Lanthanum Strontium Cobaltite Research Articles

Lanthanum strontium cobaltite-based perovskite as an electrocatalyst for zinc-air battery application

Developing a low-cost and highly efficient electrocatalyst for bifunctional oxygen electrocatalytic activity is crucial in the field of energy conversion and storage devices. In this study, we employed a doping strategy to finely tune the electronic structure of lanthanum strontium cobaltite-based perovskite. Furthermore, we introduce Mn, Ni, and Cu cations as dopants at the B-site of lanthanum strontium cobaltite, La0.5Sr0.5CoO3 (LSCO), to investigate oxygen electrocatalytic activity in alkaline electrolytes. Among the electrocatalysts we synthesized, La0.5Sr0.5Co0.8Ni0.2O3 (LSCNiO) exhibited the lowest OER overpotential (ηj=10) of 429 mV in 0.1 M KOH, surpassing LSCO by 71 mV and LCO by 204 mV, respectively. Additionally, LSCNiO demonstrated a positive potential of 0.68 V @ 1 mA cm−2 for ORR, which is 50 mV less for LSCO catalyst. The improved electrocatalytic activity was investigated using spectroscopic techniques, confirming the presence of oxygen vacancies and an elevated Co oxidation state. The synergistic interplay between Co and Ni cations enhanced the hybridization between Co/Ni 3d and O 2p bands, reducing energy barriers and improving oxygen reaction kinetics. Finally, LSCNiO oxide with a bifunctional index (ΔE) of 1.08 V is tested for zinc-air battery (ZAB) applications.

Overview of Approaches to Increase the Electrochemical Activity of Conventional Perovskite Air Electrodes.

The progressive research trends in the development of low-cost, commercially competitive solid oxide fuel cells with reduced operating temperatures are closely linked to the search for new functional materials as well as technologies to improve the properties of established materials traditionally used in high-temperature devices. Significant efforts are being made to improve air electrodes, which significantly contribute to the degradation of cell performance due to low oxygen reduction reaction kinetics at reduced temperatures. The present review summarizes the basic information on the methods to improve the electrochemical performance of conventional air electrodes with perovskite structure, such as lanthanum strontium manganite (LSM) and lanthanum strontium cobaltite ferrite (LSCF), to make them suitable for application in second generation electrochemical cells operating at medium and low temperatures. In addition, the information presented in this review may serve as a background for further implementation of developed electrode modification technologies involving novel, recently investigated electrode materials.

Evaluation and Upscaling of Impregnated La0.20Sr0.25Ca0.45TiO3 Fuel Electrodes for Solid Oxide Electrolysis Cells Under H2O, CO2 and Co-Electrolysis Conditions

Recent research into Rh and Ce0.80Gd0.20O1.90-impregnated La0.20Sr0.25Ca0.45TiO3 fuel electrodes for solid oxide fuel cells has demonstrated the high-stability of these material sets to a variety of harsh operating conditions at small scales (button cells with 1 cm2 active area), as well as full commercial scales (100 cm2 cells) in short stacks (5 cells) and full micro-combined heat and power systems (60 cells). In this work, the authors present a comprehensive evaluation of the ability of these novel titanate-based materials to function as fuel electrodes in solid oxide electrolysis cells (SOECs). Short-term and durability testing of button cell scale SOECs, under CO2 and steam electrolysis conditions, highlighted the limited stability of lanthanum strontium manganite-based air electrodes with lanthanum strontium cobaltite ferrite-based air electrodes offering improved degradation. Upscaling of this optimized cell chemistry to a 16 cm2 active area SOEC and testing under CO2, CO2/steam and steam electrolysis conditions demonstrated encouraging performance over a period of ~600 hours.

Synthesis and characterization of carbon nanotubes and activated carbon assisted sol-gel derived La0.6Sr0.4CoO3-δ material

