In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1- SrxMO3-λ (M=Fe, x ...In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1- SrxMO3-λ (M=Fe, x Mn) perovskite oxides instead of molecular oxygen was investigated. The redox circulation between 11% O2/Ar flow and 11% CH4/He flow at 900℃ shows that methane can be oxidized to CO and H2 with a selectivity of over 90.7% using the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite oxides in an appropriate reaction condition, while the lost lattice x oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite x oxides instead of molecular oxygen to react with methane to synthesis gas in the redox mode.展开更多
Single-phase perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ has been successfully prepared by using citrate-EDTA complexation method at relatively low calcination temperature. The structure and thermal decomposition process of ...Single-phase perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ has been successfully prepared by using citrate-EDTA complexation method at relatively low calcination temperature. The structure and thermal decomposition process of the complex precursor have been investigated by means of differential scanning calorimetry-thermal gravimetric analysis (DSC/TGA), X-ray diffraction (XRD), and Fourier transform infrared spectroscopic (FT-IR) measurements. The precursor decomposed completely and started to form perovskite-type oxide above 420 ℃ according to the differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results. Single-phase perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ obtained has been confirmed from the XRD pattern, and no peak of SrCO3 was found by XRD of the oxides synthesized at a relatively low temperature of 800℃. The reducibility of La0.6Sr0.4Co0.8Fe0.2O3-δ was also characterized by the temperature programmed reduction (TPR) technique. Disk shaped dense La0.6Sr0.4Co0.8Fe0.2O3-δ membrane was prepared by the isostatical pressing method. The oxygen flux rate of dense La0.6Sr0.4Co0.8Fe0.2O3-δ membrane was (2.8-18)× 10^-8 mol/(cm^2.s) in the temperature range of 800-1000 ℃.展开更多
The synthesis process for La 1- x Sr x Mn 1- y Co y O 3- δ ( x = 0.2, 0.3; y = 0.2, 0.8, designated as LSMC below) perovskite oxides prepared by solid state reaction was investigated using DSC/TG, XRD, EPMA and parti...The synthesis process for La 1- x Sr x Mn 1- y Co y O 3- δ ( x = 0.2, 0.3; y = 0.2, 0.8, designated as LSMC below) perovskite oxides prepared by solid state reaction was investigated using DSC/TG, XRD, EPMA and particle size analysis methods. It was found that LSMCs were all of single phase and the synthesis process might be divided into three stages: the decomposition of reactants, the formation of LaMn(Co)O 3 based oxides, and the formation of LSMC solid solution. Typical average and the peak value of particle size, and the specific surface area are 14.65?μm, 16.4?μm and 1.38?m 2/mL, respectively, for mixed reactants and are 23.81?μm, 32.11?μm and 0.5?m 2/mL, respectively, for powder synthesized at 1?200?℃ for 8?h in air.展开更多
Cobalt-free oxides GdxBal-xFeO3-σas(0.01 _〈 x _〈 0.1 ) were achieved by a solid state reaction method. It is found that GdxBal-xFeO3-σas(0.025 _〈 x _〈 0.1) exhibits the cubic perovskite structure. Among GdxB...Cobalt-free oxides GdxBal-xFeO3-σas(0.01 _〈 x _〈 0.1 ) were achieved by a solid state reaction method. It is found that GdxBal-xFeO3-σas(0.025 _〈 x _〈 0.1) exhibits the cubic perovskite structure. Among GdxBal-xFeO3-σas (0.025 -〈 x -〈 0.1 ), the GdxBal-xFeO3-σas (GBF2.5) membrane shows the outstanding phase structure stability and the highest oxygen permeation, which can reach 1.44 ml. cm- 2. rain- 1 at 950 ℃ under air/He oxygen partial pressure gradient. The GBF2.5 membrane was successfully operated for more than 100 h at 800 ℃ and the oxygen permeation flux through the membrane is 0.62 ml. cm- 2. rain- 1. After 100 h oxygen permeation experiment at 800℃, X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDXS) demonstrate that the GBF2.5 exhibits phase structure stability even at intermediate temoerature.展开更多
