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
通过甘氨酸硝酸盐法（GNP）合成了钙钛矿型Ba0.5Sr0.5Co0.8Fe0.2O3-δ（BSCF）复合氧化物粉体。经压制、烧结后,得到了BSCF烧结体试样,还通过硝酸溶液浸蚀处理对烧结体试样进行了表面浸蚀处理。采用X射线衍射仪（XRD）对煅烧后的粉体进...通过甘氨酸硝酸盐法（GNP）合成了钙钛矿型Ba0.5Sr0.5Co0.8Fe0.2O3-δ（BSCF）复合氧化物粉体。经压制、烧结后,得到了BSCF烧结体试样,还通过硝酸溶液浸蚀处理对烧结体试样进行了表面浸蚀处理。采用X射线衍射仪（XRD）对煅烧后的粉体进行了相成分分析;采用扫描电子显微镜（SEM）及能谱仪（EDS）对烧结体和表面浸蚀后烧结体样品的微观组织和成分进行了表征;对烧结体的致密度、电导率进行了测试分析,并在自制的氧渗透装置上测定了BSCF钙钛矿膜的透氧量,分析了温度和不同氧分压差等对膜透氧性能的影响。实验结果表明,甘氨酸-硝酸盐法所制备的前驱体粉末在900℃煅烧3 h后可获得具有单一钙钛矿结构的BSCF粉体,1100℃煅烧的BSCF烧结体的电导率在600℃时最大达到38.15 S·cm-1。其透氧量随着温度和氧分压差的升高而增大,且硝酸表面浸蚀处理后,BSCF膜片的透氧性能有明显提高,透氧速率提高1.6~4.5倍。850℃,20%O2-80%N2混合气体/He条件下,浸蚀后的透氧膜片的透氧量达到2.36 m L/cm2·min,而未浸蚀透氧膜片的透氧量仅为1.36 m L/cm2·min。展开更多
The nano ceramic Ba0.5Sr0.5Co0.2Fe0.8O3 (BSCF) powders have been synthesized by Sol-Gel process using nitrate based chemicals for SOFC applications since these powders are considered to be more promising cathode mater...The nano ceramic Ba0.5Sr0.5Co0.2Fe0.8O3 (BSCF) powders have been synthesized by Sol-Gel process using nitrate based chemicals for SOFC applications since these powders are considered to be more promising cathode materials for SOFC. Glycine was used as a chelant agent and ethylene glycol as a dispersant. The powders were calcined at 850℃/3 hr in the air using Thermolyne 47,900 furnace. These powders were characterized by employing SEM/EDS, XRD and TGA/DTA techniques. The SEM images BSCF powder indicate the presence of highly porous spherical particles with nano sizes. The XRD results shows the formation of BSCF perovskite phase at the calcination temperature of 850℃. From XRD line broadening technique, the average crystllite size of the BSCF powders were found to be around 9.15 - 11.83 nm and 13.63 - 17.47 nm for as prepared and after calcination at 850℃ respectively. The TGA plot shows that there is no weight loss after the temperature around 450℃ indicating completion of combustion.展开更多
Ba0.5Sr0.5Co0.8Fe0.2O3-delta and Ba0.5Sr0.5Co0.8Ti0.2O3-delta oxides were synthesized by a combined EDTA-citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied ...Ba0.5Sr0.5Co0.8Fe0.2O3-delta and Ba0.5Sr0.5Co0.8Ti0.2O3-delta oxides were synthesized by a combined EDTA-citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied during the reaction of methane oxidation. The pre-treatment with methane has different effect on the catalytic activities of both the oxides. The methane pre-treatment has not resulted in the change of the catalytic activity of BSCFO owing to its excellent reversibility of the perovskite structure resulting from the excellent synergistic interaction between Co and Fe in the oxide. However, the substitution with Ti on Fe-site in the lattice makes the methane pre-treatment have an obvious influence on the activity of the formed BSCTO oxide.展开更多
A novel pulse 18O-16O isotopic exchange (PIE) technique for measurement of the rate of oxygen surface exchange of oxide ion conductors was presented. The technique employs a continuous flow packed-bed micro-reactor lo...A novel pulse 18O-16O isotopic exchange (PIE) technique for measurement of the rate of oxygen surface exchange of oxide ion conductors was presented. The technique employs a continuous flow packed-bed micro-reactor loaded with the oxide powder. The isothermal response to an 18O-enriched pulse passing through the reactor, thereby maintaining chemical equilibrium, is measured by on-line mass spectrometry. Evaluation of the apparent exchange rate follows from the uptake of 18O by the oxide at given reactor residence time and surface area available for exchange. The developed PIE technique is rapid, simple and highly suitable for screening and systematic studies. No rapid heating/quenching steps are required to facilitate 18O tracer anneal or analysis, as in other commonly used techniques based upon oxygen isotopic exchange. Moreover, the relative distribution of the oxygen isotopologues 18O2, 16O18O, and 16O2 in the effluent pulse provides insight into the mechanism of the oxygen exchange reaction. The PIE technique has been demonstrated by measuring the exchange rate of selected oxides with enhanced oxide ionic conductivity in the range of 350?900 oC. Analysis of the experimental data in terms of a model with two consecutive, lumped steps for the isotopic exchange reaction shows that for mixed conductors Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) and La2NiO4+δ the reaction is limited by the apparent rate of dissociative adsorption of O2 molecules at the oxide surface. For yttria-stabilized zirconia (YSZ), a change-over takes place, from rate-limitations by oxygen incorporation below ∽800 oC to rate-limitations by O2 dissociative adsorption above this temperature. Good agreement is obtained with exchange rates reported for these materials in literature.展开更多
