• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.145-149
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• 2015

The electrochemical behavior of $Nd_2O_3-La_2O_3-NiO$ mixed oxide including rare earth resources has been studied to synthesize $La_{0.5}Nd_{0.5}Ni_5$ alloy in a LiCl molten salt. The $Nd_2O_3-La_2O_3-NiO$ mixed oxide was converted to $NiNd_2O_4$ (spinel) and $LaNiO_3$ (perovskite) structures at a sintering temperature of $1100^{\circ}C$. The spinel and perovskite structures led a speed-up in the electrolytic reduction of the mixed oxide. Various reaction intermediates such as Ni, $NiLa_2O_4$ were observed during the electrochemical reduction by XRD analysis. A possible reaction route to $La_{0.5}Nd_{0.5}Ni_5$ in the LiCl molten salt was proposed based on the analysis result.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.757-761
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• 2019

The catalytic yields of POM to hydrogen over M(1)-Ni(5)/AlCeO₃ (M = La, Ce, Y) were investigated using a fixed bed flow reactor under atmosphere. The crystal phase behavior of reduced La(1)-Ni(5)/AlCeO₃ catalysts before and after the reaction were studied via XRD analysis. FESEM and EDS analyses were further performed to show the uniformed distribution of La, Ni, and Ce metal particles on the catalyst surface. XPS results showed O^2-, O₂^2- species and metal ions such as Ce³⁺, Ce⁴⁺, La³⁺ and Ni²⁺ etc. were on the catalyst surface. When 1 wt% of La was added to Ni(5)/AlCeO₃ catalyst, Ni2p_3/2 and Ce3d_5/2 increased 52.7 and 6.3%, respectively. The yield of hydrogen on the La(1)-Ni(5)/AlCeO₃ catalyst was 89.1%, which was much better than that of M(1)-Ni(5)/AlCeO₃ (M = Ce, Y). As Ce⁴⁺ ions of CeO₂ produced by the reaction of AlCeO₃ with oxygen were substitute to La³⁺, it made oxygen vacancies in the lattice and further improved the hydrogen yield by increasing the dispersion of Ni atoms with strong metal-support interaction (SMSI) effect.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.255-260
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• 1998

Metal hydrides, $LaNi_5$ and $LaNi_{4.5}Al_{0.5}$, were prepared using chemical synthetic method, and their physical properties were examined using various analytic techniques such as TGA, XRD, SEM and EDX. The activation of the chemically prepared $LaNi_5$ and $LaNi_{4.5}Al_{0.5}$ was achieved by two hydriding/dehydriding cycles only. The miasurements of P-C-T curves revealed that 6 and 5.5 hydrogen atoms were stored in LaNi5and $LaNi_{4.5}Al_{0.5}$, respectively. The hydriding reaction rated for $LaNi_{4.5}Al_{0.5}$ were measured by the method of initial rates. It was found that the shrinking unreacted core model could be applied for the analysis of hydriding kinetics of $LaNi_5$. The rate controlling step of this reaction was the dissociative chemisorption of hydrogen molecules on the surface of $LaNi_5$. The activation energy was $9.506kcal/mol-H_2$. The rates measured in the temperature range from 273 to 343K and in pressure difference ($P_o-P_{eq}$) range form 0.25 to 0.66atm could be expressed as the following equation ; $\frac{dX}{dt}=4.636(P_o-P_{eq})$ exp($\frac{-9506}{RT}$).

• Journal of the Korean Electrochemical Society
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• v.3 no.2
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• pp.121-126
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• 2000

The effect of electroless Ni and Cu plating on $LaNi_5$, $AB_5$ type hydrogen storage alloy was investigated by the various electrochemical techniques such as constant current charge-discharge test, cyclic voltammeoy, and a.c. impedance spectroscopy. Scanning electron microscopy and X-ray diffraction test were conducted for phenomenological logical analyses. Cyclic Voltammetry results show that activation characteristics, cycle life and reaction ,rate were improved through electroless Ni and Cu plating. Compared with bare $LaNi_5$ the charge transfer resistance of electrode was greatly reduced as charge-discharge cycle increases. Therefore, electroless Ni and Cu plating on $LaNi_5$ alloy tends to accelerate the early activation, increasing the cyclic lift of electrode.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.568-574
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• 1997

