Solid Oxide Electrochemical Cells Research Articles

Dense La0.3Sr0.7TiO3 interconnect sintered in air atmosphere at a reduced temperature with improved conductivity for solid oxide electrochemical cells

La-doped SrTiO3 (LaxSr1-xTiO3, LST), as the promising ceramic-based interconnect material, usually needs to be sintered in reductive atmosphere at a temperature ≥ 1450 °C, such sintering condition is not friendly to cell fabrication and application. To reduce the sintering temperature of air-sintered LST, seven sintering additives, Bi2O3, Fe2O3, Li2O, MnO2, NiO, V2O5, and Co3O4, are added to the LST in this work. The results show that only Co3O4 is conductive to remarkable sintering at the temperatures of 1250 °C. The relative density of LST-3%Co3O4 reaches 92%, while that of the pure LST is only 48%. Moreover, the conductivity of LST-3%Co3O4 achieves 8.2S/cm at 800 °C in humidified hydrogen, which exceed 5.5 times that of the pure LST. Interestingly, LST-3%Co3O4 exhibits an average TEC of 11.5×10-6K-1 between 400 and 900 °C, which is very close to that of other components of SOCs.

Cross-Validation of the Remarkably High Surface Oxygen Exchange Kinetics of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ: A Combined Thin-Film Mass Relaxation and Bulk Electrical Conductivity Relaxation Study.

In this work, we measure the oxygen kinetic properties of double perovskite PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), a material widely used as the air electrode in solid oxide electrochemical cells, by mass relaxation (MR) and electrical conductivity relaxation (ECR) experiments. MR studies are carried out using thin films deposited on a gallium phosphate piezocrystal microbalance, and ECR studies are performed using a bulk bar sample with 97% theoretical density. Measurements are performed at 600 °C over the temperature oxygen partial pressure range from 10-4 to 0.21 atm. Despite the differences in experimental formats and surface microstructural features, the ks values extracted from the two methods are found to be in good agreement with one another. The rate constant is found to increase with oxygen partial pressure with a power law dependence, rising from 1.0 × 10-6 cm/s at 3.2 × 10-4 atm to 1.2 × 10-4 cm/s at 0.24 atm, as averaged over the oxidation and reduction directions. The rates in the oxidation direction are observed to be slightly higher than those in the reduction direction for a given pair of pO2 values, suggesting that the final pO2 value controls the overall relaxation behavior. The power law exponent describing the dependence of ks on pO2 is found to be 0.74 ± 0.01. The ECR study of the bulk sample reveals that even with a diffusion length of 1.8 mm, the relaxation process is largely free of diffusion limitations, indicating that PBSCF has the high bulk transport properties required for a double-phase boundary oxidation/reduction pathway.

The emerging Sr2FeMoO6-based electrocatalysts for solid oxide electrochemical cell: synthesis, modulation and applications

Solid oxide cells (SOCs) are regarded as a promising energy technology due to their large current density, diverse range of fuels, and high energy conversion efficiency. The double perovskite Sr2FeMoO6 (SFM) has attracted considerable attention for SOCs due to its tunable structure with superior performance of high conductivity, excellent thermal stability, and remarkable carbon deposition resistance in a reducing atmosphere. However, the electrocatalytic activity of SFM is considerably lower than that of commercial Ni-based SOC electrodes. A timely summary of the synthesis, modulation, and application of SFM perovskites is of great significance for its further development for SOCs. In this review, the methods employed in the preparation of SFM electrocatalysts are introduced first. Then, the advancements in the application of different SFM-based electrocatalysts in the field of SOCs are reviewed, and the research progress in the in situ exsolution of SFM-based electrocatalysts through ion regulation is assessed. Finally, the future issues associated with SFM-based electrocatalysts are addressed in the realm of electrocatalysis, to advance their application.

