Selective synthesis of ethanol from syngas under the Co-based catalysts is still challenging due to the hard of regulating the active site Co^(0) and Co^(2+)ratio.In this work,a series of CaTi_(0.9-x)Co_(x)Mo_(0.1)O_(...Selective synthesis of ethanol from syngas under the Co-based catalysts is still challenging due to the hard of regulating the active site Co^(0) and Co^(2+)ratio.In this work,a series of CaTi_(0.9-x)Co_(x)Mo_(0.1)O_(3)(x=0,0.1-0.4)and CaTi_(0.7)Co_(0.3)O_(3) catalysts were prepared by using citric acid complexation method to promote the synthesis of ethanol.It was found that Mo species in the perovskite lattice can regulate the Co^(0) and Co^(2+)ratio through the domain-limiting effect of perovskite and the degree of Co reduction could be adjusted by changing the Co/Mo molar ratio.Among these investigated catalysts,the total selectivity of alcohols over the catalyst with the optimal Co/Mo ratio CaTi_(0.6)Co_(0.3)Mo_(0.1)O_(3) reached 39.1%,with ethanol accounting for 74.7%,which was ascribed to the moderate and tightly bound ratio of dissociative to non-dissociative adsorption sites on the surface and the balance of CH_(x)-CH_(y) coupling and C^(O) insertion.展开更多
A facile procedure was carried out to prepare macroporous perovskite-type complex oxide catalysts of La1–xKxCo1–yFeyO3(x=0,0.1,y=0,0.1) by using the combined method of organic ligation and solution combustion.This m...A facile procedure was carried out to prepare macroporous perovskite-type complex oxide catalysts of La1–xKxCo1–yFeyO3(x=0,0.1,y=0,0.1) by using the combined method of organic ligation and solution combustion.This method could ensure the formation of the desired macroporous structures and the desired crystal phases of the prepared catalysts.It was found that the macroporous catalysts showed higher catalytic activities for soot combustion than that of the corresponding nanometric samples,and the macroporous ...展开更多
Clean energy and a sustainable environment are grand challenges that the world is facing which can be addressed by converting solar energy into transportable and storable fuels(chemical fuel).The main scientific and t...Clean energy and a sustainable environment are grand challenges that the world is facing which can be addressed by converting solar energy into transportable and storable fuels(chemical fuel).The main scientific and technological challenges for efficient solar energy conversion,energy storage,and environmental applications are the stability,durability,and performance of low-cost functional materials.Among different nanomaterials,perovskite type LaFeO_(3)has been extensively investigated as a photocatalyst due to its abundance,high stability,compositional and structural fexibility,high electrocatalytic activity,efficient sunlight absorption,and tunable band gap and band edges.Hence,it is urgent to write a comprehensive review to highlight the trend,challenges,and prospects of LaFeO_(3)in the field of photocatalytic solar energy conversion and environment purification.This critical review summarizes the history and basic principles of photocatalysis.Further,it reviews in detail the LaFeO_(3),applications,shortcomings,and activity enhancement strategies including the design of nanostructures,elemental doping,and heterojunctions construction such as Type-I,Type-II,Z-Type,and uncommon heterojunctions.Besides,the optical and electronic properties,charge carriers separation,electron transport phenomenon and alignment of the band gaps in LaFeO_(3)-based heterostructures are comprehensively discussed.展开更多
The total conductivity,oxygen sorption property,oxygen permeability and stability of pure perovskite-type oxide BaCo0.7Fe0.2Nb0.1O3-δ (BCFNO) in real operating conditions were investigated. Its total conductivity was...The total conductivity,oxygen sorption property,oxygen permeability and stability of pure perovskite-type oxide BaCo0.7Fe0.2Nb0.1O3-δ (BCFNO) in real operating conditions were investigated. Its total conductivity was measured to be 3.6 S·cm-1 at 600°C. Though the total conductivity of the BCFNO membrane is much smaller than that of the Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCFO) membrane,the oxygen permeability of the BCFNO membrane is similar to that of the BSCFO membrane. SEM observation and EDX analysis of the BCFN...展开更多
Two perovskite-type fluorides K2NaVF6 and （NH4）3VF6 were synthesized under mild hydrothermal con- ditions. The structures of the compounds were determined by means of powder X-ray diffraction analysis. The Riet- vel...Two perovskite-type fluorides K2NaVF6 and （NH4）3VF6 were synthesized under mild hydrothermal con- ditions. The structures of the compounds were determined by means of powder X-ray diffraction analysis. The Riet- veld refinement indicates that K2NaVF6 has a cubic elpasolite-type structure and crystallizes in space group Fm3m with lattice constant a=8.3180（2） nm. （NH4）3VF6 has a cubic cryolite-type structure and crystallizes in space group Fm3m with lattice parameter a=9.090（1） rim. The compounds were further characterized by scanning electron micro- scopy（SEM）, thermogravimetric（TG） and differential thermal analysis（DTA）. The variable temperature magnetic susceptibility of these two compounds was characterized for the first time and the result shows that the magnetic or- dering is related to the crystallographic features and isolated magnetic unit with the temperature decreasing.展开更多