Among the perovskite-type oxides with symmetrical structure applied in oxygen permeable membranes, cubic phase structure is the most favorable for oxygen permeation. In order to stabilize the cubic perovskite structur...Among the perovskite-type oxides with symmetrical structure applied in oxygen permeable membranes, cubic phase structure is the most favorable for oxygen permeation. In order to stabilize the cubic perovskite structure of BaFeO3-δ material at room temperature, iron was partially substituted by praseodymium. BaFe1-yPryO3-δ powders were synthesized by a solid state reaction method, and sintered samples were prepared from the synthesized BaFe1-yPryO3-δ powders. X-ray diffraction results reveal that the BaFe1-yPryO3-δ samples remain cubic structure at praseodymium substitution amount of y 0.05, 0.075, 0.1. Scanning electron microscope observation indicates that the sintered samples contain only a small amount of enclosed pores and the grain size of BaFe1-yPryO3-δ increase monotonically with the increase of the praseodymium doping amount, praseodymium doping promotes the grain size growth. Tests of electrical conductivity and oxygen permeation flux show that praseodymium doping improves the conduction properties of BaFe1-yPryO3-δ and BaFe0.9Pr0.1O3-δ composition has an electrical conductivity of 6.5 S/era and an oxygen permeation of 1.112 mL/(cm^2.min) at 900 ℃, respectively. High temperature XRD in- vestigation shows that the crystal structure of BaFe0.975Pr0.025O3-δ membrane completely transform to cubic phase at 700℃. The present test results have shown that partially substitution of Fe by praseodymium in BaFeO3 can stabilize the cubic structure and improve the properties.展开更多
Due to the unique structure of perovskite materials,their capacitance can be improved by introducing oxygen vacancy.In this paper,the LaMnO3-δ material containing oxygen vacancy was synthesized by molten salt method ...Due to the unique structure of perovskite materials,their capacitance can be improved by introducing oxygen vacancy.In this paper,the LaMnO3-δ material containing oxygen vacancy was synthesized by molten salt method in KNO3-NaNO3-NaNO2 melt.The La-Mn-O crystal grows gradually in molten salt with the increase of temperature.It was confirmed that LaMnO3-δ with perovskite structure and incomplete oxygen content were synthesized by molten salt method and presented a three-dimensional shape.LaMnO3-δ stores energy by redox reaction and adsorption of OH-in electrolyte simultaneously.In comparison with the stoichiometric LaMnO3 prepared by the sol-gel method,LaMnO3-δ prepared by molten salt method proffered higher capacitance and better performance.The galvanostatic charge-discharge curve showed specific capacitance of 973.5 F/g under current density of 1 A/g in 6 M KOH.The capacitance of LaMn03-δ was 82.7%under condition of 5 A/g compared with the capacitance at the current of 1A/g,and the specific capacitances of 648.0 and 310.0 F/g were obtained after 2000 and 5000 cycles of galvanostatic charging-discharging,respectively.Molten salt synthesis method is relatively simple and suitable for industrial scale,presenting a promising prospect in the synthesis of perovskite oxide materials.展开更多
LaNi(0.6)Fe(0.4)O(3-δ) (LNF) powders were synthesized by the glycine-nitrate process and LNF-gadolinium-doped ceria (GDC) nanocomposite cathodes for solid oxide fuel cells (SOFCs) were fabricated by infil...LaNi(0.6)Fe(0.4)O(3-δ) (LNF) powders were synthesized by the glycine-nitrate process and LNF-gadolinium-doped ceria (GDC) nanocomposite cathodes for solid oxide fuel cells (SOFCs) were fabricated by infiltration from LNF porous backbones. Electrochemical properties and Cr-poisoning behavior of LNF-GDC cathodes were studied. Single phase perovskite LNF could be obtained at the glycine to nitrate molar ratio of 1:1. The polarization resistance of the LNF-GDC nanocomposite cathode was significantly decreased in comparison with the LNF. This phenomenon was associated with enhanced catalytic activity and enlarged triple-phase boundary (TPB) length by GDC nano particles. In addition, the nanocomposite cathode showed good Cr tolerance under open circuit condition. The LNF-GDC nanocomposite cathodes were expected for use as a potential cathode in intermediate- temperature solid oxide fuel cells (IT-SOFC).展开更多