Mars In Situ Resource Utilization (ISRU) with Focus on Atmospheric Processing for Near-Term Application—A Historical Review and Appraisal

The inspirational paper by Ash, Dowler, and Varsi in 1978, proposing to utilize in situ resources on Mars (ISRU) rather than bringing them from Earth, originated the field of Mars ISRU that has been the subject of research ever since. In this paper, we reviewed significant research reported on Mars ISRU since 1978 and reported briefly on accomplishments. We found that prior to 2014, progress on small tasks was sporadic and intermittent, always at low Technology Readiness Level (TRL). In 2014, the National Aeronautics and Space Administration (NASA) took a bold, imaginative, unprecedented step to fund a major project in Mars ISRU: the so-called “MOXIE” (Mars Oxygen In Situ Experiment), in which an oxygen production plant based on solid oxide electrolysis (SOEC) was developed, and finally demonstrated on Mars in 2022 and 2023. While MOXIE leaves behind it a wealth of accomplishments, there remains the need to close remaining gaps with additional laboratory and field work. Solid-oxide electrochemical cell (SOEC) technology has become a major area of worldwide investment for terrestrial energy and CO2 control. There is a very strong overlap between this terrestrial technology and Mars ISRU. NASA has already leveraged the terrestrial development work via MOXIE. NASA can leverage further advances with a comparatively small investment beyond 2023. Because NASA is engaged in a major program to return humans to the Moon, NASA’s focus is on lunar ISRU. Unfortunately, the mission impact and return on investment for lunar ISRU does not compare to that for Mars ISRU. NASA’s concept for Mars ISRU is futuristic, involving autonomous mining, transporting, and processing large amounts of Mars regolith. This might well occur long after initial human landings which could better profit in the near-term from MOXIE technology. By continuing further development of SOEC technology beyond MOXIE, while leveraging large investments in terrestrial applications, NASA can develop the Mars ISRU appropriate to nearer term human missions at modest investment. The goal of this paper is to place the relatively mature MOXIE technology advance and solid oxide electrolysis in general in perspective to the historical evolution of low TRL Mars ISRU technology.

(Invited) Ruddlesden-Popper Oxides As Bi-Functional Oxygen Electrodes

Incorporating more renewables into our energy mix is a major challenge that confronts our transition to a carbon free economy. Solid oxide electrochemical cells when operated alternately in fuel cell and electrolysis modes, enable the incorporation and integration of far greater amounts of solar and wind energy into our power grid. As islanded systems, they can also function as distributed generation systems thereby decreasing our reliance on the power grid. In this talk, we present a recent survey of results on rSOCs based on rare earth nickelate – rare-earth doped ceria composite oxygen electrodes that exhibit excellent cycling behavior when operated alternately in solid oxide fuel cell (SOFC) and solid oxide electrochemical cell (SOEC) modes of operation. The degradation in such cells is significantly mitigated by mode-switching operation when compared to operating in single mode operation in electrolysis mode. By comparing distributed relaxation times (DRT) analysis of impedance spectra obtained from single-mode (electrolysis) operated cells, and cells operated in switched-modes, we obtain clues into cell degradation mechanisms.

(Digital Only Presentation) Effects of Ink Solvent on the Screen-Printing Fabrication and Morphology of LSM-YSZ Thin Films Deposited on YSZ Substrate for Solid Oxide Electrochemical Cells