A pure perovskite-type oxide ceramic nanomaterial can be produced at a lower processing temperature than 1000 °C via sol-gel method. However, it is influenced by the nature of chemical agents such as chelating agent, surfactant and dispersant added during the synthesis process. Among them, dispersant is regarded as an important chemical agent as it can prevent the formation of hard agglomerated particles which is the main drawback of sol-gel method. In the present work, ceramic powder of lanthanum strontium cobaltite, La0.6Sr0.4CoO3-δ (LSCO) was prepared via sol-gel method with the aid of carbon nanotubes (CNTs) and activated carbon (AC) as dispersant. The prepared powder was characterized by thermal gravimetric analyser (TGA), X-ray diffractometer (XRD) and scanning electron microscope (SEM) equipped with energy dispersive X-ray (EDX) spectrometer to evaluate its thermal decomposition, structural and microstructure properties, respectively. Thermal decomposition of the as-synthesized CNTs-based and AC-based powders completed at temperature 750 °C and pure perovskite phase of LSCO was formed at temperature 900 °C. Both CNTs-based and AC-based calcined powders consist of homogeneous and almost identical shape of particles. However, the CNTs-based calcined powder has higher agglomeration index value than the AC-based calcined powder as revealed in SEM images.

Investigation of Heat Distribution in SOC-Stacks By Multiphysical Modeling

In the scope of clean energy, the solid oxide cell (SOC) offers a promising solution for different applications. The electrolyte, the air electrode and the fuel electrode of an SOC are typically based on yttrium stabilized zirconia (YSZ), lanthanum strontium cobaltite (LSC) or manganite (LSM) and nickel cermet, respectively. It typically operates in a temperature range of 600 – 1000 oC and can be operated as a fuel cell (SOFC), an electrolysis cell (SOEC) or reversibly (rSOC).An SOC-stacks consists of several repeating units, each of which is assembled by various components. Among them, the sealants are important to maintain the reliability and long-term operations of a stack. Several issues lead to high stress in the sealants, including the mechanical load, mismatch of thermal expansion coefficients, and thermal gradients 1. It was indicated that a small temperature gradient near the manifolds results in excessively high tensile stress. This may lead to glass ceramics sealing failure, which is critical in SOC designs 2. Therefore, the authors carry out the elastic stress simulations in an operating SOC-stack due to non-uniform temperature distributions.A previously introduced CFD model 3 is further developed to address coupled chemical and electrochemical reactions in rSOC-stacks. This model has been implemented in the open-source library, OpenFOAM. It considers the major multiphysical phenomena e.g. heat, mass, momentum and charge transport as well as heat radiation and electrochemical reactions and employs a volume-averaged approach 4. The computational requirements can be greatly reduced, which offers the possibility to simulate large stacks in reduced computing time. The temperature distributions derived from the stack simulation are used as inputs for thermal stress analysis, by mapping the interconnect temperatures to the detailed repeating unit. An open-source, finite element method (FEM) based software, Calculix, is applied to simulate the stress distributions. It is assumed all layers are tightly connected without slipping.The SOC-stack design considered in the multiphysical simulation as well as the FEM stress analysis is an in-house design, Mark-F20. It consists of 18 repeating units, each with an active area of approximately 320 cm2. The stack operates in the furnace condition, at a temperature of 700 oC, with CH4 mixture being supplied to the anode in the SOFC-mode (i=0.5 A/cm², U=0.8 V). The flow is in a counter-flow regime. A comparison of temperature distributions in interconnect is conducted between simulation and experiment. A maximum deviation of 10 K can be observed near the fuel inlet. It is acceptable providing the overall temperature variations of 80 K and the uncertainties in the measurements. This low-temperature zone results from the fast endothermic methane steam reforming reaction. The zone near the fuel outlet is cooled down by the inlet airflow on the cathode side. The stress-free temperature is 800 oC. It can be found that the maximum stress appears around the fuel inlet manifold with a magnitude of 100 MPa. The stress is also large near the air inlet manifold with a magnitude of 70 MPa. These areas show higher possibilities of mechanical failure.Consequentially, the stack model that has been developed enables to investigate the heat distribution in SOC-stacks. By comparing temperature distribution and the IV-curve predicted by the model with experimental measurements, good agreements were found.In the future, the sealant failure will be investigated 2 and attention has to be paid to future stack designs. References(1) Blum, L.; Groß, S. M.; Malzbender, J.; Pabst, U.; Peksen, M.; Peters, R.; Vinke, I. C. Investigation of Solid Oxide Fuel Cell Sealing Behavior under Stack Relevant Conditions at Forschungszentrum Jülich. Journal of Power Sources 2011, 196 (17), 7175–7181.(2) Bremm, S.; Dölling, S.; Becker, W.; Blum, L.; Peters, Ro.; Malzbender, J.; Stolten, D. A Methodological Contribution to Failure Prediction of Glass Ceramics Sealings in High-Temperature Solid Oxide Fuel Cell Stacks. Journal of Power Sources 2021, 507, 230301.(3) Zhang, S.; Peters, R.; Varghese, B. A.; Deja, R.; Kruse, N.; Beale, S. B.; Blum, L.; Peters, R. Modeling of Reversible Solid Oxide Cell Stacks with an Open-Source Library. ECS Trans. 2021, 103 (1), 569.(4) Beale, S. B.; Zhubrin, S. V. A Distributed Resistance Analogy for Solid Oxide Fuel Cells. Numerical Heat Transfer, Part B: Fundamentals 2005, 47, 573–591. Figure 1