A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCol-xPtxO3/SiO2 （x = 0.03, 0.05, 0.07, 0.09, and 0.10） were prepared through a simple method of ci...A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCol-xPtxO3/SiO2 （x = 0.03, 0.05, 0.07, 0.09, and 0.10） were prepared through a simple method of citrate acid complexa-tion combined with impregnation. In a nanocrystallite of LaCOl-xPtxO3, ions of lanthanum, cobalt, and platinum are evenly mixed at the atomic level and confined within the nanocrystallite. In the reduction process, platinum ions were reduced and migrated onto the surface of the nanocrystallite, and the platinum should be highly dispersed owing to the even mixing of the platinum ions in the precursor. When x = 0.05 or lower, the highest dispersion of Pt could be achieved. The highly dispersed Pt is stable, because of the strong interaction between Pt atoms and the support. The catalysts were characterized by BET surface area, temperature-programmed reduction, X-ray diffraction, transmission electron microscopy, CO temperature-programmed desorption, and turnover frequency. Compared with general precious metal Pt catalysts, the LaCo0.95Pt0.05O3/ SiO2 catalyst exhibited better activity for CO oxidation, and it maintained stability at a high temperature of 400 ℃ for 250 h with complete CO conversion.展开更多
We survey the magnetocaloric effect in perovskite-type oxides （including doped ABO3-type manganese oxides, A3B2OT-type two-layered perovskite oxides, and A2B＇B＇＇O6-type ordered double-perovskite oxides）. Magnetic...We survey the magnetocaloric effect in perovskite-type oxides （including doped ABO3-type manganese oxides, A3B2OT-type two-layered perovskite oxides, and A2B＇B＇＇O6-type ordered double-perovskite oxides）. Magnetic entropy changes larger than those of gadolinium can be observed in polycrystalline La1-xCaxMnO3 and alkali-metal （Na or K） doped La0.8Ca0.2MnO3 perovskite-type manganese oxides. The large magnetic entropy change produced by an abrupt reduction of magnetization is attributed to the anomalous thermal expansion at the Curie temperature. Considerable mag- netic entropy changes can also be observed in two-layered perovskites Lal.6Cal.4Mn207 and La2.5-xK0.5＋xMn2O7＋6 （0 〈 x 〈 0.5）, and double-perovskite Ba2Fe1＋xMol-xO6 （0 〈 x 〈 0.3） near their respective Curie temperatures. Com- pared with rare earth metals and their alloys, the perovskite-type oxides are lower in cost, and they exhibit higher chemical stability and higher electrical resistivity, which together favor lower eddy-current heating. They are potential magnetic refrigerants at high temperatures, especially near room temperature.展开更多
Recent advances in the preparation and application of perovskite-type oxides as bifunctional electrocatalysts for oxygen reaction and oxygen evolution reaction in rechargeable metal-air batteries are presented in this...Recent advances in the preparation and application of perovskite-type oxides as bifunctional electrocatalysts for oxygen reaction and oxygen evolution reaction in rechargeable metal-air batteries are presented in this review.Various fabrication methods of these oxides are introduced in detail,and their advantages and disadvantages are analyzed.Different preparation methods adopted have great influence on the morphologies and physicochemical properties of perovskite-type oxides.As a bifunctional electrocatalyst,perovskite-type oxides are widely used in rechargeable metal-air batteries.The relationship between the preparation methods and the performances of oxygen/air electrodes are summarized.This work is concentrated on the structural stability,the phase compositions,and catalytic performance of perovskite-type oxides in oxygen/air electrodes.The main problems existing in the practical application of perovskite-type oxides as bifunctional electrocatalysts are pointed out and possible research directions in the future are recommended.展开更多
The perovskite-type solid oxides (ABO3) were a novel kind of functional material with superior properties and have found wide application. A series of nanocrystalline mixed oxides LnFexCo1-xO3 (Ln=La, Pr, Sm, Dy, Er)w...The perovskite-type solid oxides (ABO3) were a novel kind of functional material with superior properties and have found wide application. A series of nanocrystalline mixed oxides LnFexCo1-xO3 (Ln=La, Pr, Sm, Dy, Er)were prepared by sol-gel method. Several aspects of the perovskite type LnFexCo1-xO3, such as crystal defects, oxygen ion vacancy, the tolerance factor of the ABO3, col size, and the bond energy of chemical bond, searching for the relationship between the conductivity and structure of the perovskite type LnFexCo1-xO3, hoping to find some regularities in theory, and providing some helps for composing new type of electricity materials.展开更多
Infrared spectra of (n-C_9H_(19)NH_3)_2CuCl_4 in three solid phases were investigated. It was found that the phase transition at T_(cl)(25℃) arises from the change of the interaction and packing structure of the chai...Infrared spectra of (n-C_9H_(19)NH_3)_2CuCl_4 in three solid phases were investigated. It was found that the phase transition at T_(cl)(25℃) arises from the change of the interaction and packing structure of the chain. The phase transition at T_(c2)(34℃)is related to the change of a partial conformational order-disorder. The GTC or GTG' and small concentration of TG structure near CH_3 group exist in phase Ⅲ (above 38℃).展开更多
Layered organic-inorganic hybrids（CnH2n＋1NH3）2（CH3NH3）m-1PbmI3m＋1 containing monolayer（m=1） and bilayer（m=2） perovsikte were synthesized by reactions in solution.The influences of the reactant ratio,solvent,...Layered organic-inorganic hybrids（CnH2n＋1NH3）2（CH3NH3）m-1PbmI3m＋1 containing monolayer（m=1） and bilayer（m=2） perovsikte were synthesized by reactions in solution.The influences of the reactant ratio,solvent,reaction temperature,and reaction time on the structures of the products were investigated.The structures and the properties of the hybrids were characterized using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and ultraviolet and visible（UV） absorption spectroscopy.The XRD patterns and the SEM images demonstrate that the pure bilayer perovskite hybrids are obtained.The UV-vis spectra indicate that the number of the inorganic perovskite layer（m） has greater impact on the band gap than the number of the carbon atoms（n）.The band gap of bilayer hybrids（around 1.9 eV） is significantly less than that of monolayer hybrids（around 2.2 eV）.展开更多
