Ba0.5Sr0.5Co0.5Fe0.2O3-σ(BSCF), a new cathode material for solid oxide fuel cell (SOFC), was synthesized by polyacrylicacid (PAA) method. The lattice structures of samples calcined at different temperatures were char...Ba0.5Sr0.5Co0.5Fe0.2O3-σ(BSCF), a new cathode material for solid oxide fuel cell (SOFC), was synthesized by polyacrylicacid (PAA) method. The lattice structures of samples calcined at different temperatures were characterized by XRD, Shrinkage, porosity and pore size of the porous BSCF as a function of sintering temperature were investigated. It was found that the cubic perovskite structure could be formed after calcination at 800 ℃ for 2 h, but not well crystallized as seen from some unknown phases, and the pure cubic perovskite structure was formed after calcination at 1150 ℃ for 2 h. The panicle size of BSCF was less than 1-2 μm. The shrinkage of the porous BSCF increased with sintering temperature, but the opposite was true for the porosity. After sintering at 1100 ℃ for 4 h, the porous BSCF was still in an appropriate structure, with porosity of 29% and electrical conductivity above 400 S·cm^-1.展开更多
In this work, microwave dielectric properties of A-site substitution by La 3+ in (Pb_ 0.45Ca_ 0.55)(Fe_ 0.5Nb_ 0.5)O_3 system were investigated. Microwave dielectric properties of A-site charge unbalance substitution ...In this work, microwave dielectric properties of A-site substitution by La 3+ in (Pb_ 0.45Ca_ 0.55)(Fe_ 0.5Nb_ 0.5)O_3 system were investigated. Microwave dielectric properties of A-site charge unbalance substitution of [(Pb_ 0.45Ca_ 0.55)_ 1-xLa_x](Fe_ 0.5Nb_ 0.5)O 3+ (P45CLFN) were improved because the solid solution of small amount of surplus La 3+ with (Pb,Ca) 2+ could eliminate oxygen vacancies, and the formation of secondary phase(pyrochlore) was also caused by surplus La 3+. The decreasing of dielectric constant with the increase of La 3+ content is due to the formation of pyrochlore. The grain size is changed slightly and Q_f values(7000～7300 GHz) are almost unchanged at x=0.02～0.10, but the temperature coefficient of resonant frequency (TCF) are increased and changed from negative to positive. TCF is zero at x=0075 with Q_f=7267 GHz and K=89. TCF of all specimens are within ±5×10 -6 ℃ -1.展开更多
Promoting the oxygen reduction reaction(ORR)is critical for commercialization of intermediate-temperature solid oxide fuel cells(IT-SOFCs),where Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)−δ(SFM)is a promising cathode by working as ...Promoting the oxygen reduction reaction(ORR)is critical for commercialization of intermediate-temperature solid oxide fuel cells(IT-SOFCs),where Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)−δ(SFM)is a promising cathode by working as a mixed ionic and electronic conductor.In this work,doping of In^(3+)greatly increases the oxygen vacancy concentration and the content of adsorbed oxygen species in Sr_(2)Fe_(1.5)Mo_(0.5−x)InxO_(6−δ)(SFMInx),and thus effectively promotes the ORR performance.As a typical example,SFMIn_(0.1)reduces the polarization resistance(R_(p))from 0.089 to 0.046Ω∙cm^(2)at 800°C,which is superior to those doped with other metal elements.In addition,SFMIn0.1 increases the peak power density from 0.92 to 1.47 W∙cm^(−2)at 800°C with humidified H_(2)as the fuel,indicating that In3+doping at the Mo site can effectively improve the performance of SOFC cathode material.展开更多
A pure phase BaCo_(0.5)Fe_(0.5)O_(3–δ)(BCF),which cannot be obtained before,is successfully prepared in this study by using the calcination method with a rapid cooling procedure.The successful preparation of BCF all...A pure phase BaCo_(0.5)Fe_(0.5)O_(3–δ)(BCF),which cannot be obtained before,is successfully prepared in this study by using the calcination method with a rapid cooling procedure.The successful preparation of BCF allows the evaluation of this material as a cathode for proton-conducting solid oxide fuel cells(H-SOFCs)for the first time.An H-SOFC using the BCF cathode achieves an encouraging fuel cell performance of 2012 mW·cm–2 at 700,two℃-fold higher than that of a similar cell using the classical high-performance Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3–δ)(BSCF)cathode.First-principles calculations reveal the mechanism for the performance enhancement,indicating that the new BCF cathode significantly lowers the energy barriers in the oxygen reduction reaction(ORR)compared with the BSCF cathode.Therefore,improved cathode performance and fuel cell output are obtained for the BCF cell.The fuel cell using the BCF cathode also shows excellent long-term stability that can work stably for nearly 900 h without noticeable degradations.The fuel cell performance and long-term stability of the current BCF cell are superior to most of the H-SOFCs reported in previous reports,suggesting that BCF is a promising cathode for H-SOFCs.展开更多