Flash Light Sintered SOFC Cathode Functional Layer through Electrostatic Spray Deposition

Solid oxide fuel cells(SOFCs), which are attracting attention as an eco-friendly power generation system, are being actively studied due to their fuel flexibility and high efficiency. Since the charge carriers are oxygen ions and have to pass through the solid oxide electrolyte, they require a higher operating temperature (~900 oC) than other fuel cells. To overcome the disadvantages of high-temperature operation, research is being conducted to lower the operating temperature of the SOFCs. In particular, in order to minimize performance degradation even at low operating temperatures, research is being conducted to fabricate cell components as thin films or to apply electrodes with high catalytic activity and large reaction areas.Among the methods of manufacturing thin films, the deposition method using chemical solution deposition(CSD) has the advantage of being cost effective and easily controllable compared to the vacuum deposition method. Electrostatic spray deposition(ESD), one of the CSD deposition methods, is simple to set-up and a variety of compounds can easily be made by controlling the proportions of the precursors. However, a characteristic of the CSD method is that a post heat treatment process is required to obtain desired properties, which consumes a lot of time and cost during the entire process. To solve this problem, processes such as rapid thermal annealing, microwave, and excimer laser ablation are being studied, but these processes have limitations in that they damage the substrate, have a long cooling time, and have a small sintering area. [1, 2] On the other hand, the flash light sintering method using a xenon lamp can perform a post-heat treatment process quickly at room temperature and atmospheric pressure using intense pulsed light, and has the advantage of minimizing damage to the substrate and being applicable to a large area. [3, 4]In this study, the cathode functional layer, which is closely related to the performance of SOFC, was fabricated using the ESD method, and the flash light sintering method was applied for the post-heat treatment process. By applying the flash light sintering method, the heat treatment process, which used to take tens of hours, was shortened to just a few seconds. The sintering behavior of the film produced by flash light sintering was confirmed by comparing the microstructure and crystallinity. In addition, it was confirmed that the film manufactured by flash light sintering worked successfully by comparing the performance with the cell manufactured by the conventional thermal sintering method. Reference [1] R. Bayati et al., "Modification of Properties of Yttria Stabilized Zirconia Epitaxial Thin Films by Excimer Laser Annealing," (in English), Acs Applied Materials & Interfaces, vol. 6, no. 24, pp. 22316-22325, Dec 24 2014.[2] H. S. Hao, L. H. Xu, Y. Huang, X. M. Zhang, and Z. P. Xie, "Kinetics mechanism of microwave sintering in ceramic materials," (in English), Science in China Series E-Technological Sciences, vol. 52, no. 9, pp. 2727-2731, Sep 2009.[3] J. S. Park, D. J. Kim, W. H. Chung, Y. Lim, H. S. Kim, and Y. B. Kim, "Rapid, cool sintering of wet processed yttria-stabilized zirconia ceramic electrolyte thin films," (in English), Scientific Reports, vol. 7, Sep 29 2017.[4] J. S. Park, H. Lee, S. Heo, and Y. B. Kim, "Heater-assisted intense pulsed light irradiation for lanthanum strontium cobaltite thin film electrode fabrication," (in English), Thin Solid Films, vol. 697, Mar 1 2020.