Precursors of La_(1-x)Sr_xFeO_3(x=0.0,0.1,0.4 and 0.6)nanocrystalline materials were prepared by the mixed salts dissolved in an aqueous solution of polyvinyl alcohol(PVA).XRD,DTA and TEM were used to characterize the...Precursors of La_(1-x)Sr_xFeO_3(x=0.0,0.1,0.4 and 0.6)nanocrystalline materials were prepared by the mixed salts dissolved in an aqueous solution of polyvinyl alcohol(PVA).XRD,DTA and TEM were used to characterize the samples. Well-nanocrystalline perovskite-type La_(1_x)Sr_xFeO_3 could be synthesized at the temperatures as low as 400～550℃ for 2h by the calcination of these amorphous precursors,and the calcination of wet LaFeO_3 gel was investigated at 300℃ for lh and 700℃ for 0.5h.展开更多
Iron-based perovskite-type compounds modified by Ru were prepared through sol-gel process to study its catalytic activity of NOx direct decomposition at low temperature and evaluate the conversion of NO under the expe...Iron-based perovskite-type compounds modified by Ru were prepared through sol-gel process to study its catalytic activity of NOx direct decomposition at low temperature and evaluate the conversion of NO under the experimental conditions. The catalytic activity of La 0.9Ce 0.1Fe 0.8-nCo 0.2RunO3 （n=0.01,0.03,0.05,0.07,0.09）series for the NO, NO-CO two components, CO-HC-NO three components were also analyzed. The catalytic investigation evidenced that the presence of Ru is necessary for making highly activity in decomposition of nitric oxide even at low temperature（400 ℃）and La 0.9Ce 0.9Fe 0.75Co 0.2Ru 0.05O3 （n=0.05） has better activity in all the samples, the conversion of it is 58.5%. With the reducing gas（CO,C3H6）added into the gas, the catalyst displayed very high activity in decomposition of NO and the conversion of it is 80% and 92.5% separately.展开更多
Sm-based perovskite-type oxide (SmMeO3: Me = Cr, Mn, Fe, Co) thin-films could be synthesized by a wet-chemical method using an acetylacetone—Poly(Vinyl Pyrrolidone) (PVP) polymeric precursor method at 750℃. The pero...Sm-based perovskite-type oxide (SmMeO3: Me = Cr, Mn, Fe, Co) thin-films could be synthesized by a wet-chemical method using an acetylacetone—Poly(Vinyl Pyrrolidone) (PVP) polymeric precursor method at 750℃. The perovskite-type oxide thin-films were tried to apply an acetylene gas sensor based on AC impedance spectroscopy. Among the oxides tested, SmFeO3 thin-film sensor showed good sensor responses in which the AC impedance at 20 kHz was depending on acetylene gas concentration between 2 ppm and 80 ppm at 400℃.展开更多
Layered organic-inorganic hybrids containing bilayer perovsikte （R-NH3）2（CH3NH3）Pb2I7 （where R=C12H25,C6H5C2H4） were synthesized by reactions in solution. The influences of the solvents and the reactant ratio on...Layered organic-inorganic hybrids containing bilayer perovsikte （R-NH3）2（CH3NH3）Pb2I7 （where R=C12H25,C6H5C2H4） were synthesized by reactions in solution. The influences of the solvents and the reactant ratio on the structures of the products were investigated. The structures and the properties of the hybrids were characterized using X-ray diffraction （XRD） and ultraviolet and visible （UV） adsorption spectra. For comparing with the bilayer perovskite hybrids in structure and band gap magnitude, the hybrids containing monolayer perovskite （R-NH3）2PbI4 were also synthesized and characterized. The results demonstrate that the thickness of inorganic layer has obvious effect on the tunneling magnitude of the band gap but the organic part can be micro actuator of band gap.展开更多
Most of volatile organic compounds （VOCs） are harmful to the atmosphere and human health. Cata‐lytic combustion is an effective way to eliminate VOCs. The key issue is the availability of high per‐formance catalys...Most of volatile organic compounds （VOCs） are harmful to the atmosphere and human health. Cata‐lytic combustion is an effective way to eliminate VOCs. The key issue is the availability of high per‐formance catalysts. Many catalysts including transition metal oxides, mixed metal oxides, and sup‐ported noble metals have been developed. Among these catalysts, the porous ones attract much attention. In this review, we focus on recent advances in the synthesis of ordered mesoporous and macroporous transition metal oxides, perovskites, and supported noble metal catalysts and their catalytic oxidation of VOCs. The porous catalysts outperformed their bulk counterparts. This excel‐lent catalytic performance was due to their high surface areas, high concentration of adsorbed oxy‐gen species, low temperature reducibility, strong interaction between noble metal and support and highly dispersed noble metal nanoparticles and unique porous structures. Catalytic oxidation of carbon monoxide over typical catalysts was also discussed. We made conclusive remarks and pro‐posed future work for the removal of VOCs.展开更多
Increasing concern has been focused on the search for ecofriendly dielectric ceramics to meet the extensive demands of pulsed capacitors.Due to the advantages of high-energy storage density,efficiency,and excellent te...Increasing concern has been focused on the search for ecofriendly dielectric ceramics to meet the extensive demands of pulsed capacitors.Due to the advantages of high-energy storage density,efficiency,and excellent temperature stability,optimization of energy storage performance in dielectric ceramics has been a goal in the past decades.This review summarizes the recently reported progress in energy storage properties of typical perovskite-type lead-free ceramics.The advantages and shortcomings in the various kinds of ceramics are discussed.Finally,future prospects are presented to provide some guidelines for the exploration of new materials.展开更多
