Electrochemical Performance Of La0 Research Articles

Construction of a metal–oxide interface through alloy nanoparticles to enhance CO2 electrolysis

The figure shows the basic mechanism of SOEC electrolysis of CO2 and the electrochemical performance of La0.7Sr0.3Cr0.5Mn0.5(FeCo)xO3−δ(LSCM(FeCo)x). Among them, the current density of LSCM(FeCo)0.075 at 1.6 V reaches 0.74 A cm−2.

Structures and electrochemical performances of La0.7Sm0.3MgNi3·6Co0.4 + xwt.%Ni (x = 0,5,10,15,20) alloys applied to Ni-MH battery

The La–Mg–Ni–Co-based AB2-type alloys, namely La0.7Sm0.3MgNi3·6Co0.4xwt.%Ni (x = 0,5,10, 15, 20), were synthesized through ball milling. The study focused on investigating the impact of Ni content on the structures and electrochemical properties. The structures of the samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Transmission electron microscope (TEM). It has been demonstrated that the experimental samples consist of a primary phase, LaMgNi4, and a secondary phase, LaNi5. The abundance of phases undergoes significant changes with variations in Ni content, while the phase composition remains constant. The results indicate that a rise in Ni concentration results in an elevation of the LaNi5 phase and a reduction of the LaMgNi4 phase. Additionally, ball milling and the addition of nickel contribute to the refinement of the alloy grains. As the nickel concentration reached 20 wt%, the cycle retention rate(S30) of the composite alloy electrode achieved its maximum value of 73.42 %. In addition, the electrochemical kinetic test findings demonstrated that the maximum D value of the hydrogen diffusion system was 1.807 × 10−10 cm2/s and that the maximum current density of the composite hydrogen storage alloy electrode was 723 mA/g when x = 0 wt%.

Improving the cathodic performance of La0.7Sr1.3CoO4 by substituting Ni in Co sites for intermediate solid oxide fuel cells application

In this study, the effect of Ni substitution in Co sites of La0.7Sr1.3CoO4 Ruddlesden-Popper oxides was investigated, as cathode for using in solid oxide fuel cells. Structural and lattice dynamic analyses revealed that La0.7Sr1.3Co1−xNixO4 (x = 0, 0.1, 0.3 and 0.5) had tetragonal structure and the lattice volume decreased as a results of Co3+ stabilization in low spin state with substituting Ni ions in Co sites. In addition, the x-ray photo electron spectroscopy (XPS) indicated that Co4+/Co3+ ratio decreases in these synthesized powders with enhancement of Ni dopant, while the oxygen vacancy and the oxygen adsorption in the samples increased. The electrochemical performance of La0.7Sr1.3Co1−xNixO4 synthesized powders was studied using electrochemical impedance analysis of the symmetrical cells. The electrochemical processes were determined by employing distribution of relaxation time (DRT) analysis. It was revealed that doping of La0.7Sr1.3CoO4 with Ni leads to decreasing the polarization area specific resistance from 1.2 Ω cm2 for x = 0 to 0.36 Ω cm2 for x = 0.5 at 800 °C. So, it can be concluded that by Ni substitution in Co sites the cathodic performance of La0.7Sr1.3CoO4 improves significantly and these compounds can be considered as suitable cathode candidates to be used in IT-SOFC.

Impact of the Synthesis Method on Electrochemical Performance of La0.5Sr0.5MnO3 Perovskite Oxide as a Cathode Material in Alkaline Fuel Cells

Impact of the Synthesis Method on Electrochemical Performance of La0.5Sr0.5MnO3 Perovskite Oxide as a Cathode Material in Alkaline Fuel Cells

Electrochemical performance of La0.65Sr0.35MnO3 oxygen electrode with alternately infiltrated Sm0.5Sr0.5CoO3-δ and Sm0.2Ce0.8O1.9 nanoparticles for reversible solid oxide cells