Electrochemical conversion of CO_(2)to CO is an economically feasible method for mitigating greenhouse gas emissions.Among various electrochemical approaches,solid oxide electrolysis cells(SOECs)show high potential fo...Electrochemical conversion of CO_(2)to CO is an economically feasible method for mitigating greenhouse gas emissions.Among various electrochemical approaches,solid oxide electrolysis cells(SOECs)show high potential for CO_(2)reduction reaction(CO_(2)-RR)due to their ability to operate at high temperatures,resulting in fast reaction kinetics and increased efficiency.Considering their main energy loss is still associated with the large overpotential at the fuel electrode,the development of the highly efficient and durable cathode for SOECs has been extensively searched after.Here,we propose an A-site doping strategy to enhance the properties of Sr_(2)Fe_(1.5)Mo_(0.5)O_(6−δ)(SFM),which improve its performance as a cathode in SOECs for CO_(2)-RR,demonstrating favorable activity and durability.The structural and physiochemical characterizations,together with DFT calculations,show that the partial replacement of Sr by Bi in the SFM double perovskite not only improves CO_(2) adsorption capability at the catalyst surface but also enhances oxygen ionic conduction inside the bulk oxide,resulting in enhanced CO_(2)electrocatalysis performance in SOECs.Specifically,a La_(0.8)Sr_(0.2)Ga_(0.8)Mg_(0.2)O_(3−δ) (LSGM)electrolyte-supported single cell with the new Bi-doped SFM cathode demonstrates a large current density of 1620 mA cm^(−2) at a cell potential of 1.6 V at 850°C with good operational stability up to 200 h.Bi-doped SFM thus represents a highly promising cathode for ceramic CO_(2)electrolyzers and could accelerate our transition towards a carbon-neutral society.展开更多
A new Eu-based microwave dielectric ceramic,Eu(MgTi)O(EMT for short), was prepared through conventional solid-state reactions. The EMT ceramics were well densified at 1425 ℃ and exhibit good microwave dielectric prop...A new Eu-based microwave dielectric ceramic,Eu(MgTi)O(EMT for short), was prepared through conventional solid-state reactions. The EMT ceramics were well densified at 1425 ℃ and exhibit good microwave dielectric properties with permittivity of 23.92, high quality factor(Q*f) of 66,957 GHz at 8.93 GHz and relatively low-temperature coefficient of resonant frequency of-20.3 10/K. Additionally, the variations of dielectric constants among Ln(MgTi)O(Ln represents rare earth elements, LMT) compounds were analyzed. Ionic radii of Ln, associated with the tolerance factors of the perovskite structure of LMT, were investigated to be the key factor to influence the permittivity. These results indicate that EMT ceramics might be one of the promising candidates as microwave resonators.展开更多
This paper describes a detailed analysis of the dependence of Raman scattering intensity on the polarization of the incident and inelastically scattered light in PbSc_(0.5)Nb_(0.5)O_(3)(PSN)single crystals and epitaxi...This paper describes a detailed analysis of the dependence of Raman scattering intensity on the polarization of the incident and inelastically scattered light in PbSc_(0.5)Nb_(0.5)O_(3)(PSN)single crystals and epitaxially compressed thin films grown on(100)-oriented MgO substrates.It is found that there are significant differences between the properties of the crystals and films,and that these differences can be attributed to the anticipated structural differences between these two forms of the same material.In particular,the scattering characteristics of the oxygen octahedra breathing mode near 810 cm^(-1) indicate a ferroelectric state for the crystals and a relaxor state for the films,which is consistent with the dielectric behaviors of these materials.展开更多
文摘Ba0.5Sr0.5Co0.5Fe0.2O3-σ(BSCF), a new cathode material for solid oxide fuel cell (SOFC), was synthesized by polyacrylicacid (PAA) method. The lattice structures of samples calcined at different temperatures were characterized by XRD, Shrinkage, porosity and pore size of the porous BSCF as a function of sintering temperature were investigated. It was found that the cubic perovskite structure could be formed after calcination at 800 ℃ for 2 h, but not well crystallized as seen from some unknown phases, and the pure cubic perovskite structure was formed after calcination at 1150 ℃ for 2 h. The panicle size of BSCF was less than 1-2 μm. The shrinkage of the porous BSCF increased with sintering temperature, but the opposite was true for the porosity. After sintering at 1100 ℃ for 4 h, the porous BSCF was still in an appropriate structure, with porosity of 29% and electrical conductivity above 400 S·cm^-1.