Double perovskite-type catalysts including La2 CoMnO6 and La2 CuMnO6 are first evaluated for the effectiveness in removing volatile organic compounds（VOCs）, and single perovskites（La CoO3, LaMnO3, and La Cu O3） ar...Double perovskite-type catalysts including La2 CoMnO6 and La2 CuMnO6 are first evaluated for the effectiveness in removing volatile organic compounds（VOCs）, and single perovskites（La CoO3, LaMnO3, and La Cu O3） are also tested for comparison. All perovskites are tested with the gas hourly space velocity（GHSV） of 30,000 hr^-1, and the temperature range of100–600℃ for C7H8 removal. Experimental results indicate that double perovskites have better activity if compared with single perovskites. Especially, toluene（C7H8） can be completely oxidized to CO2 at 300℃ as La2 Co MnO6 is applied. Characterization of catalysts indicates that double perovskites own unique surface properties and are of higher amounts of lattice oxygen,leading to higher activity. Additionally, apparent activation energy of 68 k J/mol is calculated using Mars-van Krevelen model for C7 H8 oxidation with La2 Co Mn O6 as catalyst. For durability test, both La2 Co Mn O6 and La2 CuMnO6 maintain high C7 H8 removal efficiencies of 100% and98%, respectively, at 300℃ and 30,000 hr^-1, and they also show good resistance to CO2（5%） and H2 O（g）（5%） of the gas streams tested. For various VOCs including isopropyl alcohol（C3H8 O）,ethanal（C2H4O）, and ethylene（C2H4） tested, as high as 100% efficiency could be achieved with double perovskite-type catalysts operated at 300–350℃, indicating that double perovskites are promising catalysts for VOCs removal.展开更多
The key point in CO2 methanation is to improve the activity at low temperature and the stability.For this purpose,a new cerium-modified Ni-La2O3/ZrO2 catalyst was prepared using La1-xCexNiO3/ZrO2 with perovskite phase...The key point in CO2 methanation is to improve the activity at low temperature and the stability.For this purpose,a new cerium-modified Ni-La2O3/ZrO2 catalyst was prepared using La1-xCexNiO3/ZrO2 with perovskite phase as the precursor,which was obtained by citrate complexation combined with an impregnation method.The resulting catalyst was characterized through Nitrogen adsorption and desorption,X-ray diffraction (XRD),Transmission electron microscopy (TEM),Hydrogen temperature programmed reduction (H2-TPR),Temperature-programmed desorption of CO2 (CO2-TPD) and that of H2 (H2-TPD),and X-ray photoelectron spectroscopy (XPS) techniques,and the catalytic performances for CO2 methanation was investigated.Cerium modification could improve the effective activation of CO2,thus enhancing the activity at low temperature for CO2 methanation.The metal Ni nanoparticles prepared using this method were highly dispersed and showed excellent resistance to sintering,leading to very good stability,which could be attributed to the following:Ni nanoparticles could be confined by cerium-modified La2O3;La2O3could be confined by the cerium ions at the La2O3/ZrO2 interface;and the cerium ions were confined by ZrO2.展开更多
Perovskite-type La0.8Sr0.2MnO3 was prepared by stearic acid gel combustion method.The obtained powders were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scaning electron micro...Perovskite-type La0.8Sr0.2MnO3 was prepared by stearic acid gel combustion method.The obtained powders were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scaning electron micrograph(SEM)and X-ray photoelectron spectroscopy(XPS)techniques.The catalytic activity of La0.8Sr0.2MnO3 was investigated on thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)by thermal gravity-differential scanning calorimetry(TG-DSC)techniques.The experimental results show that La0.8Sr0.2MnO3 is an effective catalyst for HMX thermal decomposition.The surface-adsorbed species such as H2O,OH - and adsorbed oxygen(Oad)could result in an advance in the onset temperature of HMX thermal decomposition.The mixture system of Mn 3+ and Mn 4+ ions and lattice oxygen could play key roles for the increase of the decomposition heat of HMX because these exothermic reactions could be catalyzed by La0.8Sr0.2MnO3 between CO and NOx(from the thermal decomposition of HMX)and the oxidation reaction of CO.According to the previous researches and our results,perovskite-type La0.8Sr0.2MnO3 may be used as a novel catalyst or modifier for nitrate ester plasticized polyether(NEPE)propellant.展开更多
基金National Natural Science Foundation of China(21872101,21962014)Science and Technology Program of Zungeer County,Inner Mongolia(2020YY-12)。
文摘Selective synthesis of ethanol from syngas under the Co-based catalysts is still challenging due to the hard of regulating the active site Co^(0) and Co^(2+)ratio.In this work,a series of CaTi_(0.9-x)Co_(x)Mo_(0.1)O_(3)(x=0,0.1-0.4)and CaTi_(0.7)Co_(0.3)O_(3) catalysts were prepared by using citric acid complexation method to promote the synthesis of ethanol.It was found that Mo species in the perovskite lattice can regulate the Co^(0) and Co^(2+)ratio through the domain-limiting effect of perovskite and the degree of Co reduction could be adjusted by changing the Co/Mo molar ratio.Among these investigated catalysts,the total selectivity of alcohols over the catalyst with the optimal Co/Mo ratio CaTi_(0.6)Co_(0.3)Mo_(0.1)O_(3) reached 39.1%,with ethanol accounting for 74.7%,which was ascribed to the moderate and tightly bound ratio of dissociative to non-dissociative adsorption sites on the surface and the balance of CH_(x)-CH_(y) coupling and C^(O) insertion.