La1-xSrxMnO3 is a well-known oxygen electrode for reversible solid oxide cells (RSOCs). However, its poor ionic conductivity limits its performance in redox reaction. In this study, we selected Sm0.5Sr0.5CoO3-δ (SSC) as catalyst and Sm0.2Ce0.8O1.9 (SDC) as ionic conductor and sintering inhibitor to co-modify the La0.65Sr0.35MnO3 (LSM) oxygen electrode through an alternate infiltration method. The infiltration sequence of SSC and SDC showed an influence on the morphology and performance of LSM oxygen electrode, and the influence was gradually weakened with the increasing infiltration time. The polarization resistance of the alternately infiltrated LSM-SSC/SDC electrode was 0.08 Ω cm2 at 800 °C in air, which was 3.36% of the LSM electrode (2.38 Ω cm2). The Ni-YSZ/YSZ/LSM-SSC/SDC single cell attained a maximum power density of 1205 mW cm−2 in SOFC mode at 800 °C, which was 8.73 times more than the cell with LSM electrode. The current density achieved 1620 mA .cm−2 under 1.5 V at 800 °C in SOEC mode and the H2 generation rate was 3.47 times of the LSM oxygen electrode.

Study of (La,Sr)(Ti,Ni)O3-δ materials for symmetrical Solid Oxide Cell electrode - Part C: Electrical and electrochemical behavior

(La,Sr)(Ti,Ni)O3 compounds have been characterized as air and hydrogen electrode for symmetrical Solid Oxide Cells. While the materials are thermomechanically compatible with 8YSZ electrolyte, the reactivity tests confirm the formation of an insulating pyrochlore La2Zr2O7, redhibitory for the electrochemical properties. Concerning the electrical behavior, a Ti/Ni = 50/50 ratio is the best option for high electrical conductivity in both air and hydrogen, in view of the targeted application as symmetric cell electrode. The electrochemical performance of La0.875Sr0.125Ti0.5Ni0.5O3 (25LSTN50) material is similar to the materials that have been proposed in literature for SOCs cathode and anode at the same time, but the polarization resistances are still higher than the state-of-the-art hydrogen or air electrodes of classical asymmetric cells.

Performance of La0.5Sr1.5MnO4±δ Ruddlesden-Popper manganite as electrode material for symmetrical solid oxide fuel cells. Part B. the hydrogen oxidation reaction

The electrochemical performance of La0.5Sr1.5MnO4±δ (L5S15M) in reducing atmosphere was investigated using Electrochemical Impedance Spectroscopy (EIS) measurements on Au/L5S15M/GDC/YSZ/GDC/L5S15M/Au symmetrical cell. In this research, the electrochemical performance of symmetrical cells sintered at different temperatures cells was evaluated in various reducing atmospheres: 3% H2/Ar (3% H2O), dry 3% H2/Ar, and pure H2 (3% H2O). The lowest values for the area specific resistance (ASR) were acquired for the L5S15M electrode sintered at 1150 °C. For the hydrogen oxidation reaction, three rate limiting processes were identified and for all the electrode elaboration conditions, the low frequency response assigned to surface diffusion represents the highest contribution to the total polarization resistance.

Oxygen diffusion and electrochemical performance of La0.6−xSr0.4BaxCo1−yFeyO3−δ

La0.6−xSr0.4BaxCo1−yFeyO3−δ (x = 0, 0.2, y = 0.1, 0.2, 0.3, 0.4) were prepared by the glycine–nitrate process. The electrochemical property and oxygen diffusion behavior of La0.6−xSr0.4BaxCo1−yFeyO3−δ were investigated. The electrochemical impedance spectroscopy analysis suggests that doping with an appropriate amount of iron and barium improves the catalytic performance. La0.4Sr0.4Ba0.2Co0.9Fe0.1O3−δ calcined at 950 °C exhibits the minimum polarization resistance of 0.0349 Ω cm2 at 750 °C. The doping of Fe improves the sintering performance. The crystalline size of La0.6−xSr0.4BaxCo1−yFeyO3−δ becomes smaller with the doping amount of Ba, which increase the number of active sites. The doping of Ba decreases the oxygen vacancy formation energy and increases the oxygen vacancy concentration, which accelerates the oxygen diffusion. Further, the single cell performance for La0.4Sr0.4Ba0.2Co0.9Fe0.1O3−δ as cathode shows the maximum power density of 539.49 W cm−2 at 750 °C.

