• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.148-155
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• 2015

Electrospun $LaCoO_3$ perovskite nanofibers were produced for the air electrode in Zn-air rechargeable batteries using electrospinning technique with sequential calcination. The final calcination temperature was varied from 500 to $800^{\circ}C$ in order to determine its effect on the physical and electrochemical properties of the prepared $LaCoO_3$ perovskite nanofibers. The surface area of the electrospun $LaCoO_3$ perovskite nanofibers were observed to decrease with increasing final calcination temperature. Electrospun $LaCoO_3$ perovskite nanofibers calcined with final calcination temperature of $700^{\circ}C$ had the best electrocatalytic activity among the prepared perovskite nanofibers.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.1
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• pp.41-52
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• 2021

NiO and Co3O4-doped porous La(CoNi)O3 perovskite oxides were prepared from excess Ni addition by a hydrothermal method using porous silica template, and characterized as bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for Zn-air rechargeable batteries in alkaline solution. Excess Ni induced to form NiO and Co3O4 in La(CoNi)O3 particles. The NiO and Co3O4-doped porous La(CoNi)O3 showed high specific surface area, up to nine times of conventionally synthesized perovskite oxide, and abundant pore volume with similar structure. Extra added Ni was partially substituted for Co as B site of ABO3 perovskite structure and formed to NiO and Co3O4 which was highly dispersed in particles. Excess Ni in La(CoNi)O3 catalysts increased OER performance (259 mA/㎠ at 2.4 V) in alkaline solution, although the activities (211 mA/㎠ at 0.5 V) for ORR were not changed with the content of excess Ni. La(CoNi)O3 with excess Ni showed very stable cyclability and low capacity fading rate (0.38 & 0.07 ㎶/hour for ORR & OER) until 300 hours (~70 cycles) but more excess content of Ni in La(CoNi)O3 gave negative effect to cyclability.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.718-722
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• 2017

We have investigated the photocatalytic activity for the decomposition of methyl orange on the pure $LaCoO_3$ and metal ion doped $LaCoO_3$ perovskite-typeoxides prepared using microwave process. In the case of pure $LaCoO_3$ and cesium ion doped $LaCoO_3$ catalysts, the formation of the perovskite crystalline phase was confirmed regardless of the preparation method. From the results of UV-Vis DRS, the pure $LaCoO_3$ and cesium ion doped $LaCoO_3$ catalysts have the similar absorption spectrum up to visible region. The chemisorbed oxygen plays an important role on the photocatalytic decomposition of methyl orange and the higher the contents of chemisorbed oxygen, the better performance of photocatalyst.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.1
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• pp.32-39
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• 2007

CO oxidation and selective CO oxidation of $La_xCe_{1-x}Co_yCu_{1-y}O_{3-{\alpha}}$ perovskite(x=1, 0.9, 0.7. 0.5; y=1, 0.9, 0.7, 0.5) were investigated. For CO oxidation, catalytic activities were studied according to different preparation conditions such as pH and calcination temperature. The influence of the change of the $O_2$ concentration for selective CO oxidation was studied, too. The substitution of Ce for La improved the catalytic activity for CO oxidation and selective CO oxidation and best activity was observed for $La_{0.7}Ce_{0.3}CoO_3$ prepared at pH 11 and calcined at $600^{\circ}C$. The temperature of 90% CO conversion for CO oxidation using $La_{0.7}Ce_{0.3}CoO_3$ was $230^{\circ}C$. In contrast to the enhancement effect by Ce substitution, the partial substitution of Cu for Co in $LaCo_yCu_{1-y}O_{3-{\alpha}}$ decreased catalytic activities for CO oxidation reaction compared to that using $LaCoO_3$. For selective CO oxidation, the best CO conversion was 66% at $230^{\circ}C$ for $La_{0.7}Ce_{0.3}CoO_3$. The CO conversion of $La_{0.7}Ce_{0.3}CoO_3$ was greatly increased from 66% to 91% as increasing $O_2$ concentration from 1% to 2%.

• Bulletin of the Korean Chemical Society
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• v.9 no.5
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• pp.283-288
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• 1988

The titled properties on reduction of the perovskite $LaBO_3$ (B = Fe, Co, Ni) have been investigated by means of temperature-programmed reduction, isothermal reduction and X-ray diffraction methods. Nominal composition of $LaFeO_{3.18},\;LaCoO_{3.00}\;and\;LaNiO_{2.92}$ are determined. Reduction reaction of these mixed oxides differed according to B-site transition metal and thermal stability on reduction decreased as following order: $LaFeO_{3.18}$ > $LaCoO_{3.00}$ > $LaNiO_{2.92}$. From the results of isothermal reaction, kinetics on reduction of the perovskite has been discussed in detail.