基金supported by the National Natural Science Foundation of China (20833011 and 20803093)the 863 Project of China (2006AA06Z346)
文摘A facile procedure was carried out to prepare macroporous perovskite-type complex oxide catalysts of La1–xKxCo1–yFeyO3(x=0,0.1,y=0,0.1) by using the combined method of organic ligation and solution combustion.This method could ensure the formation of the desired macroporous structures and the desired crystal phases of the prepared catalysts.It was found that the macroporous catalysts showed higher catalytic activities for soot combustion than that of the corresponding nanometric samples,and the macroporous ...
基金financially supported by the Ministry of Science and Technology of China(Grant No.2018YFA0702100)the National Natural Science Foundation of China(Grant Nos.11874169,51972129)+3 种基金the National Key R&D Program of China(Grant No.2017YFE0120500)the Key Research and Development Program of Hubei(Grant No.2020BAB079)the South Xinjiang Innovation and Development Program of Key Industries of Xinjiang Production and Construction Corps(Grants No.2020DB002)the Hubei‘‘Chu-Tian Young Scholar”program.
文摘Clean energy and a sustainable environment are grand challenges that the world is facing which can be addressed by converting solar energy into transportable and storable fuels(chemical fuel).The main scientific and technological challenges for efficient solar energy conversion,energy storage,and environmental applications are the stability,durability,and performance of low-cost functional materials.Among different nanomaterials,perovskite type LaFeO_(3)has been extensively investigated as a photocatalyst due to its abundance,high stability,compositional and structural fexibility,high electrocatalytic activity,efficient sunlight absorption,and tunable band gap and band edges.Hence,it is urgent to write a comprehensive review to highlight the trend,challenges,and prospects of LaFeO_(3)in the field of photocatalytic solar energy conversion and environment purification.This critical review summarizes the history and basic principles of photocatalysis.Further,it reviews in detail the LaFeO_(3),applications,shortcomings,and activity enhancement strategies including the design of nanostructures,elemental doping,and heterojunctions construction such as Type-I,Type-II,Z-Type,and uncommon heterojunctions.Besides,the optical and electronic properties,charge carriers separation,electron transport phenomenon and alignment of the band gaps in LaFeO_(3)-based heterostructures are comprehensively discussed.
基金the National High-Tech Research and Development Program of China (No. 2006AA11A189)the Science and Technology Commission of Shanghai Municipality (No. 07DZ12036)+1 种基金the National Engineering Research Center of Advanced Steel Technology (NERCAST, No. 050209)the Education Commission of Shanghai Municipality.
文摘The total conductivity,oxygen sorption property,oxygen permeability and stability of pure perovskite-type oxide BaCo0.7Fe0.2Nb0.1O3-δ (BCFNO) in real operating conditions were investigated. Its total conductivity was measured to be 3.6 S·cm-1 at 600°C. Though the total conductivity of the BCFNO membrane is much smaller than that of the Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCFO) membrane,the oxygen permeability of the BCFNO membrane is similar to that of the BSCFO membrane. SEM observation and EDX analysis of the BCFN...
基金Supported by the Science and Technology Development Planning of Jilin Province,China(Nos.20100116,201105005)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20100061120089)+1 种基金the Open Project of State Key Laboratory of Inorganic Synthesis and Preparative Chemistry(No.2011-01)the Open Project of State Key Laboratory of Superhard Materials(No.2011-04),China
文摘Two perovskite-type fluorides K2NaVF6 and （NH4）3VF6 were synthesized under mild hydrothermal con- ditions. The structures of the compounds were determined by means of powder X-ray diffraction analysis. The Riet- veld refinement indicates that K2NaVF6 has a cubic elpasolite-type structure and crystallizes in space group Fm3m with lattice constant a=8.3180（2） nm. （NH4）3VF6 has a cubic cryolite-type structure and crystallizes in space group Fm3m with lattice parameter a=9.090（1） rim. The compounds were further characterized by scanning electron micro- scopy（SEM）, thermogravimetric（TG） and differential thermal analysis（DTA）. The variable temperature magnetic susceptibility of these two compounds was characterized for the first time and the result shows that the magnetic or- dering is related to the crystallographic features and isolated magnetic unit with the temperature decreasing.