Electrochemical performance of La0.8Sr0.2MnO3 oxygen electrode promoted by Ruddlesden‐Popper structured La2NiO4

AbstractThe effects of introducing La2NiO4 nanocatalyst on the electrochemical performance of La0.8Sr0.2MnO3 are investigated under solid oxide electrolysis cell and fuel cell modes, as well as open circuit voltage. Extracted data from impedance spectroscopy are interpreted with the analysis of distribution of relaxation times. La2NiO4 infiltration effectively reduces the activation energy of the oxygen reactions from 1.35 to 0.99 eV. It also changes the rate controlling process of the overall reaction. Polarization behavior of La2NiO4‐infiltrated La0.8Sr0.2MnO3 electrode shows superior performance under electrolysis mode compared to the fuel cell mode. Drastic increase in the size of low frequency arc during anodic current passage in the non‐infiltrated La0.8Sr0.2MnO3 electrode is hampered by infiltration of La2NiO4 nanocatalyst. By applying anodic current on infiltrated La0.8Sr0.2MnO3, no displacement is observed in the position of high frequency peaks in the distribution of relaxation time graphs and only a small increase in height occurs for the low frequency arc. Additionally, La2NiO4‐infiltrated electrode impressively decreases overpotential by 74% compared to the non‐infiltrated one under electrolysis mode at 800°C.

Electrochemical performance of La0.6Sr0.4Co0.2Fe0.8O3–Ce0.9Gd0.1O2-δ composite SOFC cathodes fabricated by electrocatalyst and/or electrocatalyst-ionic conductor infiltration

Infiltration of electrocatalyst precursor solutions into previously sintered porous ionic conductor scaffolds has been used recently as an alternative method to the conventional co-sintering route to fabricate electrocatalyst-ionic conductor composites for solid oxide fuel cell (SOFC) cathode applications. However, the aqueous nitrate solutions generally used to perform the infiltration process results in electrocatalyst precipitates that are disconnected from each other, yielding poor electrode performance. In this work, polymeric electrocatalyst (La0.6Sr0.4Co0.2Fe0.8O3—LSCF) precursors that produce interconnected thin films upon heat treatment were used to infiltrate porous ionic conductor Ce0.9Gd0.1O2-δ (GDC) scaffolds to overcome these issues. In addition, for the first time in the literature, a mixture of LSCF and GDC polymeric precursors, which would yield LSCF–GDC nanocomposite coatings on the grains of the porous GDC scaffold were used as the infiltration solution. Thus, further enhancement of the electrocatalyst/ionic conductor interfacial area and achievement of improved electrode performance was aimed. As a result of the optimization studies, the lowest measured area specific polarization resistance (ASRcathode) values of 0.47 and 0.73 Ω.cm2 were obtained for polymeric LSCF+GDC and LSCF precursor infiltrations respectively at 700 °C, in air. In addition, LSCF+GDC infiltration yielded electrodes with much improved long-term stability in comparison to those obtained by LSCF infiltration.

Cobalt-Free Perovskite Oxide La0.6Sr0.4Fe0.8Ni0.2O3−δ as Active and Robust Oxygen Electrode for Reversible Solid Oxide Cells

Reversible solid oxide cells have received increasing attention due to high efficiency. Cobalt-free perovskite electrode has compatible thermal expansion coefficient matching with the electrolyte and the reversible operation to inhibit the segregation of Sr. Herein a novel cobalt-free La0.6Sr0.4Fe0.8Ni0.2O3−δ perovskite is developed and investigated as oxygen electrode for reversible solid oxide cells. The electrochemical performance of La0.6Sr0.4Fe0.8Ni0.2O3−δ oxygen electrode in fuel cell mode and electrolysis mode is investigated in detail. The maximum power density of 961 mW cm–2 and polarization resistance of 0.142 Ω cm2 at 800 °C can be achieved in fuel cell mode. While the cell is operated in electrolysis mode, the current density ranges from 0.53 A cm–2 at 750 °C to 1.09 A cm–2 at 850 °C with 50 vol % absolute humidity at 1.3 V, and the hydrogen generation rate can reach up to 1348.5 mL (cm2 h)−1 with 90 vol % absolute humidity at 800 °C. The reversible solid oxide cells show excellent reversibili...

