The perovskite type rare earth iron complex (REIC) oxide La 1-x Ce xFeO 3 is designed and prepared as water gas shift catalyst. Activity evaluation and heat resisting test show that the perovskite type compounds La 1-...The perovskite type rare earth iron complex (REIC) oxide La 1-x Ce xFeO 3 is designed and prepared as water gas shift catalyst. Activity evaluation and heat resisting test show that the perovskite type compounds La 1-x Ce xFeO 3(·K) has a good thermal stability if x is less than or equal to 0.5 . But when x is greater than 0.5 , La 1-x Ce xFeO 3(·K) will turn out to be ceria and magnetite partially or completely at high temperature in the shift reaction atmosphere. In the case of x=0.5, the conversion of carbon monoxide is about 68% at 530 ℃. Potassium can greatly improve the low temperature activity, but slightly lower the high temperature activity, and has little impact on the thermal stability. La 0.5 Ce 0.5 FeO 3 (·K) is a promising chromium free high temperature shift catalyst.展开更多
The magnetic functional materials play a particularly important role in our modern society and daily life.The magnetocaloric effect(MCE)is at the basis of a solid state magnetic refrigeration(MR)technology which may e...The magnetic functional materials play a particularly important role in our modern society and daily life.The magnetocaloric effect(MCE)is at the basis of a solid state magnetic refrigeration(MR)technology which may enhance the efficiency of cooling systems,both for room temperature and cryogenic appli-cations.Despite numerous experimental and theoretical MCE studies,commercial MR systems are still at developing stage.Designing magnetic solids with outstanding magnetocaloric performances remains therefore a most urgent task.Herein,recent progresses on characterizing the crystal structure,magnetic properties and cryogenic MCE of rare earths(RE)-based RE_(2)TMTM’O_(6)double perovskite(DP)oxides,where TM and TM’are different 3d transition metals,are summarized.Some Gd-based DP oxides are found to exhibit promising cryogenic magnetocaloric performances which make them attractive for active MR ap-plications.展开更多
Co-salen functionalized on graphene with an average pore size of 27.7 nm as a heterogeneous catalyst exhibited good catalytic activity and recyclability in cyclohexene oxidation.
La1?xSrxCoO3?δ (x=0, 0.4) nanoparticles have been prepared using the citric acid complex-ing-hydrothermal synthesis coupled method and citric acid complexing method. The physico-chemical properties of these materials...La1?xSrxCoO3?δ (x=0, 0.4) nanoparticles have been prepared using the citric acid complex-ing-hydrothermal synthesis coupled method and citric acid complexing method. The physico-chemical properties of these materials were characterized by means of X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), element analysis (EDX), X-ray photoelectron spectroscopic (XPS), oxygen temperature-programmed desorption (O2-TPD), hydrogen temperature-programmed re-duction (H2-TPR) as well as surface area measure-ments and oxidation state titration. Their catalytic performance was examined for the total oxidation of ethylacetate (EA). It is found that the La1?xSrxCoO3?