Superior dual mode electrochemical sensing of NH3 using Ni2+ doped CuO anode with lanthanum gallate based electrolyte

Lanthanum gallate based electrochemical sensor was investigated in amperometric and potentiometric modes. A constant bias voltage of + 1 V was applied at CuO based electrode with respect to a fixed lanthanum strontium cobaltite (LSC55) electrode for detecting 3–40 ppm NH3 in base gas (5% O2 + N2) from 300 ℃ to 650 ℃ with the aim for exhaust gas application. CuO electrode composition with Ni2+ doping was studied and sensor with 2 mol% Ni2+ doped CuO exhibited highest sensitivity of 2124 µA/decade and 338 mV/decade at 550 ℃ in amperometric and potentiometric modes respectively. Using electron paramagnetic resonance (EPR) spectroscopy, the reason for the highest sensing performance due to the formation of efficient active sites for this specific doping of CuO was ascertained. Incidentally, all the sensors were found reproducible in sensing, fast in operation. The electrochemical sensor could detect concentration of NH3 as low as 3 ppm even at temperature 300 ℃ because of high ionic conductivity of the electrolyte and the electrode performances. Influence of biasing, preferential electrochemical reactions at the electrode-electrolyte interfaces and oxygen pumping current through the electrolyte confirmed the mechanism of sensing. High selectivity for ammonia detection with respect to others coexisting gases was observed. High sensitivity in both the sensing modes with minimum sensing down to 3 ppm NH3 makes the developed sensor a promising candidate for exhaust gas application.

Lanthanum strontium cobaltite as interconnect in oxide thermoelectric generators

Issues related to use of metallic interconnects in oxide thermoelectric generators (TEGs) need to be addressed to secure performance and durability. Metal interconnects suffer from high cost of noble metals or chemical instability and contact resistance of non-noble metals, arising from oxidation, evaporation, and delamination in the oxidising conditions of ambient air at high operating temperatures. This work introduces the use of a stable and highly conducting ceramic oxide, in our case p-type lanthanum strontium cobaltite (La0.6Sr0.4CoO3, LSC) as interconnect. We verified the thermochemical stability of LSC in contact with p-type Ni0.98Li0.02O (Li–NiO) and n-type Zn0.98Al0.02O (Al–ZnO) and examined the electrical characteristics. An area specific contact resistance (ASRc) of ∼1800 Ω cm2 for a direct p-n junction was reduced to ∼400 mΩ cm2 for a p-LSC-n junction at a temperature of 300 °C, validating the concept. The use of a screen-printed LSC/Al–ZnO composite as a thin interconnect layer was found to decrease the contact resistance of the junction further to ∼260 mΩ cm2 at 300 °C, attributed to increased effective area of the LSC/Al–ZnO p-n junction.

Solid-state compatibility of Ca:LaNbO4 with perovskite cathodes: Evidences from X-ray microspectroscopy

The solid-state compatibility between calcium-doped lanthanum niobate and three perovskite cathode materials was investigated using two X-ray microbeam techniques, micro X-ray fluorescence and micro X-ray absorption spectroscopy. The cathode powders (lanthanum strontium ferrite, either cobalt or copper-doped, and lanthanum strontium cobaltite) in contact with the dense electrolyte pellet were annealed at 1150°C for 12–144 h to simulate the effect of thermal stresses due to fabrication and long-term operation. As a result, several interdiffusion phenomena were then observed on the bilayer cross-sections: in particular, the chemical state and coordination environment of calcium, iron, niobium and lanthanum were probed with space-resolved X-ray absorption spectroscopy. The ab initio modeling of the near-edge X-ray absorption spectra reveal that the cation interdiffusion is facilitated by the structural flexibility of the perovskite structure, which is able to accommodate a variety of foreign cations in different oxidation states. Limited stability at high-temperatures was found for all candidate perovskite compositions in contact with lanthanum niobate.

Lanthanum Strontium Cobaltite-Alumina Fiber Composite Contact Material for Solid Oxide Fuel Cells

Lanthanum strontium cobaltite (LSCo) is considered a good candidate as cathode contact materials for SOFC applications, due to its high electrical conductivity as compared to the standard LSM materials. However, it suffers very poor thermal cycle stability because large mismatch in CTE. To overcome the large residual stress, we proposed to use strong and short alumina fiber to enforcement the LSCo matrix. Alumina in vol% from 2.5 to 20% were formulated and prepared for sintering study, thermal expansion coefficient measurement, phase characterization, bulk strength, and contact strength evaluation before and after 10 deep thermal cycles. Results showed the presence of rigid alumina fiber did retard the densification of LSCo matrix substantially at high alumina content. Bulk strength showed increasing trend at low alumina content but decreased at high alumina v%, likely due to severe retardation in densifications. Contact strength on 1”x1” bilayer showed the strong bonding at low alumina v% while good thermal cycle stability was observed. The candidate composite was further tested in a stack fixture using 2”x2” cell. Results of impedance versus cycling and microstructure and fracture analysis will be discussed to assess the validity of fiber reinforced LSCo as contact material.