文摘In this work, microwave dielectric properties of A-site substitution by La 3+ in (Pb_ 0.45Ca_ 0.55)(Fe_ 0.5Nb_ 0.5)O_3 system were investigated. Microwave dielectric properties of A-site charge unbalance substitution of [(Pb_ 0.45Ca_ 0.55)_ 1-xLa_x](Fe_ 0.5Nb_ 0.5)O 3+ (P45CLFN) were improved because the solid solution of small amount of surplus La 3+ with (Pb,Ca) 2+ could eliminate oxygen vacancies, and the formation of secondary phase(pyrochlore) was also caused by surplus La 3+. The decreasing of dielectric constant with the increase of La 3+ content is due to the formation of pyrochlore. The grain size is changed slightly and Q_f values(7000～7300 GHz) are almost unchanged at x=0.02～0.10, but the temperature coefficient of resonant frequency (TCF) are increased and changed from negative to positive. TCF is zero at x=0075 with Q_f=7267 GHz and K=89. TCF of all specimens are within ±5×10 -6 ℃ -1.
基金acknowledge the Autonomous Region Key Research Project(No.2022D02D31)the Graduate Education Innovation Project(No.XJ2022G046)。
文摘Promoting the oxygen reduction reaction(ORR)is critical for commercialization of intermediate-temperature solid oxide fuel cells(IT-SOFCs),where Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)−δ(SFM)is a promising cathode by working as a mixed ionic and electronic conductor.In this work,doping of In^(3+)greatly increases the oxygen vacancy concentration and the content of adsorbed oxygen species in Sr_(2)Fe_(1.5)Mo_(0.5−x)InxO_(6−δ)(SFMInx),and thus effectively promotes the ORR performance.As a typical example,SFMIn_(0.1)reduces the polarization resistance(R_(p))from 0.089 to 0.046Ω∙cm^(2)at 800°C,which is superior to those doped with other metal elements.In addition,SFMIn0.1 increases the peak power density from 0.92 to 1.47 W∙cm^(−2)at 800°C with humidified H_(2)as the fuel,indicating that In3+doping at the Mo site can effectively improve the performance of SOFC cathode material.
基金supported by the National Natural Science Foundation of China(51972183)the Hundred Youth Talents Program of Hunan,and the Startup Funding for Talents at the University of South China.
基金supported by the National Natural Science Foundation of China(Grant Nos.52272216 and 51972183)the Hundred Youth Talents Program of Hunan,and the Startup Funding for Talents at University of South China.