The effect of microencapsulation of maetal hydride (MH) with copper on the electrode performance of a Ni/MH battery has been investigated. The MH electrodes were prepared with a combination of cold press and paste methods. The discharge capacity of the electrode increased with an addition of small amounts if CMC into the electrode, but decreased when heat-treated in an oxygen-free nitrogen flow. The capacity of a Cu-coated $LaNi_5$ electrode was higher than that of LaNi5electrode. The discharge capacity of the electrode prepared with Cu-coated $LaNi_5$ increased with the increase of copper content in the electrode. It is considered that the increase of copper content enhanced the current density on the electrode surface, leading to the increase of the discharge capacity The MH electrode coated by an acidic electroless plating method showed much higher discharge capacity than that using an alkaline electroless plating method. The discharge capacity of the $LaNi_{4.5}Al_{0.5}$ electrode was higher than that of the $LaNi_5$ electrode. Also, the effect of microencapsulation on the deactivation of $LaNi_5$ was studied using an absorption-desorption cycle in CO-containing hydrogen.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.5
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• pp.419-426
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• 2018

$Ni-La_2O_3-Ce_{0.8}Zr_{0.2}O_2$ catalysts with various $La_2O_3$ loading were investigated for hydrogen production from steam reforming of methane (SRM). The $La_2O_3$ loading influenced the physicochemical properties of $Ni-La_2O_3-Ce_{0.8}Zr_{0.2}O_2$ catalysts such as BET surface area, Ni dispersion, Ni size and reducibility. Among the prepared catalysts, $Ni-70La_2O_3-Ce_{0.8}Zr_{0.2}O_2$ catalyst showed the highest activity and stability at a very high gas hourly space velocity (GHSV) of $932,556h^{-1}$. This is mainly due to high Ni dispersion, small Ni size and high reducibility.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.1
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• pp.25-31
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• 2018

To apply Sievert's type apparatus to thermal analysis of hydrogen absorption materials, the dehydrogenation of $LaNi_5$ system was investigated. As the initial wt% of hydrogen was increased from 0.44 to 1.24 wt%, the peak temperature of evolution rate shifted to higher temperature. However, with the initial wt% of hydrogen higher than 0.95 wt%, the peak temperature of evolution rate did not change. As the heating rate was increased, the peak temperature increased; the peak temperatures for heating rates 0.5, 1.0 and 1.5 K/min were 262.2, 264.1, and 265.9 K respectively. The Sievert's type automatic apparatus can be successively applied to the thermal analysis of $LaNi_5$ hydride.

• Transactions of the Korean hydrogen and new energy society
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• v.1 no.1
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• pp.15-23
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• 1989

The selective separation of hydrogen from gas mixture containing hydrogen was experimentally studied using $LaNi_5$. The capacity and the rate of hydrogen separation, the purity of recovered hydrogen and the optimum condition of the regeneration of deactivated $LaNi_5$ were investigated. The separation rate and the recovery ratio of hydrogen were slowly decreased with the increase of the number of hydrogen absorption cycle. It was found that this result comes from the deactivation of $LaNi_5$ partly because of the blocking of hydrocarbon compounds in the $LaNi_5$ lattice and partly because of the poisoning of $LaNi_5$ surface by carbon monoxide contained in the gas mixture. The optimum condition for the regeneration of deactivated $LaNi_5$ was obtained by heating in a vacuum to about 637 K. The recovery ratio of hydrogen at the optimum condition was observed to be about 80%. The rates of hydrogen separation were measured in the ${\alpha}$-phase and two phase regions. The rate equations could be expressed as follows ; ${\alpha}$ - phase : $$-\frac{dP{_{H_2}}}{dt}=9.836{\times}10^{-3}(P{_{H_2}}_{-P_{eq}})$$ two phase region : $$-\frac{dP_{H{_2}}}{dt}=1.6909{\times}10^2\exp(-17560/RT)(P{_{H_2}}_{-P_{eq}})$$.

• Clean Technology
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• v.5 no.2
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• pp.63-68
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• 1999

The activities of Ni(20wt%)/$La_2O_3$, Ni(20wt%)/${\gamma}-Al_2O_3$, and Ni(20wt%)/$SiO_2$ catalyst for $CO_2$ reforming of $CH_4$ were investigated in a fixed bed flow reactor under atmospheric condition. Catalyst characterization using XRD, TEM, SEM, BET analysis were also conducted. The catalytic activity of Ni(20wt%)/$La_2O_3$ catalyst has relatively superior to that of Ni(20wt%)/${\gamma}-Al_2O_3$ and Ni(20wt%)/$SiO_2$ catalyst. The good activity of Ni(20wt%)/$La_2O_3$ catalyst seems to depend on reduced $Ni^{\circ}$ phases of NiO($\rightarrow$ Ni + O), $LaNiO_3$($\rightarrow$ $Ni+La_2O_3$), Ni crystalline phases, and decoration of Ni phases by lanthanum species is also an important factor. Ni(20wt%)/${\gamma}-Al_2O_3$ and Ni(20wt%)/$SiO_2$ catalyst due to surface acidity resulted in the deposition of wisker type and encapsulate carbon on the surface of catalyst, but Ni(20wt%)/$La_2O_3$ catalyst did not show carbon on the surface of catalyst up to 8.5hr reaction.

• 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.