BaFeO_(3-δ)-derived perovskites are promising cathodes for intermediate temperature solid oxide fuel cells.The activity of these perovskites depends on the number of oxygen vacancies in their lattice,which can be tun...BaFeO_(3-δ)-derived perovskites are promising cathodes for intermediate temperature solid oxide fuel cells.The activity of these perovskites depends on the number of oxygen vacancies in their lattice,which can be tuned by cationic substitution.Our first-principle calculations show that Ag is a promising substitute for the Fe site,resulting in a reduced oxygen vacancy formation energy compared with the pristine BaFeO_(3-δ).Ag has limited solubility in perovskites,and its introduction generates an Ag metal secondary phase,which influences the cathode performances.In this work,we investigate the matter,using a Ba0:9La0:1Fe_(1-x)AgxO_(3-δ)series of materials as a case study.Acknowledging the limited solubility of Ag in Ba0:9La0:1Fe_(1-x)AgxO_(3-δ),we aim to distinguish the effects of Ag substitution from those of the Ag secondary phase.We observed that Ag substitution increases the number of oxygen vacancies,confirming our calculations,and facilitates the oxygen incorporation.However,Ag substitution lowers the number of holes,in this way reducing the electronic p-type conductivity.On the other hand,Ag metal positively affects the electronic conductivity and helps the redistribution of the electronic charge at the cathode-electrolyte interface.展开更多
Perovskite SrVO_(3) has been investigated as a promising lithium storage anode where the V cation plays the role of the redox center,combining excellent cycle stability and safe operating potential versus Li metal pla...Perovskite SrVO_(3) has been investigated as a promising lithium storage anode where the V cation plays the role of the redox center,combining excellent cycle stability and safe operating potential versus Li metal plating,with limited capacity.Here,we demonstrate the possibility to boost the lithium storage properties,by reducing the non-redox active Sr cation content and fine-tuning the O anion vacancies while maintaining a non-stoichiometric Sr_(x)VO_(3-δ) perovskite structure.Theoretical investigations suggest that Sr vacancy can work as favorable Li^(+) storage sites and preferential transport channels for guest Li^(+) ions,contributing to the increased specific capacity and rate performance.In contrast,inducing O anion vacancy in Sr_(x)VO_(3-δ) can improve rate performance while compromising the specific capacity.Our experimental results confirm the enhancement of specific capacities by fine adjusting the Sr and O vacancies,with a maximum capacity of 444 mAh g^(-1) achieved with Sr_(0.63)VO_(3-δ),which is a 37%increase versus stoichiometric SrVO_(3).Although rich defects have been induced,Sr_(x)VO_(3-δ) electrodes maintain a stable perovskite structure during cycling versus a LiFePO_(4) cathode,and the full-cell could achieve more than 6000 discharge/charge cycles with 80%capacity retention.This result highlights the possibility to use the cation defective-based engineering approach to design high-capacity perovskite oxide anode materials.展开更多
Perovskite oxide La_(0.6)Ca_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)(LCFN)has been used in symmetric solid oxide cells(SSOCs)to obtain good electrochemical performance in both fuel cells(SOFCs)and electrolysis cells(SOECs)modes....Perovskite oxide La_(0.6)Ca_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)(LCFN)has been used in symmetric solid oxide cells(SSOCs)to obtain good electrochemical performance in both fuel cells(SOFCs)and electrolysis cells(SOECs)modes.However,its structural stability still faces challenges and the electrocatalytic activity also needs to be further improved.Herein,tungsten-doped La_(0.6)Ca_(0.4)Fe_(0.7)Ni_(0.2)W_(0.1)0_(3-δ)(LCFNW)perovskite oxide material was synthesized which exhibits good structural stability under H_(2)and superior electrochemical performance as an electrode for SSOCs.In SOFCs mode,the cell achieved the maximum power density of 0.58 W·cm^(-2)with wet H_(2)as fuel at 850℃.In SOECs mode,the current density can reach 1.81 A·cm^(-2)for pure CO_(2)electrolysis at 2 V.Moreover,the SSOCs exhibits outstanding long-term stability in both SOFCs and SOECs modes,proving that doping W in perovskite oxide is an effective strategy to enhance the catalytic activity and stability of the electrode.The LCFNW material developed in this work shows promising prospect as an electrode candidate for SSOCs.展开更多
