Strontium-doped Lanthanum Research Articles

Effect of Steam to Carbon Dioxide Ratio on the Performance of a Solid Oxide Cell for H2O/CO2 Co-Electrolysis

The mixture of H2 and CO, the so-called syngas, is the value-added product of H2O and CO2 co-electrolysis and the feedstock for the production of value-added chemicals (mainly through Fischer-Tropsch). The H2/CO ratio determines the process in which syngas will be utilized and the type of chemicals it will produce. In the present work, we investigate the effect of H2O/CO2 (steam/carbon dioxide, S/C) ratio of 0.5, 1 and 2 in the feed, on the electrochemical performance of an 8YSZ electrolyte-supported solid oxide cell and the H2/CO ratio in the outlet, under co-electrolysis at 900 °C. The B-site iron doped lanthanum strontium chromite La0.75Sr0.25Cr0.9Fe0.1O3-δ (LSCF) is used as fuel electrode material while as oxygen electrode the state-of-the art LSM perovskite is employed. LSCF is a mixed ionic-electronic conductor (MIEC) operating both under a reducing and oxidizing atmosphere. The cell is electrochemically characterized under co-electrolysis conditions both in the presence and absence of hydrogen in the feed of the steam and carbon dioxide mixtures. The results indicate that under the same concentration of hydrogen and different S/C ratios, the same electrochemical performance with a maximum current density of approximately 400 mA cm-2 is observed. However, increasing p(H2) in the feed results in higher OCV, smaller iV slope and Rp values. Furthermore, the maximum current density obtained from the cell does not seem to be affected by whether H2 is present or absent from the fuel electrode feed but has a significant effect on the H2/CO ratio in the analyzed outlet stream. Moreover, the H2/CO ratio seems to be identical under polarization at different current density values. Remarkably, the performance of the LSCF perovskite fuel electrode is not compromised by the exposure to oxidizing conditions, showcasing that this class of electrocatalysts retains their reactivity in oxidizing, reducing, and humid environments.

Facile and composition controllable synthesis of lanthanum-doped strontium titanate via peroxide route

ABSTRACT Lanthanum-doped strontium titanate powder, La0.05Sr0.95TiO3+δ, was fabricated by peroxide-based route and calcination of freshly prepared precipitate and precipitate after ageing was carried out. The starting titanium precursor was titanium nitride, which underwent the reaction to form titanium peroxohydroxide and then compound containing strontium and lanthanum. A perovskite structure of strontium titanate with 5 mol-% doped lanthanum was obtained after calcination of the freshly-prepared precipitate at 500°C. However, the ageing powder revealed the presence of the second phase of strontium carbonate after calcination at the same condition. Thermogravimetric results showed that the decomposition of ammonia promoted a reaction to form the pure phase of ceramic oxide only in the freshly calcined sample.

A robust fluorine-containing ceramic cathode for direct CO2 electrolysis in solid oxide electrolysis cells

Strontium-doped lanthanum ferrite (LSF) is a potential ceramic cathode for direct CO2 electrolysis in solid oxide electrolysis cells (SOECs), but its application is limited by insufficient catalytic activity and stability in CO2-containing atmospheres. Herein, a novel strategy is proposed to enhance the electrolytic performance as well as chemical stability, achieved by doping F into the O-site of the perovskite LSF. Doping F does not change the phase structure but reduces the cell volume and improves the chemical stability in a CO2-rich atmosphere. Importantly, F doping favors oxygen vacancy formation, increases oxygen vacancy concentration, and enhances the CO2 adsorption capability. Meanwhile, doping with F greatly improves the kinetics of the CO2 reduction reaction. For example, kchem increases by 78% from 3.49 × 10−4 cm s−1 to 6.24 × 10−4 cm s−1, and Dchem doubles from 4.68 × 10−5 cm2 s−1 to 9.45 × 10−5 cm2 s−1. Consequently, doping F significantly increases the electrochemical performance, such as reducing Rp by 52.2% from 0.226 Ω cm2 to 0.108 Ω cm2 at 800 °C. As a result, the single cell with the F-containing cathode exhibits an extremely high current density of 2.58 A cm−2 at 800 °C and 1.5 V, as well as excellent durability over 200 h for direct CO2 electrolysis in SOECs.