A composite paste electrode based on Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)—initially synthesized by solgel method—and multiwall carbon nanotube (MWCNT) as a cathode in fuel cells is developed. The composite pastes are pr...A composite paste electrode based on Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)—initially synthesized by solgel method—and multiwall carbon nanotube (MWCNT) as a cathode in fuel cells is developed. The composite pastes are prepared by the direct mixing of BSCF:MWCNT at 90:10, 80:20 and 70:30 (% w/W). These electrodes are then characterized by the x-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherm, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The XRD and SEM confirm the inclusion and the uniform dispersal of the MWCNT within BSCF, respectively. The nitrogen adsorption isotherm study shows that the porosity of the composite paste electrode has been improved by two-fold from the BSCF electrode. The EIS and CV demonstrate that the higher ratios of MWCNT in the composites are critical in improving the electronic conductivity as well as the kinetics. It is also noticeable that the electrode has increased the catalysis of oxygen in 0.1 M KOH (pH 12.0). Cyclic voltammetric studies on the oxygen reduction reaction (ORR) suggest that the incorporation of MWCNT is vital in improving the electrode (cathode) properties of a fuel cell.展开更多
Ba\-\{0.5\}Sr\-\{0.5\}Co\-\{0.8\}Fe\-\{0.2\}O\-\{3-\%δ\%\} and Ba\-\{0.5\}Sr\-\{0.5\}Co\-\{0.8\}Ti\-\{0.2\}O\-\{3-\%δ\%\} oxides were synthesized by a combined EDTA\|citrate complexing method. The catalytic behavior...Ba\-\{0.5\}Sr\-\{0.5\}Co\-\{0.8\}Fe\-\{0.2\}O\-\{3-\%δ\%\} and Ba\-\{0.5\}Sr\-\{0.5\}Co\-\{0.8\}Ti\-\{0.2\}O\-\{3-\%δ\%\} oxides were synthesized by a combined EDTA\|citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied during the reaction of methane oxidation. The pre\|treatment with methane has different effect on the catalytic activities of both the oxides. The methane pre\|treatment has not resulted in the change of the catalytic activity of BSCFO owing to its excellent reversibility of the perovskite structure resulting from the excellent synergistic interaction between Co and Fe in the oxide. However, the substitution with Ti on Fe\|site in the lattice makes the methane pre\|treatment have an obvious influence on the activity of the formed BSCTO oxide.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.
文摘通过甘氨酸硝酸盐法（GNP）合成了钙钛矿型Ba0.5Sr0.5Co0.8Fe0.2O3-δ（BSCF）复合氧化物粉体。经压制、烧结后,得到了BSCF烧结体试样,还通过硝酸溶液浸蚀处理对烧结体试样进行了表面浸蚀处理。采用X射线衍射仪（XRD）对煅烧后的粉体进行了相成分分析;采用扫描电子显微镜（SEM）及能谱仪（EDS）对烧结体和表面浸蚀后烧结体样品的微观组织和成分进行了表征;对烧结体的致密度、电导率进行了测试分析,并在自制的氧渗透装置上测定了BSCF钙钛矿膜的透氧量,分析了温度和不同氧分压差等对膜透氧性能的影响。实验结果表明,甘氨酸-硝酸盐法所制备的前驱体粉末在900℃煅烧3 h后可获得具有单一钙钛矿结构的BSCF粉体,1100℃煅烧的BSCF烧结体的电导率在600℃时最大达到38.15 S·cm-1。其透氧量随着温度和氧分压差的升高而增大,且硝酸表面浸蚀处理后,BSCF膜片的透氧性能有明显提高,透氧速率提高1.6~4.5倍。850℃,20%O2-80%N2混合气体/He条件下,浸蚀后的透氧膜片的透氧量达到2.36 m L/cm2·min,而未浸蚀透氧膜片的透氧量仅为1.36 m L/cm2·min。
文摘The nano ceramic Ba0.5Sr0.5Co0.2Fe0.8O3 (BSCF) powders have been synthesized by Sol-Gel process using nitrate based chemicals for SOFC applications since these powders are considered to be more promising cathode materials for SOFC. Glycine was used as a chelant agent and ethylene glycol as a dispersant. The powders were calcined at 850℃/3 hr in the air using Thermolyne 47,900 furnace. These powders were characterized by employing SEM/EDS, XRD and TGA/DTA techniques. The SEM images BSCF powder indicate the presence of highly porous spherical particles with nano sizes. The XRD results shows the formation of BSCF perovskite phase at the calcination temperature of 850℃. From XRD line broadening technique, the average crystllite size of the BSCF powders were found to be around 9.15 - 11.83 nm and 13.63 - 17.47 nm for as prepared and after calcination at 850℃ respectively. The TGA plot shows that there is no weight loss after the temperature around 450℃ indicating completion of combustion.