La0.15Sr0.85Ga0.3Fe0.7O3-δ (LSGFO) and La0.15Sr0.85Co0.3Fe0.7O3-δ (LSCFO) mixed oxygenion and electron conducting oxides were synthesized by using a combined EDTA and citrate complexing method, and the corresponding...La0.15Sr0.85Ga0.3Fe0.7O3-δ (LSGFO) and La0.15Sr0.85Co0.3Fe0.7O3-δ (LSCFO) mixed oxygenion and electron conducting oxides were synthesized by using a combined EDTA and citrate complexing method, and the corresponding dense membranes were fabricated. The properties of the oxide powders and membranes were characterized with combined SEM, XRD, H2-TPR, O2-TPD techniques, mechanical strength and oxygen permeation measurement. The results showed that LSGFO had much higher thermochemical stability than LSCFO due to the higher valence stability of Ga3+. After the temperature-programmed reduction by 5% H2 in Ar from 20°C to 1020°C, the basic perovskite structure of LSGFO was successfully preserved. LSGFO also favors the oxygen vacancy formation better than LSCFO. Oxygen permeation measurement demonstrated that LSGFO had higher oxygen permeation flux than LSCFO, but they had similar activation energy for oxygen transportation, with a value of 110 and 117 kJ · mol-1, respectively. The difference in oxygen permeation fluxes was correlated with the difference in oxygen vacancy concentrations for the two materials.展开更多
The permeability and stability of Sm_(0.7)Sr_(0.3)CoO_(3-δ)(SSCO) regarding the special requirements for carbon capture and storage(CCS) application were investigated.Pure CO_ was used as the sweep gas at 9...The permeability and stability of Sm_(0.7)Sr_(0.3)CoO_(3-δ)(SSCO) regarding the special requirements for carbon capture and storage(CCS) application were investigated.Pure CO_ was used as the sweep gas at 900 °C,leading to that the oxygen permeation flux decreases by about 34 %.Several cycles of changing the sweep gas between helium and CO_2 indicate the good reversibility of this degradation.Both carbonate formation and adsorption of CO_2 on the membrane surface are responsible for the degradation of the membrane performance.The better CO_2 resistance results from the substitution of Sm for Sr due to the higher acidity of Sm_2O_3(1.278) than that of Sr O(0.978) and a discontinuous layer of carbonate.展开更多
文摘In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1- SrxMO3-λ (M=Fe, x Mn) perovskite oxides instead of molecular oxygen was investigated. The redox circulation between 11% O2/Ar flow and 11% CH4/He flow at 900℃ shows that methane can be oxidized to CO and H2 with a selectivity of over 90.7% using the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite oxides in an appropriate reaction condition, while the lost lattice x oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite x oxides instead of molecular oxygen to react with methane to synthesis gas in the redox mode.
基金Sponsored by SRF for ROCS, key lab of enhanced heat transfer and energy conservation (MOE)Guangdong provincial natural science foundation (04020126).
文摘Single-phase perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ has been successfully prepared by using citrate-EDTA complexation method at relatively low calcination temperature. The structure and thermal decomposition process of the complex precursor have been investigated by means of differential scanning calorimetry-thermal gravimetric analysis (DSC/TGA), X-ray diffraction (XRD), and Fourier transform infrared spectroscopic (FT-IR) measurements. The precursor decomposed completely and started to form perovskite-type oxide above 420 ℃ according to the differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results. Single-phase perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ obtained has been confirmed from the XRD pattern, and no peak of SrCO3 was found by XRD of the oxides synthesized at a relatively low temperature of 800℃. The reducibility of La0.6Sr0.4Co0.8Fe0.2O3-δ was also characterized by the temperature programmed reduction (TPR) technique. Disk shaped dense La0.6Sr0.4Co0.8Fe0.2O3-δ membrane was prepared by the isostatical pressing method. The oxygen flux rate of dense La0.6Sr0.4Co0.8Fe0.2O3-δ membrane was (2.8-18)× 10^-8 mol/(cm^2.s) in the temperature range of 800-1000 ℃.
文摘The synthesis process for La 1- x Sr x Mn 1- y Co y O 3- δ ( x = 0.2, 0.3; y = 0.2, 0.8, designated as LSMC below) perovskite oxides prepared by solid state reaction was investigated using DSC/TG, XRD, EPMA and particle size analysis methods. It was found that LSMCs were all of single phase and the synthesis process might be divided into three stages: the decomposition of reactants, the formation of LaMn(Co)O 3 based oxides, and the formation of LSMC solid solution. Typical average and the peak value of particle size, and the specific surface area are 14.65?μm, 16.4?μm and 1.38?m 2/mL, respectively, for mixed reactants and are 23.81?μm, 32.11?μm and 0.5?m 2/mL, respectively, for powder synthesized at 1?200?℃ for 8?h in air.