Cation Diffusion in Non-Stoichiometric (La, Sr)MnO3/CeO2 Nano-Composite Cathode

Co-sintering of stacks or cells containing electrodes, electrolytes, and separators is essential fabrication technology to improve power density per unit volume significantly. Generally, cathode materials have low heat-resistant temperatures, and they are easily decomposed or degraded by sintering at a high temperature. (La0.8Sr0.2) MnO3 (LSM) shows relatively high resistance and preferable low-reactivity with fluorite electrolytes during sintering at a high temperature. But it shows lower cathodic properties than lanthanum strontium cobaltite or lanthanum strontium cobalt ferrite because of poor oxygen diffusion. Thus, we have investigated LSM/ceria nanocomposite to improve oxygen diffusion.Nanocomposite precursor powder containing LSM and ceria was synthesized by glycine method. The composite ratio of LSM and ceria was fixed at 9:1 (molar ratio). The dense composite compact was obtained by sintering the powder at 1200oC for 5 h in air, and fine ceria particles were homogeneously dispersed with LSM. Electrical conductivity and oxygen diffusion coefficient were estimated with these dense composites. Oxygen diffusion coefficients were estimated by electrical conductivity relaxation method. The amount of cation dissolved in ceria was investigated from XRD peak shifts. The defect of La or Sr in LSM formed by sintering with ceria was estimated with magnetic properties of LSM and LSM/ceria nanocomposite. The defect was also investigated using the relationship between activation energy and composition of a-site defect LSM or La-defect LSM.LSM showed a low oxygen diffusion coefficient, and the coefficient of LSM/ceria nanocomposite was much improved even though ceria composite ratio is 10%. However, LSM/ceria composite showed much lower conductivity than LSM since a-site cation of LSM, La or Sr, may be easily diffused into ceria. XRD peaks derived from only ceria were shifted toward lower angle for LSM/ceria nanocomposite prepared under various sintering conditions. The shift revealed that 2-5% La in LSM was diffused into ceria, assuming that only La is diffused. Diffusion of La into ceria increases in oxide ionic conductivity and the diffusion would benefit the composite's cathodic properties in terms of oxygen diffusion. However, if the diffusion would bring about La defect LSM and deviations from the optimum composition, the diffusion would be detrimental in terms of electrical conductivity.Then we investigated the effects of the diffusion on the defect structure of LSM in LSM/ceria nanocomposite by magnetic properties and electrical conductivities. Assuming that only La of LSM was diffused into ceria, the loss amount of La from LSM was estimated with magnetic phase transition temperatures for LSM and LSM/ceria nanocomposite. The temperatures were measured by SQUID. The overall loss amount of La from LSM was increased according to solid solution of La in ceria. But, the loss amount was slightly different from the solution amount to ceria.The ionic radius of Sr2+ is similar to that of La3+. Dissolution of Sr in ceria also leads to XRD peaks shift toward lower angle as well as that of La. Then, we investigate whether the loss from LSM was derived from only La (La-defect LSM) or both La and Sr ( a-site-defect LSM). La-defect and a-site-defect LSM dense ceramics with various defect concentrations were prepared by glycine method. Activation energy of these LSM ceramics was estimated from the temperature dependence of electrical conductivity measured in air. That of La-defect LSM was monotonically decreased with increasing defect concentration. A-site-defect LSM showed no significant change in activation energy within the defect concentration less than 8%. The relationship between activation energy of LSM/ceria nanocomposite and the defect concentration of LSM was measured using various sintering conditions. The relationship showed the activation energy of LSM/ceria was almost independent of the defect concentration. Therefore, Sr would simultaneously diffuse from LSM to ceria during sintering LSM/ceria nanocomposite. Electrical degradation of LSM/ceria nanocomposite would be derived from Sr defect of LSM as well as La.