Screen-printing is a cheap and easy thin film deposition technique utilized in energy devices fabrication, specifically, in solid oxide electrochemical cells (SOCs). This technique offers simple set-up, film quality control and mass production. In this study, LSM-YSZ, a promising component material for SOCs application was deposited on YSZ electrolyte via screen-printing. Specifically, the study aimed to investigate the effect of the solvent used in screen-printing on the quality of the deposited film. LSM-YSZ precursor powders synthesized via glycine-nitrate combustion process (GNP) were screen-printed on YSZ substrate using different solvents, ethanol and alpha-terpineol. The structure, morphology, and conductivity values of the GNP LSM-YSZ thin films using two solvents were compared. Results showed that both solvents produced a uniform distribution of rhombohedral LSM and cubic YSZ thin films with porous morphologies but alpha-terpineol solvent exhibited more agglomerated particles. Despite having this morphology, alpha-terpineol is still preferred than ethanol due to its reproducibility and scalability as it is less volatile than the other one. Moreover, there was no significant difference between the measured total conductivities of the half-cells using two solvents with the values of 4.63e-3 S/cm and 2.07e-3 S/cm at 700°C, and activation energies of 0.374 eV and 0.483 eV from 500°C - 700°C, for ethanol and alpha-terpineol, respectively.

(Digital Presentation) Facile Fabrication of Nickel and Sc-Doped Zirconia Cermet Electrode Thin Film on YSZ Substrate Via Screen-Printing for Solid Oxide Electrochemical Cells

Solid oxide electrochemical cells (SOCs) operating as either solid oxide fuel cells (SOFCs) or solid oxide electrolysis cells (SOECs) are widely known as promising advancements in green energy technologies for storage and high-efficiency energy generation. This study used a single screen-printing deposition method to fabricate a porous Nickel – scandia-stabilized zirconia (Ni-ScSZ) cermet electrode on a dense YSZ solid electrolyte substrate. The precursor powders were prepared via the glycine-nitrate combustion process. To investigate the effect of ink slurry solvent on the quality, structure, and morphology of the deposited films, ethanol, and alpha-terpineol were used. The screen-printed films were sintered at 1300°C for 6h and reduced under an Ar/5% H2 gas environment at 700°C for 2h to form porous electrodes. X-ray diffraction (XRD) analysis showed that all sintered NiO-ScSZ films exhibited cubic peak structures of both NiO and ScSZ. Scanning electron microscopy (SEM) micrographs and elemental mapping revealed finer morphology with good dispersion of NiO and ScSZ phases for sintered NiO-ScSZ films with alpha-terpineol as solvent. After exposure to Ar/5% H2 gas environment, a complete reduction of NiO to Ni was revealed by XRD for all Ni-ScSZ electrodes. Moreover, SEM micrographs of as-reduced samples showed an increase in porosity as oxygen was removed from NiO. Electrochemical impedance spectroscopy was used to determine the conductivity of the reduced Ni-ScSZ electrode films under Ar/5% H2 gas environment. The obtained total conductivity values upon reduction are 9.54x10-5 S/cm and 4.75x10-5 S/cm for ethanol and alpha-terpineol as solvents, respectively.

Facile Preparation of Porous Ni-YSZ Electrode Composite Material: From Highly Dense to Desirable Electrode Porosity Even without Pore Former

Ni-YSZ is a key electrode material for solid oxide electrochemical cells (SOC) applications, such as fuel or electrolysis cell applications. The number of active sites, specifically the triple-phase boundaries (TPB), strongly affects the electrode performance. Thus, in order to achieve good electrode performance, a desirable microstructure of the electrode is essential. This study investigated the effect of precursor particle size without using pore former in developing porous Ni-YSZ electrode materials. Precursors were prepared with different particle sizes using a planetary ball mill. In comparison, Ni-YSZ with carbon black as a pore former was also prepared. From the XRD patterns, major peaks can be attributed to the cubic phases of NiO and YSZ. SEM images revealed that a highly dense as-sintered NiO-YSZ electrode was achieved; however, a desirable porous microstructure was obtained after reduction to Ni-YSZ, even without a pore former. In comparison, the prepared electrode with carbon black pore former has a larger pore size than the sample prepared without pore former. The obtained total bulk conductivities for the reduced Ni-YSZ without pore former at 700 oC is 3.94x10-1 S/cm with Ea of 0.02 eV at 500-700 oC. Thus, a desirable porous Ni-YSZ electrode with more TPBs and high total conductivity can be achieved even without a pore former. Figure 1