The effect of synthesis method on oxygen nonstoichiometry and electrical conductivity of Sr-doped lanthanum manganites

The strontium-doped lanthanum manganites (La1-xSrxMnO3, LSMO) have potential use in devices for energy conversion and storage due to their chemical stability and high electrical conductivity. In this study, LSMO (x = 0, 0.1, 0.2, 0.3) were prepared by the citrate-nitrate autocombustion (CNA) and coprecipitation synthesis. The formation of the LSMO phase was confirmed by X-ray diffraction and the lattice parameters were determined by Rietveld refinement analysis. The oxygen nonstoichiometry in samples was determined by permanganate titration. The results of electrical conductivity measurement have shown semiconductor behaviuor in all samples, with conductivity rising with temperature and Sr-amount. Furthermore, it was observed that LSMO samples prepared by the coprecipitation method possess higher conductivity than samples prepared with the CNA method due to the higher oxygen nonstoichiometry. Electrical conductivities of all LSMO samples were in 10−2–0.45 Ω−1 cm−1 range, which is comparable to the conductivity of Si.

Microwave sintering study of strontium-doped lanthanum manganite in a single-mode microwave with electric and magnetic field at 2.45 GHz

The objective of this work is to study the changes in the physical and mechanical properties of strontium-doped lanthanum manganite (LSM) material and LSM-YSZ (ZrO2 doped with 8 mol% yttria) composite, obtained by colloidal processing and sintered by 2.45 GHz microwave sintering at 1200 and 1300 °C using two different single-mode cavities. One circular cavity with TE111 mode that has maximum in the electric field (E-field) and one rectangular cavity with TE102 mode that has maximum in the magnetic field (H-field). As compared to conventional sintering at 1300 and 1400 °C, the microwave-heated samples exhibited a denser structure for shorter sintering times. LSM-based materials showed higher heating behavior in H-field, which translates into higher energy absorption. This fact can be attributed to an electromagnetic pressure induced by the combined effect of current loops subjected to H-field. Therefore, the interaction between the material and the electromagnetic waves depends on the dominant field of them.

Smart Bone Graft Composite for Cancer Therapy Using Magnetic Hyperthermia

Magnetic hyperthermia (MHT) is a therapy that uses the heat generated by a magnetic material for cancer treatment. Magnetite nanoparticles are the most used materials in MHT. However, magnetite has a high Curie temperature (Tc~580 °C), and its use may generate local superheating. To overcome this problem, strontium-doped lanthanum manganite could replace magnetite because it shows a Tc near the ideal range (42–45 °C). In this study, we developed a smart composite formed by an F18 bioactive glass matrix with different amounts of Lanthanum-Strontium Manganite (LSM) powder (5, 10, 20, and 30 wt.% LSM). The effect of LSM addition was analyzed in terms of sinterability, magnetic properties, heating ability under a magnetic field, and in vitro bioactivity. The saturation magnetization (Ms) and remanent magnetization (Mr) increased by the LSM content, the confinement of LSM particles within the bioactive glass matrix also caused an increase in Tc. Calorimetry evaluation revealed a temperature increase from 5 °C (composition LSM5) to 15 °C (LSM30). The specific absorption rates were also calculated. Bioactivity measurements demonstrated HCA formation on the surface of all the composites in up to 15 days. The best material reached 40 °C, demonstrating the proof of concept sought in this research. Therefore, these composites have great potential for bone cancer therapy and should be further explored.

Simultaneous oxidation of aromatic compounds using Sr‐doped lanthanum manganites as catalysts

Strontium-doped lanthanum manganites, La1-xSrxMnO3 (LSMO), are promising and affordable catalysts for oxidative degradation of volatile organic compounds. LSMO catalysts (x = 0, .1, .2, and .3) were prepared by the citrate-nitrate autocombustion (CNA) and coprecipitation synthesis. The phase composition was confirmed by X-ray diffraction and Rietveld refinement analysis, while the oxygen content was determined by Mohr's salt permanganate titration. Morphology and porosity of prepared catalysts was correlated to catalytic oxidation of benzene, toluene, ethylbenzene and o-xylene. It was observed that both synthesis methods yielded catalysts of similar average pore size diameter and specific surface area, but the pore size distribution differed: CNA-prepared catalysts had a multimodal pore size distribution, while the coprecipitated ones had a single maximum at 4 nm. Catalysts prepared by the CNA method have shown a higher catalytic activity in the temperature range 373–723 K, as the presence of Mn3+/Mn4+ mixed valences increased their reducibility.