Performance and Processes of Pure CO2 Electrolysis in Solid Oxide Cells

In solid oxide electrolysis cells (SOECs) carbon dioxide (CO2) is converted to carbon monoxide (CO). In the chemical industry CO is an important reactant to produce base chemicals such as acetic or formic acid or fine chemicals produced by carbonylation processes. CO is also used in the reduction of oxides to metals. Conventional processes for CO production are based on fossil resources such as coal or natural gas. CO2 electrolysis presents a sustainable method to utilize renewable energy for CO production and additionally transforms the greenhouse gas CO2 into a resource.Carbon dioxide is already used and investigated in the co-electrolysis process where it is converted alongside steam to produce syngas, a mixture of hydrogen and carbon monoxide. However, the analysis of pure CO2 electrolysis for CO production hasn’t been investigated in detail. Some studies report alternative materials or first degradation results. In this contribution the CO2 electrolysis is discussed in-depth from an electrochemical point of view. A detailed analysis by current-voltage characteristics (IV curves) and electrochemical impedance spectroscopy (EIS) was performed on commercially available cells by Elcogen consisting of a Nickel/ 8 mol % Yttrium-Stabilized Zirconia (8YSZ) cermet fuel electrode, a 8YSZ electrolyte, a Cerium Gadolinium Oxide barrier layer and a Lanthanum Strontium Cobaltite air electrode. IV curves and EIS spectra were measured at varied CO2/CO ratios, temperatures, flow rates and current densities.The results show that with increasing CO2/CO ratio the total area specific resistance (ASR) increases at open circuit voltage and decreases under load (Figure 1). A similar decrease of resistance is seen for increasing flow rates. The main resistance contribution determined from impedance analysis comes from diffusion/concentration losses[1]. The analysis by impedance spectroscopy provides information on the underlying processes and is not only of relevance for understanding pure CO2 electrolysis but also for understanding the role of CO2 reduction during co-electrolysis. Figure caption: Figure 1: ASR, |i|1.4 V and OCV for varied CO2/CO ratios at 800 °C[1]. 1Two values are given due to a hysteresis. The first value represents the forward scan and the second value represents the backward scan of the IV curve. Literature [1] S. Foit, L. Dittrich, T. Duyster, I. Vinke, R.-A. Eichel, Haart, L. G. J. de, Processes 2020, 8, 1390. Figure 1

Understanding High-Temperature Electrolysis

Electrolysis is the technology, which provides the key for sector coupling. It enables the conversion of renewable energy to material value generation. Therefore, it is of utmost importance, that the energy is used in the most efficient way. High-temperature electrolysis on solid oxide cells provides high efficiency combined with the possibility to convert both water (H2O) and carbon dioxide (CO2) to hydrogen (H2) and carbon monoxide (CO)[1].For a purposive improvement of the efficiency of the high-temperature electrolysis, a precise understanding of the on-going processes is needed[2]. Both the electrochemical and the procedural processes can have a significant impact on the performance, lifetime and overall effectiveness of the conversions taking place[3]. Some of the outcomes of changing operation parameters have been discussed before, although focusing on specific topics within the field. Therefore, a comprehensive sweep of parameters has to be conducted and results and findings have to be analyzed in full detail[3-6].In this contribution, we show the summary and conclusions of multiple investigations of the high-temperature electrolysis. A series of detailed analysis has been performed using current-voltage characteristics (IV curves) and electrochemical impedance spectroscopy (EIS). The sets of experiments were conducted using commercially available cells (Elcogen) consisting of a Nickel/ 8 mol % Yttrium-Stabilized Zirconia (8YSZ) cermet fuel electrode, an 8YSZ electrolyte, a Cerium Gadolinium Oxide barrier layer and a Lanthanum Strontium Cobaltite air electrode. The variation of parameters included feed gas compositions ranging from pure water electrolysis to pure carbon dioxide electrolysis and co-electrolysis in between, temperature range of 650 °C to 900 °C, flow rates with various space-velocities, current densities from OCV up to over 2 A·cm2 and measurement times up to 500 h. In parallel a full-scale model was developed starting from fundamental thermodynamics over applied kinetics using Comsol software, in order to compare the experimental results and evaluation with the simulation results. As a first result, we are able to show a solution to the discussion of the role and impact of the direct electrochemical conversion of carbon dioxide during co-electrolysis. This is a first essential step for the understanding of high-temperature electrolysis in general. Foit, S.R.; Vinke, I.C.; de Haart, L.G.J.; Eichel, R.-A. Power-to-syngas: An enabling technology for the transition of the energy system? Angew. Chem. Int. Ed. 2017, 56, 5402-5411.Foit, S.R.; Dittrich, L.; Vibhu, V.; Vinke, I.C.; Eichel, R.-A.; de Haart, L.G.J. Co-electrolysis, quo vadis? ECS Transactions 2017, 78, 3139-3147.Dittrich, L.; Nohl, M.; Theuer, T.; Foit, S.; Vinke, I.C.; de Haart, L.G.J.; Eichel, R.-A. Co-electrolysis – a sustainable technology for syngas production. Chem. Ing. Tech. 2018, 90, 1158-1159.Theuer, T.; Schäfer, D.; Dittrich, L.; Nohl, M.; Foit, S.; Blum, L.; Eichel, R.-A.; de Haart, L.G.J. Sustainable syngas production by high-temperature co-electrolysis. Chem. Ing. Tech. 2020, 92, 40-44.Foit, S.; Dittrich, L.; Duyster, T.; Vinke, I.; Eichel, R.-A.; de Haart, L.G.J. Direct solid oxide electrolysis of carbon dioxide: Analysis of performance and processes. Processes 2020, 8, 1390.Dittrich, L.; Nohl, M.; Jaekel, E.E.; Foit, S.; de Haart, L.G.J.; Eichel, R.-A. High-temperature co-electrolysis: A versatile method to sustainably produce tailored syngas compositions. J. Electrochem. Soc. 2019, 166, F971-F975. Figure 1