Highly Conducting Sc and Y co-doped Zirconia Solid Electrolyte Thin Films Prepared via Pulsed Laser Deposition for Solid Oxide Electrochemical Cells Applications

Scandium (Sc) and yttrium (Y) co-doped ZrO2 thin films were fabricated via pulsed laser deposition (PLD). The target material, 4 mol% Sc2O3 and 4 mol% Y2O3 co-doped ZrO2 (ScYSZ), was first synthesized via a solid-state reaction. The ScYSZ thin film was deposited on SiO2-Si substrate by laser ablation, using a Q-switched Nd3+:YAG laser (λ = 266 nm) and substrate temperatures of 600 and 800 oC. Micro-structural and conductivity properties of the resulting as-deposited thin films were investigated. X-ray diffraction (XRD) sample patterns revealed that the as-deposited polycrystalline films can be indexed to a cubic structure. In addition, varying the oxygen partial pressures during the deposition was studied. FE-SEM images revealed dense and crack-free surface morphologies achieved at lower oxygen partial pressures (0.01 Pa and 0.1 Pa) and rough surface with porous morphology at high oxygen partial pressures (1.0 Pa and 10 Pa). The thickness of the film is about 120 nm for the thin film deposited at 800 oC substrate temperature (TS). The total conductivity of the thin film was measured using electrochemical impedance spectroscopy (EIS). Interestingly, the calculated total conductivity of the deposited ScYSZ thin film, 0.1 Pa and TS at 800 oC, revealed about 2.8x10-1 S/cmat 700 oC and with activation energy (Ea) of 0.78 eV from 500 oC to 700 oC. The fabricated as-deposited ScYSZ thin film is one of the highest reported highly conducting solid electrolytes that is a promising material for fuel cell or electrolysis cell applications.

Solid Oxide Electrochemical Cells for Nitrogen and Oxygen Production

Nitrogen and oxygen are both very important commodities with a wide variety of applications in industries, such as chemical, food and metallurgical plants as well as in the medical sector. Nowadays most of the nitrogen and oxygen are produced via air separation technologies such as cryogenic distillation (ASU) or pressure swing adsorption (PSA). Both ASU and PSA offer economical and mature ways for nitrogen and oxygen production at large (>100 ton/day) or medium scales (20-100 tons/day). If one can develop a technology for providing these gases in an energy efficient and cost effective way also at small scale, preferably driven by electricity only, this would enable new applications of the gases. Such a technology would match characteristics of the future green electricity system relying on small scale (few MWs) power generation and fluctuating production..In this work we present an efficient electrochemical process for N2 and O2 production based on a solid oxide electrochemical cell technology by oxygen extraction from air. Cells with a 53 × 53 mm2 size were produced by a conventional tape casting method. They consist of a ca.10 μm CGO (Ce0.9Gd0.1O2-δ) electrolyte sandwiched between composite electrodes made from either LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) - CGO, or LSF (La0.6Sr0.4FeO3-δ) - CGO. To boost performance at low temperature, the electrodes were infiltrated with Pr-oxide. The electrochemical performance with the different supports were characterized by obtaining current-voltage (iV) characteristics at different temperatures as well as through electrochemical impedance spectroscopy(EIS) with or without infiltration. For characterization, air was used as feed stock to the cathode compartment and air, or oxygen was used as sweep gas to the anode compartment. A voltage below 200 mV is needed to drive a current of 1 A/cm2 through the cell, which can provide a purity of 90% of N2 out at an operation temperature of 650 °C (see Figure 1a). The cells were demonstrated to operate for producing a 98% pure N2 stream without degradation over a 1500 h period (see Figure 1b).Further analysis show that the specific power consumption calculated based on the power input and outlet gas flow rate for 90% N2 production is ca. 0.1 kWh/m3 and the specific power consumption for 96% and 98% N2 production is 0.21 and 0.31 kWh/m3, respectively. A 3-fold increase in required power is observed when going from a N2 purity from 90% to 98%.Detailed electrochemical analysis and the electrochemical performance comparison between LSCF and LSF based mixed ionic electronic conductor (MIEC) electrodes will be presented. Factors limiting cell performance will as well as analysis of optimal point of operation in terms of energy consumption and reliability will also be discussed. Acknowledgment This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 862482. Figure 1