Performance of La0.5Sr1.5MnO4±δ Ruddlesden-Popper manganite as electrode material for symmetrical solid oxide fuel cells. Part A. The oxygen reduction reaction

The electrochemical performance of La0.5Sr1.5MnO4±δ (L5S15 M) as SOFC cathode was studied using Electrochemical Impedance Spectroscopy (EIS) measurements. The influence of the sintering temperature on the electrochemical performance was examined in air for Au/L5S15 M/GDC/YSZ/GDC/L5S15 M/Au symmetrical cell. For the oxygen reduction reaction, the electron transfer between the electrode and oxygen, and the incorporation of oxygen ions into the electrode are the main controlling processes of oxygen reduction reaction for electrodes sintered at 1150 and 1200 °C. Increasing the sintering temperature up to 1250 °C increases the Sr diffusion through GDC interlayer, which leads to Sr accumulation at the GDC/YSZ interface with SrZrO3 formation and subsequent cell performance degradation. The lowest area specific resistance (ASR) values was obtained for the L5S15 M electrode sintered at 1150 °C.

Effect of grain size on the electrical properties of strontium and magnesium doped lanthanum gallate electrolytes

The aim of this research is to investigate the effect of average grain size on electrical and electrochemical performances of La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM). For this purpose, the glycine-nitrate method is used to synthesize the LSGM electrolytes and subsequently sintered at 1350, 1400, 1450 and 1500 °C in a muffle furnace with temperature holding for 10 h. XRD study reveals that all of the sintered LSGM ceramic electrolytes crystallize to a single phase of orthorhombic perovskite structure without any impurity phases. Results from scanning electron microscopy (SEM) study demonstrate that increasing sintering temperature from 1350 to 1500 °C leads to increase in average grain size from 1.02 to 4.87 μm. Electrochemical AC impedance tests show that the bulk resistance is nearly independent on the average grain size, and the grain boundary resistance changes because of the difference in the average grain size. The LSGM sample sintered at 1500 °C achieves the maximum electrical conductivity 9.19 × 10−2 S cm−1 at 800 °C. The maximum power density of assembled cell with LSGM sintered at 1500 °C as an electrolyte is 0.76 W cm−2 at 800 °C in air atmosphere.

Effect of Infiltration of Barium Carbonate Nanoparticles on the Electrochemical Performance of La0.6Sr0.4Co0.2Fe0.8O3−δ Cathodes for Protonic Ceramic Fuel Cells

BaCO3 nanoparticles were infiltrated into a La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) electrode as a synergistic catalyst to enhance the performance of proton conducting solid oxide fuel cells (H-SOFCs). Electrochemical impedance analysis showed that the polarization resistance was dramatically reduced by nearly 75% from 1.123 Ω cm2 to 0.293 Ω cm2 at 700°C after infiltration of BaCO3 nanoparticles. The chemical stability between the BaCO3 and LSCF electrode was investigated by running a long-term 300-h test, during which the polarization resistance exhibited only minor degradation (2.22–2.20 Ω cm2). In addition, single cells with infiltrated LSCF electrode and BaCe0.7Zr0.1Y0.1Yb0.1O3−δ (BCZYYb) electrolyte yielded a maximum power density of 404 mW cm−2 at 700°C, much higher than cells with a bare LSCF electrode (268 mW cm−2 at 700°C). BaCO3 demonstrated promising performance enhancements of LSCF electrodes for H-SOFCs and warrants further development.