• Journal of the Korean Society of Safety
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• v.3 no.1
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• pp.7-13
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• 1988

The oxides in perovskite type, $LaMO_3$ (M=Ni, Cr, Fe, Co), compared with gas sensors which have been used, were synthesised and then examined sensor response comparatively in order to make a thick film gas sensor having a good gas selectivity, durability and simple manufacturing. The oxides in perovskite type, $LaFe_{1-x}O_3$ (x=0.2, 0.4, 0.6, 0.8), which a part of Fe was replaced with Co, were examined with regard to their electric resistance with variable temperature and sensor response for carbon monoxide gas.

• Journal of the Korean Chemical Society
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• v.38 no.4
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• pp.276-282
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• 1994

Perovskite-type mixed oxides LaBO$_3$(B = Mn, Fe, Co) were prepared by citrate sol-gel method in $air(850^{\circ}C$, 24h). The oxygen stoichiometries and structures of these oxides were determined by XRD and TPR results as followings; LaMnO$_{3.16}$(a = 5.507, c = 13.329 $\AA$, hexagonal), LaFeO$_{3.17}$(a = 5.554, b = 5.555, c = 7.863 $\AA$, orthorhomibic), LaCoO$_{3.0}$(a = 5.436, c = 13.095 $\AA$, hexagonal). The temperature programmed reduction(TPR) experiments in static 300 torr H$_2$ atmosphere shows that the reduction reaction of LaBO$_3$(B = Mn, Fe, Co) proceeds into two stages, and thermal stabilities of these oxides decreased in the order of LaMnO$_3$ > LaFeO$_3$ > LaCoO$_3$. According to the kinetic analysis the lowest activation energy was obtained for LaCoO$_3$.

• Clean Technology
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• v.18 no.3
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• pp.259-264
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• 2012

Perovskite-type oxides were successfully prepared using malic acid method, characterized by TG/DTA, XRD, XPS, TEM and $H_2$-TPR and their catalytic activities for the combustion of benzene were determined. Almost of catalyst showed perovskite crystalline phase and 15-70 nm particle size. The $LaMnO_3$ catalysts showed the highest activity and the conversion reaches almost 100% at $350^{\circ}C$. The catalysts were modified to enhance the activity through substitution of metal into the A or B site of the perovskite oxides. In the $LaMnO_3$-type catalyst, the partial substitution of Sr into site the A-site enhanced the catalytic activity in the benzene combustion. In addition, the partial substitution of Co or Cu into site the B-site also enhanced the catalytic activity and the catalytic activity was in the order of Co > Cu > Fe in the $LaMn_{1-x}B_xO_3$ (B = Co, Fe, Cu) type catalyst.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.584-588
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• 2019

The catalytic combustion of particulate matter (PM) is one of the key technologies to meet emission standards of diesel engine system. Therefore, we herein suggest Ag loaded $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskite web catalyst. They were produced by the electrospinning method. FE-SEM, EDS mapping, XRD, XPS were studied to investigate the crystal and morphological structures of loaded Ag particles and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskite web catalyst. Following the catalytic soot oxidation, we found that the Ag loaded $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskiteweb catalyst showed the higher catalytic activities (e.g., $T_{50}=490^{\circ}C$) than the only $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskite web catalyst (e.g., $T_{50}=586^{\circ}C$). Thus, this finding suggests that Ag loaded $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskite web catalyst can be a promising candidate for enhancing the soot oxidation.

• Journal of Electrochemical Science and Technology
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• v.6 no.4
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• pp.121-130
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• 2015

The micro emulsion method has been successfully used for preparing perovskite LaCoO₃ with uniform, fine-shaped nanoparticles showing high activity as electro catalysts in oxygen reduction reactions (ORRs). They are, therefore, promising candidates for the air-cathode in metal-air rechargeable batteries. Since the activity of a catalyst is highly dependent on its specific surface area, nanoparticles of the perovskite catalyst are desirable for catalyzing both oxygen reduction and evolution reactions. Herein, LaCoO₃ powder was also prepared by sol-gel method for comparison, with a broad particle distribution and high agglomeration. The electro catalytic properties of LaCoO₃ and LaCoO₃-carbon Super P mixture layers toward the ORR were studied comparatively using the rotating disk electrode technique in 0.1 M KOH electrolyte to elucidate the effect of carbon Super P. Koutecky-Levich theory was applied to acquire the overall electron transfer number (n) during the ORR, calculated to be ~3.74 for the LaCoO₃-Super P mixture, quite close to the theoretical value (4.0), and ~2.7 for carbon-free LaCoO₃. A synergistic effect toward the ORR is observed when carbon is present in the LaCoO₃ layer. Carbon is assumed to be more than an additive, enhancing the electronic conductivity of the oxide catalyst. It is suggested that ORRs, catalyzed by the LaCoO₃-Super P mixture, are dominated by a 2+2-electron transfer pathway to form the final, hydroxyl ion product.