文摘Ba0.5Sr0.5Co0.8Fe0.2O3-delta and Ba0.5Sr0.5Co0.8Ti0.2O3-delta oxides were synthesized by a combined EDTA-citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied during the reaction of methane oxidation. The pre-treatment with methane has different effect on the catalytic activities of both the oxides. The methane pre-treatment has not resulted in the change of the catalytic activity of BSCFO owing to its excellent reversibility of the perovskite structure resulting from the excellent synergistic interaction between Co and Fe in the oxide. However, the substitution with Ti on Fe-site in the lattice makes the methane pre-treatment have an obvious influence on the activity of the formed BSCTO oxide.
文摘A novel pulse 18O-16O isotopic exchange (PIE) technique for measurement of the rate of oxygen surface exchange of oxide ion conductors was presented. The technique employs a continuous flow packed-bed micro-reactor loaded with the oxide powder. The isothermal response to an 18O-enriched pulse passing through the reactor, thereby maintaining chemical equilibrium, is measured by on-line mass spectrometry. Evaluation of the apparent exchange rate follows from the uptake of 18O by the oxide at given reactor residence time and surface area available for exchange. The developed PIE technique is rapid, simple and highly suitable for screening and systematic studies. No rapid heating/quenching steps are required to facilitate 18O tracer anneal or analysis, as in other commonly used techniques based upon oxygen isotopic exchange. Moreover, the relative distribution of the oxygen isotopologues 18O2, 16O18O, and 16O2 in the effluent pulse provides insight into the mechanism of the oxygen exchange reaction. The PIE technique has been demonstrated by measuring the exchange rate of selected oxides with enhanced oxide ionic conductivity in the range of 350?900 oC. Analysis of the experimental data in terms of a model with two consecutive, lumped steps for the isotopic exchange reaction shows that for mixed conductors Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) and La2NiO4+δ the reaction is limited by the apparent rate of dissociative adsorption of O2 molecules at the oxide surface. For yttria-stabilized zirconia (YSZ), a change-over takes place, from rate-limitations by oxygen incorporation below ∽800 oC to rate-limitations by O2 dissociative adsorption above this temperature. Good agreement is obtained with exchange rates reported for these materials in literature.
文摘A composite paste electrode based on Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)—initially synthesized by solgel method—and multiwall carbon nanotube (MWCNT) as a cathode in fuel cells is developed. The composite pastes are prepared by the direct mixing of BSCF:MWCNT at 90:10, 80:20 and 70:30 (% w/W). These electrodes are then characterized by the x-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherm, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The XRD and SEM confirm the inclusion and the uniform dispersal of the MWCNT within BSCF, respectively. The nitrogen adsorption isotherm study shows that the porosity of the composite paste electrode has been improved by two-fold from the BSCF electrode. The EIS and CV demonstrate that the higher ratios of MWCNT in the composites are critical in improving the electronic conductivity as well as the kinetics. It is also noticeable that the electrode has increased the catalysis of oxygen in 0.1 M KOH (pH 12.0). Cyclic voltammetric studies on the oxygen reduction reaction (ORR) suggest that the incorporation of MWCNT is vital in improving the electrode (cathode) properties of a fuel cell.
文摘Ba\-\{0.5\}Sr\-\{0.5\}Co\-\{0.8\}Fe\-\{0.2\}O\-\{3-\%δ\%\} and Ba\-\{0.5\}Sr\-\{0.5\}Co\-\{0.8\}Ti\-\{0.2\}O\-\{3-\%δ\%\} oxides were synthesized by a combined EDTA\|citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied during the reaction of methane oxidation. The pre\|treatment with methane has different effect on the catalytic activities of both the oxides. The methane pre\|treatment has not resulted in the change of the catalytic activity of BSCFO owing to its excellent reversibility of the perovskite structure resulting from the excellent synergistic interaction between Co and Fe in the oxide. However, the substitution with Ti on Fe\|site in the lattice makes the methane pre\|treatment have an obvious influence on the activity of the formed BSCTO oxide.