Investigation of an Impedimetric LaSrMnO3-Au/Y2O3-ZrO2-Al2O3 Composite NOx Sensor.

Composite NOx sensors were fabricated by combining partially and fully stabilized yttria-doped zirconia with alumina forming a composite electrolyte, Y2O3-ZrO2-Al2O3, and strontium-doped lanthanum manganese oxide mixed with gold to form the composite sensing electrode, La0.8 Sr0.2MnO3-Au. A surface chemistry analysis of the composite sensor was conducted to interpret defects and the structural phases present at the Y2O3-ZrO2-Al2O3 electrolyte, as well as the charge conduction mechanism at the LaSrMnO3-Au electrode surface. Based on the surface chemistry analysis, ionic and electronic transport properties, and microstructural features of sensor components, the working principle was described for NOx sensing at the composite sensor. The role of the composite materials on the NOx sensing response, cross-sensitivity to O2, H2O, CO, CO2, and CH4, and the response/recovery rates relative to sensor accuracy were characterized by operating the composite sensors via the impedimetric method. The composite sensors were operated at temperatures ranging from 575 to 675 °C in dry and humidified gas environments with NO and NO2 concentrations varying from 0 to 100 ppm, where the balance gas was N2. It was found that the microstructure of the composite NOx sensor electrolyte and sensing electrode had a significant effect on interfacial reactions at the triple phase boundary, as well as the density of active sites for oxygen reactions. Overall, the composite NOx sensor microstructure enabled a high NOx sensing response, along with low cross-sensitivity to O2, CO, CO2, and CH4, and promoted NO detection down to 2 ppm.

A Study of the Electrochemical Characteristics of Single-Chamber Solid Oxide Fuel Cells Based on Platinum and Strontium-Doped Lanthanum Manganite Electrodes and Fed with a Methane–Air Mixture

A Study of the Electrochemical Characteristics of Single-Chamber Solid Oxide Fuel Cells Based on Platinum and Strontium-Doped Lanthanum Manganite Electrodes and Fed with a Methane–Air Mixture

Improved electrocatalytic properties of strontium-doped lanthanum nickelate cathodes by infiltrating samarium-doped ceria

Improved electrocatalytic properties of strontium-doped lanthanum nickelate cathodes by infiltrating samarium-doped ceria

Preparation and Particle Size Study of Cobalt Substituted Strontium Doped Lanthanum Manganate Films by Sol-gel and Heat Treatment Method

In order to study the effect of B-position element substitution on strontium doped lanthanum manganate microstructure and resistivity temperature property, the cobalt substituted strontium doped lanthanum manganate ceramic powders with La0.6Sr0.4CoxMn1-xO3 as the main component was prepared by sol gel method combined with heat treatment process at first, then the cobalt substituted strontium doped lanthanum manganate films was prepared by silk-screen printing on the Alumina ceramic substrate. The results showed that when the x value sequentially varied from 0 to 0.2,0.4,0.6,0.8, the particle size property of films would be changed by the change of the crystal structure, which was produced by the B-position cobalt substitution. It could be seen from the results that the average radius of the five powders were concentrated in the range of 16.4-19.6nm.

Enhanced Catalytic Performance of Strontium-Doped Lanthanum Manganites by the Presence of Molybdenum Oxides for Electro-Reduction of Hydrogen Peroxide

In this work, two catalysts, lanthanum manganite strontium-doped perovskite without (LSM) and with (LSMMO) mixed molybdenum oxides, were synthesized by the sol-gel route and deposited by immersion in carbon cloth substrates. Their performance as cathodes in the hydrogen peroxide reduction reaction (HPRR) and oxygen reduction reaction (ORR) was investigated through cyclic voltammetry and electrochemical impedance spectroscopy, the electrocatalytic efficiency of these electrodes in the HPRR was analyzed in KOH and H2O2 medium at 298 K. The performance of the cathodes, in a single compartment, using a nickel plate as an anode was also investigated. The results showed that for the reduction reactions, electrodes developed with LSMMO have more significant catalytic activity than LSM after polarization, resulting in 32% higher current densities, lower electrical resistance after polarization, and a 21% increase in power density.