Fabrication and electrochemical performance of La0.5Sr0.5CoO3 impregnated porous YSZ cathode

La0.5Sr0.5CoO3-yttria-stabilized zirconia (LSCO-YSZ) composite cathode for solid oxide fuel cell (SOFC) has been fabricated by wet impregnation method. Nitrate precursors of La, Sr, and Co have been impregnated into the pre-sintered porous YSZ matrix, which is converted into LSCO phase after calcination at 850 °C in the presence of glycine as confirmed from X-ray diffraction. LSCO of 5, 7, and 10 wt% impregnated porous YSZ have been electrochemically characterized using 2-probe AC conductivity method. Maximum ionic conductivity of 0.27 S/cm at 800 °C and activation energy of 0.15 eV between 600 and 800 °C have been observed for 10 wt% LSCO-YSZ cathode. Area-specific resistance of 1.01 Ω cm2 at 800 °C is estimated for the electrolyte-supported half-cell (10 wt% LSCO-YSZ/YSZ). After testing the LSCO-YSZ cathode matrix, the electrolyte-supported full cell (10 wt% LSCO-YSZ/YSZ/NiO-YSZ) has been tested and produced maximum power density 51.12 mW/cm2 (109.38 mA/cm2) at 800 °C. The electrolyte-supported full cell exhibited 6 Ω cm2 electrode polarization at 800 °C in H2, which is in higher side leading to low performance. LSCO-YSZ/YSZ/NiO-YSZ SOFC found to give stable performance up to 2 h and scanning electron microscopy analysis has been carried out before and after cell testing to assess the morphological changes.

Magnetic field effect on the electrochemical performance of La0.7Sr0.3MnO3-δ cathodes

La 0.7 Sr 0.3 MnO 3 − δ (LSM) magnetic properties are exploited through the application of a magnetic field, resulting in a significant decrease of the cathode polarization resistance, a crucial component of high temperature solid oxide fuel cells. The magnetic field is applied during the drying process after the deposition of LSM cathodes by screen-printing on a Gd0.1Ce0.9O1.95 (GDC) electrolyte. This specific process aims to decrease the cathode polarization resistance of solid oxide fuel cells. X-ray diffraction patterns show a structural modification triggered by the magnetic field. LSM cathode performance is investigated over a temperature range of 700–800 °C by impedance spectroscopy. The measured electrode area specific resistance (ASR) of a LSM/GDC/LSM symmetric half-cell without and with magnetic field was 0.30 Ω cm2 and 0.20 Ω cm2, respectively, at 800 °C. The ASR value was therefore decreased by 33% with the magnetic field effect. This behaviour may be attributed to LSM grain reorientation, microstructure change, and tortuosity modification of LSM cathodes.

Effect of annealing temperature on microstructures and electrochemical performances of La0.75Mg0.25Ni3.05Co0.2Al0.1Mo0.15 hydrogen storage alloy

The effect of annealing temperature on microstructures and electrochemical performances of La0.75Mg0.25Ni3.05Co0.2Al0.1Mo0.15 hydrogen storage alloy is investigated. The alloys was prepared via vacuum induction melting followed by annealing treatment for 8 h at the temperatures of 1073, 1123, 1173, and 1223 K, respectively. The major phases in the as-cast and annealed alloys are consisted of (La, Mg)2Ni7, (La, Mg)5Ni19 and LaNi5 phase while the residual phase MoNi4 existing in the as-cast alloy decomposes into Mo phase after heat treatment. Annealing treatment facilitates LaNi5 phase transforms into (La, Mg)2Ni7 and (La, Mg)5Ni19 phase, but the tendency is suppressed as annealing temperature increases. Furthermore, the annealed alloys have more homogeneous phase distribution and better crystallization. Electrochemical experiments manifest that annealing treatment is beneficial for the increase of the maximum discharge capacity while impairs the activation ability of the alloy electrodes. The cycle life is prolonged in consequence of the homogeneous phase distribution created by annealing treatment at 1073–1173 K. Nonetheless, annealing treatment distinctly deteriorates the kinetic property of the alloys electrodes which is mainly ascribed to the disappearance of MoNi4 phase with high-efficiency electrocatalytic activity. The comprehensive electrochemical properties of the annealed alloy at 1173 K presents a good balance between superior discharge capacity, kinetic property and remarkably improved cyclic stability.