基金supported by the National Natural Science Foundation of China(Nos.21576192,21776214)
文摘A new scheme for the preparation of highly dispersed precious metal catalysts is proposed in this work. Samples of LaCol-xPtxO3/SiO2 （x = 0.03, 0.05, 0.07, 0.09, and 0.10） were prepared through a simple method of citrate acid complexa-tion combined with impregnation. In a nanocrystallite of LaCOl-xPtxO3, ions of lanthanum, cobalt, and platinum are evenly mixed at the atomic level and confined within the nanocrystallite. In the reduction process, platinum ions were reduced and migrated onto the surface of the nanocrystallite, and the platinum should be highly dispersed owing to the even mixing of the platinum ions in the precursor. When x = 0.05 or lower, the highest dispersion of Pt could be achieved. The highly dispersed Pt is stable, because of the strong interaction between Pt atoms and the support. The catalysts were characterized by BET surface area, temperature-programmed reduction, X-ray diffraction, transmission electron microscopy, CO temperature-programmed desorption, and turnover frequency. Compared with general precious metal Pt catalysts, the LaCo0.95Pt0.05O3/ SiO2 catalyst exhibited better activity for CO oxidation, and it maintained stability at a high temperature of 400 ℃ for 250 h with complete CO conversion.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11174132)the National Basic Research Program of China (Grant Nos. 2011CB922102 and 2012CB932304)the Priority Academic Program Development of Jiangsu Higher Education Institutions, China
文摘We survey the magnetocaloric effect in perovskite-type oxides （including doped ABO3-type manganese oxides, A3B2OT-type two-layered perovskite oxides, and A2B＇B＇＇O6-type ordered double-perovskite oxides）. Magnetic entropy changes larger than those of gadolinium can be observed in polycrystalline La1-xCaxMnO3 and alkali-metal （Na or K） doped La0.8Ca0.2MnO3 perovskite-type manganese oxides. The large magnetic entropy change produced by an abrupt reduction of magnetization is attributed to the anomalous thermal expansion at the Curie temperature. Considerable mag- netic entropy changes can also be observed in two-layered perovskites Lal.6Cal.4Mn207 and La2.5-xK0.5＋xMn2O7＋6 （0 〈 x 〈 0.5）, and double-perovskite Ba2Fe1＋xMol-xO6 （0 〈 x 〈 0.3） near their respective Curie temperatures. Com- pared with rare earth metals and their alloys, the perovskite-type oxides are lower in cost, and they exhibit higher chemical stability and higher electrical resistivity, which together favor lower eddy-current heating. They are potential magnetic refrigerants at high temperatures, especially near room temperature.
基金Projects(51504212,21573184,51703061)supported by the National Natural Science Foundation of ChinaProject(2018J01521)supported by the Natural Science Foundation of Fujian Province,ChinaProject(fma2017202)supported by the Open Fund of Fujian Provincial Key Laboratory of Functional Materials and Applications(Xiamen University of Technology),China
文摘Recent advances in the preparation and application of perovskite-type oxides as bifunctional electrocatalysts for oxygen reaction and oxygen evolution reaction in rechargeable metal-air batteries are presented in this review.Various fabrication methods of these oxides are introduced in detail,and their advantages and disadvantages are analyzed.Different preparation methods adopted have great influence on the morphologies and physicochemical properties of perovskite-type oxides.As a bifunctional electrocatalyst,perovskite-type oxides are widely used in rechargeable metal-air batteries.The relationship between the preparation methods and the performances of oxygen/air electrodes are summarized.This work is concentrated on the structural stability,the phase compositions,and catalytic performance of perovskite-type oxides in oxygen/air electrodes.The main problems existing in the practical application of perovskite-type oxides as bifunctional electrocatalysts are pointed out and possible research directions in the future are recommended.
基金the High College-Technology Research Foundation of Shanxi Province (200611022)
文摘The perovskite-type solid oxides (ABO3) were a novel kind of functional material with superior properties and have found wide application. A series of nanocrystalline mixed oxides LnFexCo1-xO3 (Ln=La, Pr, Sm, Dy, Er)were prepared by sol-gel method. Several aspects of the perovskite type LnFexCo1-xO3, such as crystal defects, oxygen ion vacancy, the tolerance factor of the ABO3, col size, and the bond energy of chemical bond, searching for the relationship between the conductivity and structure of the perovskite type LnFexCo1-xO3, hoping to find some regularities in theory, and providing some helps for composing new type of electricity materials.
文摘Infrared spectra of (n-C_9H_(19)NH_3)_2CuCl_4 in three solid phases were investigated. It was found that the phase transition at T_(cl)(25℃) arises from the change of the interaction and packing structure of the chain. The phase transition at T_(c2)(34℃)is related to the change of a partial conformational order-disorder. The GTC or GTG' and small concentration of TG structure near CH_3 group exist in phase Ⅲ (above 38℃).
