loading on the properties of catalysts were studied by means of X-ray diffraction （XRD）, temperature programmed reduction （TPR）, hydrogen temperature programmed desorption （H2-TPD） and O2 titration. Co-support compound formation can be detected in catalyst system by XRD. For the Co/Al2O3 catalysts with low cobalt loading, CoAl2O4 phase appears visibly. Two different reduction regions can be presented for Co/Al2O3 catalysts, which belong to Co3O4 crystallites （reduction at 320 ℃） and cobalt oxide-alumina interaction species （reduction at above 400 ℃）. Increasing Co loading results in the increase of Co3O4 crystallite size. The reduced Co/Al2O3 catalysts have two adsorption sites, and cobalt loading greatly influences the adsorption behavior. With the increase of cobalt loading, the amount of low temperature adsorption is increased, the amount of high temperature adsorption is decreased, and the percentage reduction and cobalt crystallite size are increased.
基金supported by the National Natural Science Foundation of China (21875042)Shanghai Science and Technology Committee (18QA1400800)+1 种基金the Program of Eastern Scholar at Shanghai Institutions and Yanchang Petroleum Groupsupported by the Frontier Research Center for Materials Structure, School of Materials Science and Engineering of Shanghai Jiao Tong University
文摘Among all CO2 electroreduction products,methane(CH4)and ethylene(C_(2)H_(4))are two typical and valuable hydrocarbon products which are formed in two different pathways:hydrogenation and dimerization reactions of the same CO intermediate.Theoretical studies show that the adsorption configurations of CO intermediate determine the reaction pathways towards CH4/C_(2)H_(4).However,it is challenging to experimentally control the CO adsorption configurations at the catalyst surface,and thus the hydrocarbon selectivity is still limited.Herein,we seek to synthesize two well-defined copper nanocatalysts with controllable surface structures.The two model catalysts exhibit a high hydrocarbon selectivity toward either CH4(83%)or C_(2)H_(4)(93%)under identical reduction conditions.Scanning transmission electron microscopy and X-ray absorption spectroscopy characterizations reveal the low-coordination Cu^(0)sites and local Cu^(0)/Cu^(+)sites of the two catalysts,respectively.CO-temperature programed desorption,in-situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory studies unveil that the bridge-adsorbed CO(CO_(B))on the low-coordination Cu^(0)sites is apt to be hydrogenated to CH4,whereas the bridge-adsorbed CO plus linear-adsorbed CO(CO_(B)+CO_(L))on the local Cu^(0)/Cu^(+)sites are apt to be coupled to C_(2)H_(4).Our findings pave a new way to design catalysts with controllable CO adsorption configurations for high hydrocarbon product selectivity.