Highly Sensitive Humidity Sensor Based on Strontium-Doped Lanthanum Ferrite Nanofibers

Highly Sensitive Humidity Sensor Based on Strontium-Doped Lanthanum Ferrite Nanofibers

Highly Sensitive Humidity Sensor Based on Strontium-Doped Lanthanum Ferrite Nanofibers

Highly Sensitive Humidity Sensor Based on Strontium-Doped Lanthanum Ferrite Nanofibers

Investigating the effect of nano-structured magnetic particles lanthanum strontium manganite on perovskite solar cells

In this study, pure phase nanostructured strontium-doped lanthanum manganite, La0.75Sr0.25MnO3 (LSM), with a hexagonal structure was synthesized by sonochemical method. Then, XRD and SEM estimated the size of the LSM nanopowders. The results are exhibited that products synthesized in this method are compatible with particle size and morphology. Magnetic measurement was done by vibrating sample measurement (VSM) on LSM nanoparticles at room temperature. According to the results obtained from VSM displayed the saturation magnetization of LSM nanoparticles exhibited a maximum of 24.25 emu/g at room temperature. Then, the influence of LSM nanoparticle as an additive on the film morphology of CH3NH3PbI3 and the performance of perovskite solar cells was examined. We explore by using 5wt % of additive can increase the short current density (Jsc) from 14.45±0.55 to 18.29±0.38 mA/cm2 (~ 26.5 % enhancement) and power-conversion efficiency (PCE) from 8.33±0.40 to 12.41±0.35 (~ 49 % enhancement). Moreover, the morphology, and band gap of the new perovskite layer was improved.

Enhanced degradation of chloramphenicol through peroxymonosulfate and visible light over Z-scheme Photocatalysts: Synergetic performance and mechanism insights

Effective removal of antibiotics in the environment can be a demanding issue concerning the ecosystem and human health. Photocatalysis and peroxymonosulfate (PMS) oxidation have become important methods to effectively remove stubborn pollutants. In this work, by integrating these two technologies, an efficient system for degrading chloramphenicol (CAP) in water was proposed. The system was constructed by coupling strontium-doped lanthanum cobaltate (LSCO5) with chlorine-doped carbon nitride (CGCN). By doping, the increase of oxygen vacancy and the adjustment of bandgap were realized. Photoluminescence and electrochemical impedance experiments showed that the heterojunction can promote electron transfer and photogenerated carrier separation. Under the synergistic effect of PMS oxidation and photocatalysis, the prepared composite with an optimal loading of 40% LSCO5 can degrade 95.6% of CAP within 20 min. Degradation experiments on different pollutants proved the versatility of the catalytic system. The enhanced degradation mechanism of CAP was explored based on the assessment of the degradation efficiency of CAP, electron paramagnetic resonance (EPR), and quenching experiments. Through liquid chromatography-mass spectrometry (LC-MS) analysis, a possible route for CAP degradation was also proposed. This research provides some inspiration for the remediation of polluted water with perovskite-based catalyst under the synergistic effect of PMS and photocatalysis.

Investigating Effects of Operational Parameters on the Rate of Electrochemical Cleaning of Chromium Deposits on Strontium-Doped Lanthanum Manganite Cathodes in Solid Oxide Fuel Cells