文摘A pure phase BaCo_(0.5)Fe_(0.5)O_(3–δ)(BCF),which cannot be obtained before,is successfully prepared in this study by using the calcination method with a rapid cooling procedure.The successful preparation of BCF allows the evaluation of this material as a cathode for proton-conducting solid oxide fuel cells(H-SOFCs)for the first time.An H-SOFC using the BCF cathode achieves an encouraging fuel cell performance of 2012 mW·cm–2 at 700,two℃-fold higher than that of a similar cell using the classical high-performance Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3–δ)(BSCF)cathode.First-principles calculations reveal the mechanism for the performance enhancement,indicating that the new BCF cathode significantly lowers the energy barriers in the oxygen reduction reaction(ORR)compared with the BSCF cathode.Therefore,improved cathode performance and fuel cell output are obtained for the BCF cell.The fuel cell using the BCF cathode also shows excellent long-term stability that can work stably for nearly 900 h without noticeable degradations.The fuel cell performance and long-term stability of the current BCF cell are superior to most of the H-SOFCs reported in previous reports,suggesting that BCF is a promising cathode for H-SOFCs.
基金financially supported by the State Key Laboratory of Clean Energy Utilization(Open Fund Project No.ZJUCEU2021001)Natural Science Foundation of Jiangsu Province(No.BK20221312).
文摘Electrochemical conversion of CO_(2)to CO is an economically feasible method for mitigating greenhouse gas emissions.Among various electrochemical approaches,solid oxide electrolysis cells(SOECs)show high potential for CO_(2)reduction reaction(CO_(2)-RR)due to their ability to operate at high temperatures,resulting in fast reaction kinetics and increased efficiency.Considering their main energy loss is still associated with the large overpotential at the fuel electrode,the development of the highly efficient and durable cathode for SOECs has been extensively searched after.Here,we propose an A-site doping strategy to enhance the properties of Sr_(2)Fe_(1.5)Mo_(0.5)O_(6−δ)(SFM),which improve its performance as a cathode in SOECs for CO_(2)-RR,demonstrating favorable activity and durability.The structural and physiochemical characterizations,together with DFT calculations,show that the partial replacement of Sr by Bi in the SFM double perovskite not only improves CO_(2) adsorption capability at the catalyst surface but also enhances oxygen ionic conduction inside the bulk oxide,resulting in enhanced CO_(2)electrocatalysis performance in SOECs.Specifically,a La_(0.8)Sr_(0.2)Ga_(0.8)Mg_(0.2)O_(3−δ) (LSGM)electrolyte-supported single cell with the new Bi-doped SFM cathode demonstrates a large current density of 1620 mA cm^(−2) at a cell potential of 1.6 V at 850°C with good operational stability up to 200 h.Bi-doped SFM thus represents a highly promising cathode for ceramic CO_(2)electrolyzers and could accelerate our transition towards a carbon-neutral society.
基金financially supported by the National Basic Research Program of China (No. 2015CB654902)the National Natural Science Foundation of China (Nos. 51390471 and 51527803)the National Key Research and Development Program (No. 2016YFB0700402)
文摘A new Eu-based microwave dielectric ceramic,Eu(MgTi)O(EMT for short), was prepared through conventional solid-state reactions. The EMT ceramics were well densified at 1425 ℃ and exhibit good microwave dielectric properties with permittivity of 23.92, high quality factor(Q*f) of 66,957 GHz at 8.93 GHz and relatively low-temperature coefficient of resonant frequency of-20.3 10/K. Additionally, the variations of dielectric constants among Ln(MgTi)O(Ln represents rare earth elements, LMT) compounds were analyzed. Ionic radii of Ln, associated with the tolerance factors of the perovskite structure of LMT, were investigated to be the key factor to influence the permittivity. These results indicate that EMT ceramics might be one of the promising candidates as microwave resonators.
基金supported by the Czech Science Foundation(Projects CSF 15-04121S and 15-15123S)the United Stated Office of Naval Research(Grant No.N00014-12-1-1045)the Natural Science&Engineering Research Council of Canada(NSERC).
文摘This paper describes a detailed analysis of the dependence of Raman scattering intensity on the polarization of the incident and inelastically scattered light in PbSc_(0.5)Nb_(0.5)O_(3)(PSN)single crystals and epitaxially compressed thin films grown on(100)-oriented MgO substrates.It is found that there are significant differences between the properties of the crystals and films,and that these differences can be attributed to the anticipated structural differences between these two forms of the same material.In particular,the scattering characteristics of the oxygen octahedra breathing mode near 810 cm^(-1) indicate a ferroelectric state for the crystals and a relaxor state for the films,which is consistent with the dielectric behaviors of these materials.