δ (x=0, 0.4) catalysts were single-phase and rhombo-hedrally-structured perovskites and their surface ar-eas ranged from 16 to 26 m2/g. The Sr-doped sample derived from the coupled procedure was uniformly distributed nanoparticles with a short rod-shaped morphology. The doping of Sr (i) enhanced the con-centrations of Co3+ and oxygen vacancies, (ii) in-creased the amount of oxygen adsorbed on the sur-face at low temperatures, (iii) promoted the mobility of lattice oxygen, and (iv) improved the properties of redox. The La0.6Sr0.4CoO2.78 catalyst prepared by the citric acid complexing-hydrothermal synthesis cou-pled strategy performed the best in the oxidation of EA, furthermore no partially oxidized products were formed. Based on the above results, we conclude that in addition to the surface area, the catalytic ac-tivity of the perovskite-type oxide nanoparticles was associated with the structural defect (oxygen vacancy) concentration and redox ability.展开更多
采用柠檬酸络合燃烧法制备了纳米钙钛矿型复合氧化物 AMnO_3(A 为 La,Ce,Pr,Nd)和 La_(0.8)M_(0.2)MnO_3(M 为 K,Cs,Sr)催化剂。采用 X 射线衍射、H_2-程序升温还原和扫描电子显微镜等方法对催化剂试样进行了表征,利用程序升温反应评价...采用柠檬酸络合燃烧法制备了纳米钙钛矿型复合氧化物 AMnO_3(A 为 La,Ce,Pr,Nd)和 La_(0.8)M_(0.2)MnO_3(M 为 K,Cs,Sr)催化剂。采用 X 射线衍射、H_2-程序升温还原和扫描电子显微镜等方法对催化剂试样进行了表征,利用程序升温反应评价了催化剂用于同时消除柴油机尾气中炭颗粒和 NO 的催化活性。研究结果表明,A 位阳离子种类及 A 位掺杂离子的种类对催化剂的活性都有影响。A 位离子为 La 的催化剂(LaMnO_3)活性最好;用低价金属离子部分取代 A 位离子,催化剂活性得到改善,其中以K离子取代效果最好;LaMnO_3和 La_(0.8)K_(0.2)MnO_3催化剂的炭颗粒燃烧温度范围分别为321～521℃和311～425℃,NO 的转化率分别为7.6%和16.4%。展开更多
通过溶胶-凝胶法合成了双钙钛矿型氧化物Sr2Ni0.4Co1.6O6、通过改性Hummers还原方法制备出薄层石墨烯,并制备单一物质和两者复合材料的双功能氧电极,用于测试其氧催化性能。采用XRD、EDS、SEM、FTIR对样品进行表征。结果显示:Sr2Ni0.4Co...通过溶胶-凝胶法合成了双钙钛矿型氧化物Sr2Ni0.4Co1.6O6、通过改性Hummers还原方法制备出薄层石墨烯,并制备单一物质和两者复合材料的双功能氧电极,用于测试其氧催化性能。采用XRD、EDS、SEM、FTIR对样品进行表征。结果显示:Sr2Ni0.4Co1.6O6均匀地分布于薄层石墨烯片层表面。电化学性能测试结果表明:单一Sr2Ni0.4Co1.6O6和薄层石墨烯的氧还原反应(ORR)最大电流密度分别为0.1830、0.1516A/cm2 (–0.6Vvs.Hg/Hg O),氧析出反应(OER)最大电流密度分别为0.2677、0.1174 A/cm2 (1 V vs. Hg/HgO)。当薄层石墨烯添加量占复合催化剂质量的10%时,复合催化剂的氧催化性能最佳,ORR最大电流密度为0.2901 A/cm2(–0.6Vvs.Hg/Hg O),OER最大电流密度为0.3905 A/cm2 (1 V vs. Hg/HgO),明显高于单一催化剂。展开更多
文摘The perovskite type rare earth iron complex (REIC) oxide La 1-x Ce xFeO 3 is designed and prepared as water gas shift catalyst. Activity evaluation and heat resisting test show that the perovskite type compounds La 1-x Ce xFeO 3(·K) has a good thermal stability if x is less than or equal to 0.5 . But when x is greater than 0.5 , La 1-x Ce xFeO 3(·K) will turn out to be ceria and magnetite partially or completely at high temperature in the shift reaction atmosphere. In the case of x=0.5, the conversion of carbon monoxide is about 68% at 530 ℃. Potassium can greatly improve the low temperature activity, but slightly lower the high temperature activity, and has little impact on the thermal stability. La 0.5 Ce 0.5 FeO 3 (·K) is a promising chromium free high temperature shift catalyst.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52171174 and 91963123)the Ten Thousand Talents Plan of Zhejiang Province(No.2018R52003)the Fundamental Research Funds for the Provincial University of Zhejiang(No.GK199900299012-022).
文摘The magnetic functional materials play a particularly important role in our modern society and daily life.The magnetocaloric effect(MCE)is at the basis of a solid state magnetic refrigeration(MR)technology which may enhance the efficiency of cooling systems,both for room temperature and cryogenic appli-cations.Despite numerous experimental and theoretical MCE studies,commercial MR systems are still at developing stage.Designing magnetic solids with outstanding magnetocaloric performances remains therefore a most urgent task.Herein,recent progresses on characterizing the crystal structure,magnetic properties and cryogenic MCE of rare earths(RE)-based RE_(2)TMTM’O_(6)double perovskite(DP)oxides,where TM and TM’are different 3d transition metals,are summarized.Some Gd-based DP oxides are found to exhibit promising cryogenic magnetocaloric performances which make them attractive for active MR ap-plications.