基金Funded by the National Natural Science Foundation of China(No.51372187)
文摘Layered organic-inorganic hybrids（CnH2n＋1NH3）2（CH3NH3）m-1PbmI3m＋1 containing monolayer（m=1） and bilayer（m=2） perovsikte were synthesized by reactions in solution.The influences of the reactant ratio,solvent,reaction temperature,and reaction time on the structures of the products were investigated.The structures and the properties of the hybrids were characterized using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and ultraviolet and visible（UV） absorption spectroscopy.The XRD patterns and the SEM images demonstrate that the pure bilayer perovskite hybrids are obtained.The UV-vis spectra indicate that the number of the inorganic perovskite layer（m） has greater impact on the band gap than the number of the carbon atoms（n）.The band gap of bilayer hybrids（around 1.9 eV） is significantly less than that of monolayer hybrids（around 2.2 eV）.
文摘Precursors of La_(1-x)Sr_xFeO_3(x=0.0,0.1,0.4 and 0.6)nanocrystalline materials were prepared by the mixed salts dissolved in an aqueous solution of polyvinyl alcohol(PVA).XRD,DTA and TEM were used to characterize the samples. Well-nanocrystalline perovskite-type La_(1_x)Sr_xFeO_3 could be synthesized at the temperatures as low as 400～550℃ for 2h by the calcination of these amorphous precursors,and the calcination of wet LaFeO_3 gel was investigated at 300℃ for lh and 700℃ for 0.5h.
基金Sponsored by the National Natural Science Foundation of China(Grant No.20271019 and 20576027), Natural Science Foundation of Heilongjiang Prov-ince(Grant No.B200504), Postdoctoral Foundationof Heilongjiang Province(Grant No.LBH-Z05066) and Education Department Foundation of Hei-longjiang Province(Grant No.11511270).
文摘Iron-based perovskite-type compounds modified by Ru were prepared through sol-gel process to study its catalytic activity of NOx direct decomposition at low temperature and evaluate the conversion of NO under the experimental conditions. The catalytic activity of La 0.9Ce 0.1Fe 0.8-nCo 0.2RunO3 （n=0.01,0.03,0.05,0.07,0.09）series for the NO, NO-CO two components, CO-HC-NO three components were also analyzed. The catalytic investigation evidenced that the presence of Ru is necessary for making highly activity in decomposition of nitric oxide even at low temperature（400 ℃）and La 0.9Ce 0.9Fe 0.75Co 0.2Ru 0.05O3 （n=0.05） has better activity in all the samples, the conversion of it is 58.5%. With the reducing gas（CO,C3H6）added into the gas, the catalyst displayed very high activity in decomposition of NO and the conversion of it is 80% and 92.5% separately.
文摘Sm-based perovskite-type oxide (SmMeO3: Me = Cr, Mn, Fe, Co) thin-films could be synthesized by a wet-chemical method using an acetylacetone—Poly(Vinyl Pyrrolidone) (PVP) polymeric precursor method at 750℃. The perovskite-type oxide thin-films were tried to apply an acetylene gas sensor based on AC impedance spectroscopy. Among the oxides tested, SmFeO3 thin-film sensor showed good sensor responses in which the AC impedance at 20 kHz was depending on acetylene gas concentration between 2 ppm and 80 ppm at 400℃.
基金National Natural Science Foundation of China(No.50972113)
文摘Layered organic-inorganic hybrids containing bilayer perovsikte （R-NH3）2（CH3NH3）Pb2I7 （where R=C12H25,C6H5C2H4） were synthesized by reactions in solution. The influences of the solvents and the reactant ratio on the structures of the products were investigated. The structures and the properties of the hybrids were characterized using X-ray diffraction （XRD） and ultraviolet and visible （UV） adsorption spectra. For comparing with the bilayer perovskite hybrids in structure and band gap magnitude, the hybrids containing monolayer perovskite （R-NH3）2PbI4 were also synthesized and characterized. The results demonstrate that the thickness of inorganic layer has obvious effect on the tunneling magnitude of the band gap but the organic part can be micro actuator of band gap.
基金supported by the National High Technology Research and Development Program (863 Program,2015AA034603)the National Natural Science Foundation of China (21377008,201077007,20973017)+1 种基金Foundation on the Creative Research Team Construction Promotion Project of Beijing Municipal InstitutionsScientific Research Base Construction-Science and Technology Creation Platform National Materials Research Base Construction~~
文摘Most of volatile organic compounds （VOCs） are harmful to the atmosphere and human health. Cata‐lytic combustion is an effective way to eliminate VOCs. The key issue is the availability of high per‐formance catalysts. Many catalysts including transition metal oxides, mixed metal oxides, and sup‐ported noble metals have been developed. Among these catalysts, the porous ones attract much attention. In this review, we focus on recent advances in the synthesis of ordered mesoporous and macroporous transition metal oxides, perovskites, and supported noble metal catalysts and their catalytic oxidation of VOCs. The porous catalysts outperformed their bulk counterparts. This excel‐lent catalytic performance was due to their high surface areas, high concentration of adsorbed oxy‐gen species, low temperature reducibility, strong interaction between noble metal and support and highly dispersed noble metal nanoparticles and unique porous structures. Catalytic oxidation of carbon monoxide over typical catalysts was also discussed. We made conclusive remarks and pro‐posed future work for the removal of VOCs.