Novel Perovskite Structured Nd0.5Ba0.5Co1/3Ni1/3Mn1/3O3-δ as Highly Efficient Catalyst for Oxygen Electrode in Solid Oxide Electrochemical Cells.

Developing catalytic materials with highly efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for lower-temperature solid oxide fuel cell (SOFC) and electrolysis cell (SOEC) technologies. In this work, a novel triple perovskite material, Nd0.5Ba0.5Co1/3Ni1/3Mn1/3O3-δ, has been developed and employed as a catalyst for both ORR and OER in SOFC and SOEC operations at relatively lower temperatures, showing a low polarization resistance of 0.327 Ω cm2, high-power output of SOFC up to 773 mW cm-2 at 650 °C, and a high current density of 1.57 A cm-2 from SOEC operation at 1.5 V at 600 °C. The relaxation time distribution reveals that Nd0.5Ba0.5Co1/3Ni1/3Mn1/3O3-δ could maintain a slow polarization process at the relatively low operating temperature, offering a significant antipolarization advantage over other perovskite electrode materials. The Nd0.5Ba0.5Co1/3Ni1/3Mn1/3O3-δ electrode provides a low energy barrier of about 0.36 eV in oxygen ion mobility, which is beneficent for oxygen reduction/evolution reaction processes.

Enhanced high-temperature CO2 electrolysis on CeO2 by inducing under-coordinated dual-atom active sites

Stable CO2 electrolysis to CO and O2 in solid-oxide electrochemical cells (SOCs) is challenging due to the competitive carbon deposition. CeO2-based electrodes have shown advanced carbon-tolerant ability in SOCs. Here, by conducting density-functional theory calculations, we report highly selective CO2 to CO conversion catalyzed by a novel dual-atom site in CeO2 induced by substituting one Ce with two Pd (Ni or Cu). CO2 is effectively activated in the form of carbonate species (CO2*O) with oxygen strongly adsorbed by the under-coordinated dual-atom site, which then dissociates C–O bond with a 1.00 eV lower barrier compared to clean CeO2. By contrast, a 0.22 eV larger barrier is found for carbon deposition on dual-atom sites than on CeO2, leading to carbon suppression over dual-atom sites. Therefore, 2Pd (2Ni or 2Cu) dual-atom sites in CeO2 can significantly improve kinetics of CO2 reduction into CO because of the crucial role of their under-coordinated local structure in facilitating CO2 activation while preventing carbon deposition during CO2 electrolysis, which sheds light on rational design of dual-atom active sites in metal oxide catalysts.

Lowering the Temperature of Solid Oxide Electrochemical Cells Using Triple-Doped Bismuth Oxides.

Despite the great potential of solid oxide electrochemical cells (SOCs) as highly efficient energy conversion devices, the undesirable high operating temperature limits their wider applicability. Herein, a novel approach to developing high-performance low-temperature SOCs (LT-SOCs) is presented through the use of an Er, Y, and Zr triple-doped bismuth oxide (EYZB). This study demonstrates that EYZB exhibits > 147 times higher ionic conductivity of 0.44 S cm-1 at 600 °C compared to commercial Y-stabilized zirconia electrolyte with excellent stability over 1000h. By rationally incorporating EYZB in composite electrodes and bilayer electrolytes, the zirconia-based electrolyte LT-SOC achieves the unprecedentedly high performance of 3.45 and 2.02W cm-2 in the fuel cell mode and 2.08 and 0.95 A cm-2 in the electrolysis cell mode at 700 °C and 600 °C, respectively. Further, a distinctive microstructural feature of EYZB that largely extends triple phase boundary at the interface is revealed through digital twinning. This work provides insights for developing high-performance LT-SOCs.