基金Supported by the National Science Fund for Distinguished Young Scholars of China(21225625)the National Natural Science Foundation of China(21176087)the Specialized Research Fund for the Doctoral Program of Higher Education(20110172110013)
文摘Cobalt-free oxides GdxBal-xFeO3-σas(0.01 _〈 x _〈 0.1 ) were achieved by a solid state reaction method. It is found that GdxBal-xFeO3-σas(0.025 _〈 x _〈 0.1) exhibits the cubic perovskite structure. Among GdxBal-xFeO3-σas (0.025 -〈 x -〈 0.1 ), the GdxBal-xFeO3-σas (GBF2.5) membrane shows the outstanding phase structure stability and the highest oxygen permeation, which can reach 1.44 ml. cm- 2. rain- 1 at 950 ℃ under air/He oxygen partial pressure gradient. The GBF2.5 membrane was successfully operated for more than 100 h at 800 ℃ and the oxygen permeation flux through the membrane is 0.62 ml. cm- 2. rain- 1. After 100 h oxygen permeation experiment at 800℃, X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDXS) demonstrate that the GBF2.5 exhibits phase structure stability even at intermediate temoerature.
基金supported by the National Natural Science Foundation of China(No.216060647)the Industry-University-Research Project of Aviation Industry Corporation of China (No.cxy2012HFGD025)
文摘Among the perovskite-type oxides with symmetrical structure applied in oxygen permeable membranes, cubic phase structure is the most favorable for oxygen permeation. In order to stabilize the cubic perovskite structure of BaFeO3-δ material at room temperature, iron was partially substituted by praseodymium. BaFe1-yPryO3-δ powders were synthesized by a solid state reaction method, and sintered samples were prepared from the synthesized BaFe1-yPryO3-δ powders. X-ray diffraction results reveal that the BaFe1-yPryO3-δ samples remain cubic structure at praseodymium substitution amount of y 0.05, 0.075, 0.1. Scanning electron microscope observation indicates that the sintered samples contain only a small amount of enclosed pores and the grain size of BaFe1-yPryO3-δ increase monotonically with the increase of the praseodymium doping amount, praseodymium doping promotes the grain size growth. Tests of electrical conductivity and oxygen permeation flux show that praseodymium doping improves the conduction properties of BaFe1-yPryO3-δ and BaFe0.9Pr0.1O3-δ composition has an electrical conductivity of 6.5 S/era and an oxygen permeation of 1.112 mL/(cm^2.min) at 900 ℃, respectively. High temperature XRD in- vestigation shows that the crystal structure of BaFe0.975Pr0.025O3-δ membrane completely transform to cubic phase at 700℃. The present test results have shown that partially substitution of Fe by praseodymium in BaFeO3 can stabilize the cubic structure and improve the properties.
基金financially supported by the China Scholarship Council,the National Natural Science Foundation of China(21976047,21790373 and 51774104)the Fundamental Research funds for the Central Universities(3072019CF1005)+1 种基金the Scientific Research and Special Foundation Heilongjiang Postdoctoral Science Foundation(LBH-Q15019,LBH-Q15020 and LBH-TZ0411)Ph.D.Student Research and Innovation Fund of the Fundamental Research Funds for the Central Universities(3072019GIP1011)。
文摘Due to the unique structure of perovskite materials,their capacitance can be improved by introducing oxygen vacancy.In this paper,the LaMnO3-δ material containing oxygen vacancy was synthesized by molten salt method in KNO3-NaNO3-NaNO2 melt.The La-Mn-O crystal grows gradually in molten salt with the increase of temperature.It was confirmed that LaMnO3-δ with perovskite structure and incomplete oxygen content were synthesized by molten salt method and presented a three-dimensional shape.LaMnO3-δ stores energy by redox reaction and adsorption of OH-in electrolyte simultaneously.In comparison with the stoichiometric LaMnO3 prepared by the sol-gel method,LaMnO3-δ prepared by molten salt method proffered higher capacitance and better performance.The galvanostatic charge-discharge curve showed specific capacitance of 973.5 F/g under current density of 1 A/g in 6 M KOH.The capacitance of LaMn03-δ was 82.7%under condition of 5 A/g compared with the capacitance at the current of 1A/g,and the specific capacitances of 648.0 and 310.0 F/g were obtained after 2000 and 5000 cycles of galvanostatic charging-discharging,respectively.Molten salt synthesis method is relatively simple and suitable for industrial scale,presenting a promising prospect in the synthesis of perovskite oxide materials.