基金the National Natural Science Foundation of China(20973079 and U1162201)Graduate Innovation Fund of Jilin University(20121051)
文摘Co-salen functionalized on graphene with an average pore size of 27.7 nm as a heterogeneous catalyst exhibited good catalytic activity and recyclability in cyclohexene oxidation.
基金This work was supported by the Key Project of Science and Technology Development Plan of the Education Committee of Beijing and the Key Project （Class B） of Natural Science Foundation of Beijing （Grant No. KZ200610005004）.
文摘La1?xSrxCoO3?δ (x=0, 0.4) nanoparticles have been prepared using the citric acid complex-ing-hydrothermal synthesis coupled method and citric acid complexing method. The physico-chemical properties of these materials were characterized by means of X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), element analysis (EDX), X-ray photoelectron spectroscopic (XPS), oxygen temperature-programmed desorption (O2-TPD), hydrogen temperature-programmed re-duction (H2-TPR) as well as surface area measure-ments and oxidation state titration. Their catalytic performance was examined for the total oxidation of ethylacetate (EA). It is found that the La1?xSrxCoO3?δ (x=0, 0.4) catalysts were single-phase and rhombo-hedrally-structured perovskites and their surface ar-eas ranged from 16 to 26 m2/g. The Sr-doped sample derived from the coupled procedure was uniformly distributed nanoparticles with a short rod-shaped morphology. The doping of Sr (i) enhanced the con-centrations of Co3+ and oxygen vacancies, (ii) in-creased the amount of oxygen adsorbed on the sur-face at low temperatures, (iii) promoted the mobility of lattice oxygen, and (iv) improved the properties of redox. The La0.6Sr0.4CoO2.78 catalyst prepared by the citric acid complexing-hydrothermal synthesis cou-pled strategy performed the best in the oxidation of EA, furthermore no partially oxidized products were formed. Based on the above results, we conclude that in addition to the surface area, the catalytic ac-tivity of the perovskite-type oxide nanoparticles was associated with the structural defect (oxygen vacancy) concentration and redox ability.
文摘采用柠檬酸络合燃烧法制备了纳米钙钛矿型复合氧化物 AMnO_3(A 为 La,Ce,Pr,Nd)和 La_(0.8)M_(0.2)MnO_3(M 为 K,Cs,Sr)催化剂。采用 X 射线衍射、H_2-程序升温还原和扫描电子显微镜等方法对催化剂试样进行了表征,利用程序升温反应评价了催化剂用于同时消除柴油机尾气中炭颗粒和 NO 的催化活性。研究结果表明,A 位阳离子种类及 A 位掺杂离子的种类对催化剂的活性都有影响。A 位离子为 La 的催化剂(LaMnO_3)活性最好;用低价金属离子部分取代 A 位离子,催化剂活性得到改善,其中以K离子取代效果最好;LaMnO_3和 La_(0.8)K_(0.2)MnO_3催化剂的炭颗粒燃烧温度范围分别为321～521℃和311～425℃,NO 的转化率分别为7.6%和16.4%。
文摘通过溶胶-凝胶法合成了双钙钛矿型氧化物Sr2Ni0.4Co1.6O6、通过改性Hummers还原方法制备出薄层石墨烯,并制备单一物质和两者复合材料的双功能氧电极,用于测试其氧催化性能。采用XRD、EDS、SEM、FTIR对样品进行表征。结果显示:Sr2Ni0.4Co1.6O6均匀地分布于薄层石墨烯片层表面。电化学性能测试结果表明:单一Sr2Ni0.4Co1.6O6和薄层石墨烯的氧还原反应(ORR)最大电流密度分别为0.1830、0.1516A/cm2 (–0.6Vvs.Hg/Hg O),氧析出反应(OER)最大电流密度分别为0.2677、0.1174 A/cm2 (1 V vs. Hg/HgO)。当薄层石墨烯添加量占复合催化剂质量的10%时,复合催化剂的氧催化性能最佳,ORR最大电流密度为0.2901 A/cm2(–0.6Vvs.Hg/Hg O),OER最大电流密度为0.3905 A/cm2 (1 V vs. Hg/HgO),明显高于单一催化剂。