Improvement of oxygen reduction activity and stability on a perovskite oxide surface by electrochemical potential

The instability of the surface chemistry in transition metal oxide perovskites is the main factor hindering the long-term durability of oxygen electrodes in solid oxide electrochemical cells. The instability of surface chemistry is mainly due to the segregation of A-site dopants from the lattice to the surface. Here we report that cathodic potential can remarkably improve the stability in oxygen reduction reaction and electrochemical activity, by decomposing the near-surface region of the perovskite phase in a porous electrode made of La1-xSrxCo1-xFexO3 mixed with Sm0.2Ce0.8O1.9. Our approach combines X-ray photoelectron spectroscopy and secondary ion mass spectrometry for surface and sub-surface analysis. Formation of Ruddlesden-Popper phase is accompanied by suppression of the A-site dopant segregation, and exsolution of catalytically active Co particles onto the surface. These findings reveal the chemical and structural elements that maintain an active surface for oxygen reduction, and the cathodic potential is one way to generate these desirable chemistries.

Innovative low-critical raw materials and medium-entropy perovskite for intermediate temperature solid oxide electrochemical cells

Ceramic proton conductive electrolytes are promising materials for reducing the operating temperatures of solid oxide cells. It is desirable to achieve such a target because, as a result, durability, cost of materials, electrochemical reactions and flexibility of its use can be significantly enhanced. A medium-entropy perovskite with the stoichiometric formula Ba0.5Sr0.5Zr0.5Zn0.5O3 was studied in the present work using limited amounts of critical raw materials. According to the performed analysis, it is possible to achieve complete phase purity at 1300 °C. Based on dilatometric measurements, the material can undergo significant densification starting at 1200 °C; at about 1550 °C the produced perovskite melts and degrades simultaneously. One of the most effective characteristics of the pure phase is its ability to absorb moisture and the excellent stability to redox mechanism. This material's characteristic was confirmed by a series of thermochemical procedures and XRD analyses. As a result of electrochemical measurements carried out on 93% dense pellet consolidated at 1350 °C, the material has a much better conductivity and activation energy than BZY.

(Digital Only Presentation) Effects of Ink Solvent on the Screen-Printing Fabrication and Morphology of LSM-YSZ Thin Films Deposited on YSZ Substrate for Solid Oxide Electrochemical Cells

Screen-printing is a cheap and easy thin film deposition technique utilized in energy devices fabrication, specifically, in solid oxide electrochemical cells (SOCs). In this study, LSM-YSZ, a promising component material for SOCs application was deposited on YSZ electrolyte via screen-printing. Specifically, the study aimed to investigate the effect of the solvent used in screen-printing and the effect of varying ink formulation on the quality of the deposited film. LSM-YSZ precursor powders synthesized via glycine-nitrate combustion process (GNP) were screen-printed on YSZ substrate using ethanol and alpha-terpineol solvents. The structure and morphology of LSM-YSZ thin films using two solvents were compared. Results showed that both solvents produced a rhombohedral LSM and cubic YSZ thin films and the use of a-terpineol solvent with higher solid content produced a desired uniform and porous morphology with homogenous pore distribution as revealed by XRD and SEM morphological results.