基金supported by the Ministry of Science and Technology of China through the 973–Project under grant(2015CB654601)National Key R&D Program of China(2016YFA0201103)National Natural Science Foundation of China under Grant(No.51772211)and the Instrument Developing Project of Chinese Academy of Sciences(ZDKYYQ20180004).
文摘Increasing concern has been focused on the search for ecofriendly dielectric ceramics to meet the extensive demands of pulsed capacitors.Due to the advantages of high-energy storage density,efficiency,and excellent temperature stability,optimization of energy storage performance in dielectric ceramics has been a goal in the past decades.This review summarizes the recently reported progress in energy storage properties of typical perovskite-type lead-free ceramics.The advantages and shortcomings in the various kinds of ceramics are discussed.Finally,future prospects are presented to provide some guidelines for the exploration of new materials.
基金the Ministry of Science and Technology(MOST),Republic of China(ROC)(No.102WFA0700516)National Central University(No.105G910-9)for fundingfinancial support from the Industrial Technology Research Institute(No.105G910-8)
文摘Double perovskite-type catalysts including La2 CoMnO6 and La2 CuMnO6 are first evaluated for the effectiveness in removing volatile organic compounds（VOCs）, and single perovskites（La CoO3, LaMnO3, and La Cu O3） are also tested for comparison. All perovskites are tested with the gas hourly space velocity（GHSV） of 30,000 hr^-1, and the temperature range of100–600℃ for C7H8 removal. Experimental results indicate that double perovskites have better activity if compared with single perovskites. Especially, toluene（C7H8） can be completely oxidized to CO2 at 300℃ as La2 Co MnO6 is applied. Characterization of catalysts indicates that double perovskites own unique surface properties and are of higher amounts of lattice oxygen,leading to higher activity. Additionally, apparent activation energy of 68 k J/mol is calculated using Mars-van Krevelen model for C7 H8 oxidation with La2 Co Mn O6 as catalyst. For durability test, both La2 Co Mn O6 and La2 CuMnO6 maintain high C7 H8 removal efficiencies of 100% and98%, respectively, at 300℃ and 30,000 hr^-1, and they also show good resistance to CO2（5%） and H2 O（g）（5%） of the gas streams tested. For various VOCs including isopropyl alcohol（C3H8 O）,ethanal（C2H4O）, and ethylene（C2H4） tested, as high as 100% efficiency could be achieved with double perovskite-type catalysts operated at 300–350℃, indicating that double perovskites are promising catalysts for VOCs removal.
基金supported by the National Natural Science Foundation of China(Nos.21872101,21576192)the Natural Science Foundation of Tianjin(18JCZDJC31300)。
文摘The key point in CO2 methanation is to improve the activity at low temperature and the stability.For this purpose,a new cerium-modified Ni-La2O3/ZrO2 catalyst was prepared using La1-xCexNiO3/ZrO2 with perovskite phase as the precursor,which was obtained by citrate complexation combined with an impregnation method.The resulting catalyst was characterized through Nitrogen adsorption and desorption,X-ray diffraction (XRD),Transmission electron microscopy (TEM),Hydrogen temperature programmed reduction (H2-TPR),Temperature-programmed desorption of CO2 (CO2-TPD) and that of H2 (H2-TPD),and X-ray photoelectron spectroscopy (XPS) techniques,and the catalytic performances for CO2 methanation was investigated.Cerium modification could improve the effective activation of CO2,thus enhancing the activity at low temperature for CO2 methanation.The metal Ni nanoparticles prepared using this method were highly dispersed and showed excellent resistance to sintering,leading to very good stability,which could be attributed to the following:Ni nanoparticles could be confined by cerium-modified La2O3;La2O3could be confined by the cerium ions at the La2O3/ZrO2 interface;and the cerium ions were confined by ZrO2.
基金Supported by the National Natural Science Foundation of China （20671084）
文摘Perovskite-type La0.8Sr0.2MnO3 was prepared by stearic acid gel combustion method.The obtained powders were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scaning electron micrograph(SEM)and X-ray photoelectron spectroscopy(XPS)techniques.The catalytic activity of La0.8Sr0.2MnO3 was investigated on thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)by thermal gravity-differential scanning calorimetry(TG-DSC)techniques.The experimental results show that La0.8Sr0.2MnO3 is an effective catalyst for HMX thermal decomposition.The surface-adsorbed species such as H2O,OH - and adsorbed oxygen(Oad)could result in an advance in the onset temperature of HMX thermal decomposition.The mixture system of Mn 3+ and Mn 4+ ions and lattice oxygen could play key roles for the increase of the decomposition heat of HMX because these exothermic reactions could be catalyzed by La0.8Sr0.2MnO3 between CO and NOx(from the thermal decomposition of HMX)and the oxidation reaction of CO.According to the previous researches and our results,perovskite-type La0.8Sr0.2MnO3 may be used as a novel catalyst or modifier for nitrate ester plasticized polyether(NEPE)propellant.