基金supported by a grant from the Fundamental R&D Program for Core Technology of Materials (No.10051006)funded by the Ministry of Knowledge Economy, Republic of Koreasupported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20113020030050)
文摘LaNi(0.6)Fe(0.4)O(3-δ) (LNF) powders were synthesized by the glycine-nitrate process and LNF-gadolinium-doped ceria (GDC) nanocomposite cathodes for solid oxide fuel cells (SOFCs) were fabricated by infiltration from LNF porous backbones. Electrochemical properties and Cr-poisoning behavior of LNF-GDC cathodes were studied. Single phase perovskite LNF could be obtained at the glycine to nitrate molar ratio of 1:1. The polarization resistance of the LNF-GDC nanocomposite cathode was significantly decreased in comparison with the LNF. This phenomenon was associated with enhanced catalytic activity and enlarged triple-phase boundary (TPB) length by GDC nano particles. In addition, the nanocomposite cathode showed good Cr tolerance under open circuit condition. The LNF-GDC nanocomposite cathodes were expected for use as a potential cathode in intermediate- temperature solid oxide fuel cells (IT-SOFC).
基金The authors gratefully acknowledge the Research Grant Council of Hong Kong for support through the projects 16201820,and 16206019.
文摘BaFeO_(3-δ)-derived perovskites are promising cathodes for intermediate temperature solid oxide fuel cells.The activity of these perovskites depends on the number of oxygen vacancies in their lattice,which can be tuned by cationic substitution.Our first-principle calculations show that Ag is a promising substitute for the Fe site,resulting in a reduced oxygen vacancy formation energy compared with the pristine BaFeO_(3-δ).Ag has limited solubility in perovskites,and its introduction generates an Ag metal secondary phase,which influences the cathode performances.In this work,we investigate the matter,using a Ba0:9La0:1Fe_(1-x)AgxO_(3-δ)series of materials as a case study.Acknowledging the limited solubility of Ag in Ba0:9La0:1Fe_(1-x)AgxO_(3-δ),we aim to distinguish the effects of Ag substitution from those of the Ag secondary phase.We observed that Ag substitution increases the number of oxygen vacancies,confirming our calculations,and facilitates the oxygen incorporation.However,Ag substitution lowers the number of holes,in this way reducing the electronic p-type conductivity.On the other hand,Ag metal positively affects the electronic conductivity and helps the redistribution of the electronic charge at the cathode-electrolyte interface.
基金supported by the National Double First-Class Universities Construction Grant of Sichuan University(2020SCUNG201)the National Natural Science Foundation of China (52072252 and 51902215)+4 种基金Fundamental Research Funds for the Central UniversitiesChina (YJ201886)State Key Laboratory of Polymer Materials EngineeringChina(sklpme2021-JX-01)the Agence Nationale de la Recherche (Labex STORE-EX),France for financial support
文摘Perovskite SrVO_(3) has been investigated as a promising lithium storage anode where the V cation plays the role of the redox center,combining excellent cycle stability and safe operating potential versus Li metal plating,with limited capacity.Here,we demonstrate the possibility to boost the lithium storage properties,by reducing the non-redox active Sr cation content and fine-tuning the O anion vacancies while maintaining a non-stoichiometric Sr_(x)VO_(3-δ) perovskite structure.Theoretical investigations suggest that Sr vacancy can work as favorable Li^(+) storage sites and preferential transport channels for guest Li^(+) ions,contributing to the increased specific capacity and rate performance.In contrast,inducing O anion vacancy in Sr_(x)VO_(3-δ) can improve rate performance while compromising the specific capacity.Our experimental results confirm the enhancement of specific capacities by fine adjusting the Sr and O vacancies,with a maximum capacity of 444 mAh g^(-1) achieved with Sr_(0.63)VO_(3-δ),which is a 37%increase versus stoichiometric SrVO_(3).Although rich defects have been induced,Sr_(x)VO_(3-δ) electrodes maintain a stable perovskite structure during cycling versus a LiFePO_(4) cathode,and the full-cell could achieve more than 6000 discharge/charge cycles with 80%capacity retention.This result highlights the possibility to use the cation defective-based engineering approach to design high-capacity perovskite oxide anode materials.