Chromium poisoning of the cathode remains a significant obstacle to the long-term performance of solid oxide fuel cells. Previously, a quick, easy method was introduced that requires no material modifications, major thermal cycling, nor exposes the cell to any species it does not already encounter during operation. The method, electrochemical cleaning, reverses the electrochemical deposition reaction of chromium-containing species by applying a mild anodic bias. Chromium vapor species are formed, freeing active sites in the cathode. The method has been shown to completely recover cell performance via this current-voltage technique.The present work investigates the mechanism of electrochemical cleaning by assessing the effect of various operating parameters on the rate of chromium removal. Using a design of experiments method, eight cells were poisoned and then cleaned using differing combinations of the following cleaning parameters: cell temperature, air humidity, anodic current density, and fuel humidity. Regression analysis of two comparative metrics, cell performance via current voltage curves and post-test chromium content determined via Energy Dispersive Spectroscopy, demonstrated that cell temperature has the highest effect on the rate of chromium removal, followed by air humidity. A refined parameter space for future study is proposed for further optimization of the parameters. Previously, the electrochemical cleaning method was shown to be effective in the removal of Cr2O3 deposited species, but not Cr-Mn spinel deposits. The effects of operating parameters on the removal of the two different types of Cr deposits is discussed. An additional process for the removal of Cr-Mn spinel is demonstrated, which again makes use of the cell operating parameters. Together, the two methods present a facile, periodic process to greatly extend solid oxide fuel cell lifetime.

Micro-Tubular Solid Oxide Fuel Cells with One Closed-End Fabricated Via Dip-Coating and Co-Firing

Tubular solid oxide fuel cells (SOFCs) with one closed-end configuration have high tolerance of thermal cycling owing to the capability of expanding and shrinking freely in response to thermal stresses. Additionally, tubular cells with one closed-end have simple sealing requirements, and enable making the stacks with uniform temperature distribution. In this study, anode supported micro-tubular SOFCs with one closed-end were manufactured successfully by dip-coating and co-firing methods using carbon rods with round end as a template. A dense electrolyte layer was obtained at a co-firing temperature of 1400 °C, followed by cathode deposition and sintering. The prepared micro-tubular SOFCs comprised of Ni-yttria-stabilized zirconia (YSZ), Ni–scandia-stabilized zirconia (SSZ), strontium-doped lanthanum manganite (LSM)-SSZ, and LSM as the anode support, anode functional layer, electrolyte, cathode functional layer, and cathode current collector, respectively. The electrochemical performance and microstructure of fabricated closed-end micro-tubular SOFC was evaluated by electrochemical characterization and scanning electron microscopy. The developed dip-coating method is fast in turnaround time and enables fabricating the one closed-end tubes of various lengths and diameters by co-firing.

Micro-Tubular Solid Oxide Fuel Cells with One Closed-End Fabricated Via Dip-Coating and Co-Firing

The tubular solid oxide fuel cells (SOFCs) with one closed-end configuration have high thermal-cycling tolerance owing to the capability of expanding and shrinking freely in response to thermal stresses. The tubular cells with one closed-end have simple sealing requirements, and enable making the stacks with uniform temperature distribution. In this study, anode supported micro-tubular SOFCs with one closed-end were manufactured successfully by dip-coating and co-firing methods using carbon rods as a template. A dense electrolyte layer was obtained at a co-firing temperature of 1400°C, followed by cathode deposition and sintering. The prepared micro-tubular SOFCs were comprised of Ni-yttria-stabilized zirconia, Ni–scandia-stabilized zirconia (SSZ), SSZ, strontium-doped lanthanum manganite (LSM)-SSZ, and LSM as the anode support, anode functional layer, electrolyte, cathode functional layer, and cathode current collector, respectively. The developed dip-coating method is fast in turnaround time and enables fabricating the one closed-end tubes of various lengths and diameters by co-firing.

Investigating Effects of Operational Parameters on the Rate of Electrochemical Cleaning of Chromium Deposits on Strontium-Doped Lanthanum Manganite Cathodes in Solid Oxide Fuel Cells

Chromium poisoning of the cathode remains a significant obstacle to the stable long-term performance of solid oxide fuel cells. This study reports, a quick, in-situ mitigation method, called electrochemical cleaning. By applying a mild anodic bias, the electrochemical deposition reactions of chromium-containing species are reversed. Chromium vapor species are formed, freeing active electrochemical sites in the air electrode. An LSM/YSZ-based cell was exposed to Cr vapors at 800ºC and then subjected to electrochemical cleaning. Cell performance recovery was evidenced by current-voltage and EIS measurements. Chromium removal was verified using SEM and EDS analyses. The cyclability of the electrochemical cleaning was tested by repeated poisoning and cleaning of another cell. Investigation into the effect of cell operating parameters (current density and cell temperature) on the rate of cleaning is discussed.