Gold particle effect on high temperature oxygen reduction reaction via lanthanum strontium cobaltite ferrite electrocatalyst

Gold is generally considered to be inert for electrochemical reactions in solid oxide fuel cells (SOFCs). It is thus used as the standard current collector to characterize the catalytic activity of various cathode materials including the state-of-the-art lanthanum strontium cobalt iron oxide (LSCF). This work shows that gold is not inert but active for oxygen reduction reaction (ORR) via LSCF. Electrical conductivity relaxation measurement shows that scattered gold particles on LSCF surface can greatly increase the ORR rate. Gold improves the chemical oxygen surface exchange coefficient by a factor up to 27.5. The improvement is much high at reduced temperature from 800 to 650 °C. In addition, gold particles with smaller size show better performance in enhancing the ORR activity.

Designing perovskite catalysts for controlled active-site exsolution in the microwave dry reforming of methane

The dry reforming of methane (DRM) is a promising process for generating syngas (CO + H2) while consuming CO2, but industrial applications have been limited due to the high temperatures required to prevent coke formation. Microwave-assisted DRM (MW-DRM) is a promising approach to enable high temperature reactions because it can utilize excess renewable electrons to rapidly and selectively heat the catalyst bed without wasting time and energy heating the entire reactor. Here we demonstrate the MW-DRM reaction by modifying lanthanum strontium cobaltite (LSC) to serve as both microwave absorber and catalyst. Catalyst doping studies revealed the addition of oxophilic transition metals prevented over-reduction and stabilized the perovskitic phases under reaction conditions. In situ, synchrotron-based x-ray diffraction revealed the catalyst becomes active once metallic cobalt forms on a retained perovskitic support. The best performing Mn doped LSC catalyst showed 80–90 % single-pass conversions, stable operation for over 10 h, and easy microwave regeneration.

Nano-Ceramic Cathodes via Co-sputtering of Gd–Ce Alloy and Lanthanum Strontium Cobaltite for Low-Temperature Thin-Film Solid Oxide Fuel Cells

We report the electrochemical performance and structural characteristics of porous nanostructured ceramic cathodes for thin-film solid oxide fuel cells (TF-SOFCs) based on yttria-stabilized zirconi...

Lanthanum strontium cobaltite-infiltrated lanthanum strontium cobalt ferrite cathodes fabricated by inkjet printing for high-performance solid oxide fuel cells