基金financial support from National Key R&D Program for Young Scientists(2021YFA1501900)National Natural Science Foundation of China(52272257)+4 种基金Material Science and Engineering Discipline Guidance Fund of China University of Mining and Technology(CUMTMS202203)Foundation of State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology(Grant No.SKL2022008)the Jiangsu Provincial Shuangchuang Doctor Program(JSSCBS20211224)Young Elite Scientists Sponsorship Program by(CAST2022QNRC001)the Open Sharing Fund for the Large-scale Instruments(DYGX-2021026)and Equipments of China University of Mining and Technology(CUMT)Analytical for sample characterizations assistance。
文摘Perovskite oxide La_(0.6)Ca_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)(LCFN)has been used in symmetric solid oxide cells(SSOCs)to obtain good electrochemical performance in both fuel cells(SOFCs)and electrolysis cells(SOECs)modes.However,its structural stability still faces challenges and the electrocatalytic activity also needs to be further improved.Herein,tungsten-doped La_(0.6)Ca_(0.4)Fe_(0.7)Ni_(0.2)W_(0.1)0_(3-δ)(LCFNW)perovskite oxide material was synthesized which exhibits good structural stability under H_(2)and superior electrochemical performance as an electrode for SSOCs.In SOFCs mode,the cell achieved the maximum power density of 0.58 W·cm^(-2)with wet H_(2)as fuel at 850℃.In SOECs mode,the current density can reach 1.81 A·cm^(-2)for pure CO_(2)electrolysis at 2 V.Moreover,the SSOCs exhibits outstanding long-term stability in both SOFCs and SOECs modes,proving that doping W in perovskite oxide is an effective strategy to enhance the catalytic activity and stability of the electrode.The LCFNW material developed in this work shows promising prospect as an electrode candidate for SSOCs.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant No. 59789201), the National Advanced Materials Committee of China (Grant No. 715-006-0122) and the Ministry of Science and Technology, China (Grant No. G1
文摘La0.15Sr0.85Ga0.3Fe0.7O3-δ (LSGFO) and La0.15Sr0.85Co0.3Fe0.7O3-δ (LSCFO) mixed oxygenion and electron conducting oxides were synthesized by using a combined EDTA and citrate complexing method, and the corresponding dense membranes were fabricated. The properties of the oxide powders and membranes were characterized with combined SEM, XRD, H2-TPR, O2-TPD techniques, mechanical strength and oxygen permeation measurement. The results showed that LSGFO had much higher thermochemical stability than LSCFO due to the higher valence stability of Ga3+. After the temperature-programmed reduction by 5% H2 in Ar from 20°C to 1020°C, the basic perovskite structure of LSGFO was successfully preserved. LSGFO also favors the oxygen vacancy formation better than LSCFO. Oxygen permeation measurement demonstrated that LSGFO had higher oxygen permeation flux than LSCFO, but they had similar activation energy for oxygen transportation, with a value of 110 and 117 kJ · mol-1, respectively. The difference in oxygen permeation fluxes was correlated with the difference in oxygen vacancy concentrations for the two materials.
基金financially supported by the National Natural Science Foundation of China (Nos.51174133,51274139 and 51225401)the Science and Technology Commission of Shanghai Municipality (No.11ZR1412900)
文摘The permeability and stability of Sm_(0.7)Sr_(0.3)CoO_(3-δ)(SSCO) regarding the special requirements for carbon capture and storage(CCS) application were investigated.Pure CO_ was used as the sweep gas at 900 °C,leading to that the oxygen permeation flux decreases by about 34 %.Several cycles of changing the sweep gas between helium and CO_2 indicate the good reversibility of this degradation.Both carbonate formation and adsorption of CO_2 on the membrane surface are responsible for the degradation of the membrane performance.The better CO_2 resistance results from the substitution of Sm for Sr due to the higher acidity of Sm_2O_3(1.278) than that of Sr O(0.978) and a discontinuous layer of carbonate.