Microstructural evolution and electrochemical properties of the ultra-high pressure treated La0.70Mg0.30Ni3.3 hydrogen storage alloy

This research highlighted the effects of ultra-high pressure (UHP) technique (1–5 GPa) on microstructural evolution and electrochemical performances of La0.70Mg0.30Ni3.3 alloy. Structure analysis showed that the as-cast alloy consisted of (La,Mg)Ni3, (La,Mg)2Ni7, (La,Mg)5Ni19, LaNi5 and LaMgNi4 phases. For all the UHP treated alloys, (La,Mg)5Ni19 phase disappeared via converting into (La,Mg)2Ni7 and LaNi5 phases. At 1 GPa, LaNi5 phase and LaMgNi4 phase fully transformed into (La,Mg)Ni3 and (La,Mg)2Ni7 phases by the peritectic reactions. However, when the pressure was 3 GPa and 5 GPa, the peritectic reactions were uncompleted for the atom diffusion was hindered, which not only caused the minor residual of LaNi5 and LaMgNi4 phases in the alloys, but also resulted in the increase of (La,Mg)Ni3 phase and the decrease of (La,Mg)2Ni7 phase. Electrochemical measurements displayed that the cyclic stability of alloy electrode treated at 1 GPa increased by 8.7% comparing with that of the as-cast alloy electrode, while the cyclic stability reduced when the pressure increased to 3 GPa and 5 GPa. This indicated that the appropriate UHP treatment was favorable for the improvement of the cycle life of alloy electrode. The high rate dischargeability (HRD) of alloy electrodes gradually decreased with the pressure increasing, which mainly resulted from the decrease of the hydrogen diffusion coefficient.

Effect of non-stoichiometry on microstructure and electrochemical performance of La0.8GdxMg0.2Ni3.15Co0.25Al0.1 (x = 0–0.4) hydrogen storage alloys

La0.8GdxMg0.2Ni3.15Co0.25Al0.1 (x = 0–0.4) hydrogen storage alloys are prepared by induction melting followed by annealing treatment at 1173 K for 8 h. The effects of non-stoichiometry on phase structure and electrochemical properties with Gd addition are investigated systematically. The results show that Gd addition exerts significant effects on the phase component of the alloys. A appropriate amount of Gd addition (x = 0.1) can increase the abundance of (La,Mg)2Ni7-type phase while that of (La,Mg)5Ni19-type phase decreases. The further increase of Gd content (x ≥ 0.2) results in appearance of (La,Mg)Ni3-type, (La,Mg)7Ni16-type and La2MgNi2-type phases. Electrochemical tests reveal that the maximum discharge capacity and cycle life of the alloy electrodes can benefit from the right amount of Gd addition (x = 0.1), both of which are deteriorative with further increasing Gd content. However, the excess amount of Gd (x ≥ 0.2) jeopardizes the high rate dischargeability of the alloy electrodes obviously owing to the increase of charge transfer resistance on alloy surface.

Effects of Cu Substitution for Sn on the Electrochemical Performance of La0.7Mg0.3Al0.3Mn0.4Sn0.5−xCuxNi3.8 (x = 0–0.5) Alloys for Ni-MH Batteries

The effects of substitution of Cu for Sn on the electrochemical discharge capacity performance of La0.7Mg0.3Al0.3Mn0.4Sn0.5−xCuxNi3.8 (x = 0.0, 0.1, 0.2, 0.3, and 0.5) negative electrode alloys were investigated. Results indicate that increasing Cu content enhanced electrochemical behavior by increasing the maximum discharge capacity from 239.8 mA·h/g (x = 0) to 305.2 mA·h/g (x = 0.5), the discharge capacity retention at the 100th cycle from 78.0% (x = 0) to 81.8% (x = 0.5), and the high rate dischargeability (HRD) from 25.7% (x = 0) to 80.6% (x = 0.5).