Abstract In this study, lanthanum strontium cobalt ferrite cathodes surface-treated with lanthanum strontium cobaltite nanoparticles are synthesized using inkjet printing and their performances are evaluated using intermediate-temperature solid oxide fuel cells. The porous lanthanum strontium cobalt ferrite cathode of an anode-support solid oxide fuel cell is prepared under optimized inkjet printing conditions. The surface treatment is performed by infiltrating a lanthanum strontium cobaltite ink followed by calcination. The lanthanum strontium cobalt ferrite cathode is evenly surface-covered with lanthanum strontium cobaltite nanoparticles, confirming the effectiveness of the inkjet printing for the cathode surface modification. The fuel cell performances are evaluated in the intermediate temperature range of 550–650 °C. The power is significantly improved even with a small addition of the surface lanthanum strontium cobaltite; the enhancement factor reaches the value of five. An electrochemical impedance analysis confirms that the enhanced fuel cell performance is attributed to the reduced polarization impedance, significantly activating the surface catalysis. The addition of lanthanum strontium cobaltite retained the stability of the lanthanum strontium cobalt ferrite cell. However, an excessive amount of lanthanum strontium cobaltite significantly reduces the cell performance.

Thermal decomposition, phase formation and microstructure analysis of surfactant assisted sol-gel derived La0.6Sr0.4CoO3-δ material

A single-phase of perovskite-type oxide material can be prepared at a processing temperature relatively lower than 1000 °C through a sol-gel method. However, it is affected by the nature of chemical additives employed during the synthesis process. In the present work, sol-gel derived lanthanum strontium cobaltite, La0.6Sr0.4CoO3-δ (LSC64) material is prepared using various non-ionic surfactants namely polyoxyethylene (10) oleyl ether (Brij-97), polyoxyethylene octyl phenyl ether (Triton-X-100) and polyoxyethylene (20) sorbitan monooleate (Tween-80). The prepared powders of the LSC material is subsequently subjected to the thermal decomposition, phase formation and microstructure analysis by a thermal gravimetric analyzer, an X-ray diffractometer and a scanning electron microscope (SEM), respectively. The as-synthesized powders are calcined at different temperatures based on the thermal gravimetric analysis results. X-ray diffractometer results reveal that all of the calcined powders consist of more than 90 % perovskite phase of LSC64 and other secondary phases such as cobalt oxide, lanthanum oxide and strontium carbonate. The Brij-97-based and Tween-80-based calcined powders have morphology of typical clump-like network structure, while the Triton-X-100-based calcined powder has morphology of flake-like network structure.

Heater-assisted intense pulsed light irradiation for lanthanum strontium cobaltite thin film electrode fabrication

This study describes the bottom-heater-assisted flash light irradiation method for fabrication of lanthanum strontium cobaltite (La0.6Sr0.4CoO3−δ, LSCO) thin films. Unlike the conventional sintering process, flash light irradiation proceeds instantly under ambient conditions. Since the flash light irradiation process involves the photothermal effect, heat energy supplied by a bottom heater can compensate for decreased irradiation energy. The substrate temperature was varied from room temperature to 200 °C and 300 °C, and the radiation energy requirement for obtaining an optimized LSCO film was decreased with increasing temperature. In addition, the instantaneous temperature difference due to highly intense energy between the top surface and the substrate can be relieved. With the innovative sintering system, an electrolyte-supported solid oxide fuel cell could be fabricated by the flash light irradiation method, and electrochemical characterization of the fuel cells was conducted.

80,000 current on/off cycles in a one year long steam electrolysis test with a solid oxide cell

The current ON/OFF switching of a solid oxide electrolysis cell is treated as elementary step for power variation in a steam electrolyser system. If the cell voltage in the ON mode is adjusted to the thermal neutral voltage, heat generation remains zero in both modes, which largely facilitates the thermal management. To verify whether the cells withstand the switching, an electrolysis durability test with an electrolyte supported solid oxide cell was performed during one year at about 850 °C. The cell consisted of a 3YSZ electrolyte, CGO diffusion-barrier/adhesion layers, a lanthanum strontium cobaltite ferrite (LSCF) oxygen electrode, and a nickel/gadolinia-doped ceria (Ni/GDC) steam/hydrogen electrode. The test included two operation blocks with each 40,000 cycles of 2 min duration and a current density of −0.7 Acm−2 in the ON mode (−0.07 Acm−2 in OFF mode), as well as steady-state ON periods with 5800 h duration. Voltage degradation was 5 mV/1000 h (0.4%/1000 h) and the increase in the area specific resistance 7 mΩcm2/1000 h, without notable dependence on current cycling. Impedance spectroscopic results were in agreement with the only small switching transients seen in the cell voltage; moreover, they confirmed a dominating ohmic degradation together with minor contributions from gas conversion and reaction, respectively. No electrode delamination was detectable after scheduled test completion.