Highly Conducting Sc and Y co-doped Zirconia Solid Electrolyte Thin Films Prepared via Pulsed Laser Deposition for Solid Oxide Electrochemical Cells Applications

Scandia and yttria-stabilized zirconia (ScYSZ) have been widely used as electrolyte materials for solid oxide electrochemical cells (SOEC) applications due to its high ionic conductivity and stable mechanical and thermal properties. In this study, ScYSZ thin films were fabricated via pulsed laser deposition (PLD) method at substrate deposition temperature (Ts ) of 800 °C with varying oxygen oxygen partial pressures (). The as-deposited ScYSZ thin films were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and electrochemical impedance spectroscopy (EIS). XRD analysis revealed that all fabricated films, even with varying , have a polycrystalline cubic-fluorite structure. Morphological FESEM images revealed a good-quality dense ScYSZ electrolyte thin film with no visible cracks. Notably, a high total conductivity thin film of about 2.8x10-1 S/cm at 700 °C and low activation energy (Ea ) of 0.78 eV, from 500°Cto 700 °C, were achieved. Interestingly, the PLD-prepared ScYSZ dense solid electrolyte showed a higher total conductivity than the reported conductivities of zirconia-based solid oxide electrolytes.

(Digital Presentation) Facile Fabrication of Nickel and Sc-Doped Zirconia Cermet Electrode Thin Film on YSZ Substrate Via Screen-Printing for Solid Oxide Electrochemical Cells

Electrode materials play a key role in the performance of solid oxide electrochemical cells. In this study, screen-printing was used to fabricate a porous nickel – scandia-stabilized zirconia (Ni-ScSZ) cermet electrode on a dense YSZ solid electrolyte substrate. The effect of sintering temperatures, 1200°C and 1300°C, on the structure and morphology of the deposited films were investigated. The screen-printed films were sintered and then reduced under an Ar/5% H2 gas environment at 700°C for 2h to form porous electrodes. The sintered films exhibited NiO and ScSZ cubic phases from X-ray diffraction (XRD) analysis. A desired porous morphology of NiO-ScSZ film sintered at 1200°C was achieved compared to a denser morphology sintered at 1300°C as revealed by the scanning electron microscopy (SEM) micrographs. XRD patterns of reduced samples suggested a complete reduction of cubic NiO to Ni with an increase in porosity as observed from SEM micrographs.

Solid Oxide Electrochemical Cells for Nitrogen and Oxygen Production

This work presents an efficient electrochemical process for N2 and O2 production based on a solid oxide electrochemical cell technology by oxygen extraction from air. Cells with a 53×53 mm2 size consist of ca.10 μm CGO electrolyte sandwiched between composite electrodes made from either LSCF-CGO, or LSF-CGO were produced by a conventional tape casting method. To boost performance at low temperature, the electrodes were infiltrated with Pr-oxide. The electrochemical performance of the cells were characterized by iV and EIS at different temperatures with air used as feed stock to the cathode compartment and air, or oxygen used as sweep gas to the anode compartment. A voltage below 200mV is achieved to drive a current of 1A/cm2 through the cell, which can provide a purity of 90% of N2 at 650 °C. The cells were demonstrated to operate for producing a >98% pure N2 stream without degradation over a 1500h period at cell voltages below 255mV.

Challenges in practical button cell testing for hydrogen production from high temperature electrolysis of water

High temperature electrolysis of water using solid oxide electrochemical cells (SOEC) is a promising technology for hydrogen production with high energy efficiency and may promote decarbonization when coupled with renewable energy sources and excess heat from nuclear reactors. Over the past several decades there have been extensive scientific and engineering studies on cell materials and degradation behaviors that have greatly improved current density, decreased total resistance, and lowered degradation rates. Although the technology is now at a near-commercial level, maintaining consistency in cell testing and minimizing variance in practical testing environments is an often overlooked but crucial topic. To promote high quality data collection, testing procedures and balance of plant component details are extremely important to consider. This work discusses some key factors affecting the reproducibility of practical SOEC testing on the button cell level, namely, current collection layers, cell sealing procedures, the reliability of steam and hydrogen delivery systems, cell testing fixture design, and reduction procedures. To provide a baseline and a level of standardization for the SOEC community, this work also discloses details of the standard operating procedure and techniques adopted for o-SOEC testing at Idaho National Laboratory (INL).