bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication and Characterization of a Tubular Solid Oxide Fuel Cell with Impregnated Perovskite Electrodes
Authors: Nowicki Kamil Maciej , Wang Mei , Irvine John Thomas Sirr
Published: July 2021

Thanks to large efficiency and ability to work in both fuel cell and electrolysis mode Solid Oxide Cells (SOCs) could become a vital technology in the transition to the carbon-neutral energy sector based on hydrogen. However, large cost and low durability constrain their full-scale commercialization. These challenges are tackled in the present work. Tubular cells are produced by a simple and inexpensive method, suitable for mass production. The cells showed excellent activity, stability and redox resistance due to tubular design and fully ceramic electrodes. Thermal shock resistance testing showed that the cell is resistant to rapid temperature changes.

A thick supporting layer of the porous backbone was cast first, and a thin layer of electrolyte over it. After rolling into a tubular shape, the assembly was co-sintered and impregnated with functional perovskite materials. Co-casting allowed to achieve a strong interface and reduce the thickness of electrolyte. The impregnation gave the possibility to deposit a perovskite in temperature much lower than in state-of-art methods, preventing the undesirable reaction with zirconia electrolyte and reducing their densification, producing more active spatial microstructures with large surface area. Moreover, such electrodes are more thermally compatible with electrolyte as their bulk TEC is mainly controlled by the porous backbone made of the same material as the electrolyte.

Yttria-stabilized zirconia (Zr0.92Y0.16O2.08, 8YSZ) is used as the electrolyte, for the fuel electrode nickel doped lanthanum calcium titanate (La0.43Ca0.37Ni0.06Ti0.94O3-
γ, LCNT) was impregnated onto a porous 8YSZ backbone, while on the air electrode a lanthanum strontium ferrite (La0.8Sr0.2FeO3, LSF) was applied. These materials offer high activity and stability for a relatively low price. Electrochemical impedance spectroscopy (EIS), current-voltage (I-V) and potentiostatic measurements were carried out to characterize cell performance and cell’s stability during the test. The electrochemical testing showed improvement in the cell performances after electrochemical poling at high potential, due to facilitated LCNT reduction and exsolution of nickel nanoparticles.

The cheap fabrication method, competitive performance, attracting redox stability and thermal shock resistance, braking the major limitation for SOFC applicability, making it even suitable to be used in portable applications.
The “Innovation Liquid Energy” (ger. “Innovation Flüssige Energie” - IFE) Project: Development of a 1MW Power-to-Liquid Plant Based on Co-SOC Electrolysis and Fischer-Tropsch Synthesis
Authors: Hauth Martin , Reiter Bernd
Published: July 2021

The European climate protection program adopted in 2018 targets for a reduction in greenhouse gas emissions from the current 20% to 40% (compared to 1990) by 2030 ([1]), together with a simultaneous increase in the share of energy from renewable sources from the current 20% to 32%. In the transport sector, an increase in the share of renewable fuels from the current 10% to 14% is aimed for, with a maximum of 7% of this being Generation 1 fuels. Therefore, additional solutions such as power-to-liquid (PtL) fuels are needed to generate an immediate impact on existing fleets in order to achieve European and global CO2 emission targets in mobility.

The overall objective of the IFE (Innovation Liquid Energy) project is the development and realization of a Power-to-Liquid plant with a combined water and carbon dioxide high-temperature electrolysis (Co-SOEC) and a Fischer Tropsch synthesis for the production of synthetic fuel. By coupling these two processes in a way which enables heat integration, an increase of the overall electrical efficiency to 55% is to be achieved. The overall plant with a nominal electrolyser power of around 1 MW will constitute of several parts. Carbon dioxide is extracted from industrial waste gas or from a biogas/biomass plant and fed into the electrolyser process. There, a synthesis gas of hydrogen and carbon monoxide is produced based on an innovative Co-SOEC unit with an efficiency higher than 80%. In the next process stage, the syngas is fed into a low-temperature Fischer-Tropsch synthesis, where syncrude is produced with predominantly liquid and paraffinic products. The estimated output of Fischer-Tropsch products is around 500.000 L diesel-equivalent. The diesel fraction is targeted to meet the required quality of the EN15940 standard for alternative paraffinic diesel fuel.

The present work shows the status of the project and how specific challenges such as the reuse of the tail gas, the reuse of the aqueous product fraction and heat integration are addressed. Thereby a focus on the development of the co-SOEC unit and the optimization of the overall process towards highest efficiencies is being laid. Furthermore a techno-economic view on the potential cost of Fischer-Tropsch products is given, where, dependent on the electricity cost and full-load operating hours of the plant, FT-diesel costs in the range of 1-3 € seem reasonable (without tax and margin).

[1] The European parliament and the council of the European Union:DIRECTIVE (EU) 2018/2001, (L 328/82), Brüssel, 2018

https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018L2001&from=EN
Effect of Microstructure of the Anode Support Tubes Towards SOFC Performance
Authors: Sahu Sulata , Panthi Dhruba , Feng Hai , Du Yanhai
Published: July 2021

Reversible solid-oxide fuel cells (rSOFC) attract enormous attentions because of their capability to operate in both fuel cell and electrolysis modes. rSOFC with a tubular cell design has multiple advantages over a planar design for example allowing faster startup and shutdown. Successful fabrication of tubular cells needs to overcome numerous technological challenges, including control of its mechanical stress and high interlayer electrode resistance. The scope of the present work involves fabrication and testing of anode supported rSOFC single cells using both ionic conducting electrolyte and protonic conducting electrolyte. For the ionic conducting cells, the rSOFCs constituted Ni + yttria-stabilized zirconia (YSZ) anode support tube, Ni + scandia-stabilized zirconia (ScSZ) anode functional layer, scandia-stabilized zirconia (ScSZ) electrolyte, samarium doped ceria (SDC) protective layer, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) + SDC cathode functional layer, and LSCF cathode current collector layer, respectively. For the protonic conducting cells, BaZr0.1Ce0.7Y0.1Yb0.1O3-d (BZCYb) was used as electrolyte.

In this work, sequential dip-coating coupled with co-firing technique was implemented over the thin film cell structure fabrication. The nickel based tubular anode supports were made from various methods, including extrusion, freeze-casting and dipping processes. To achieve low interlayer resistance and dense electrolyte layer, we have optimized the ceramic slurry (ink) formulation parameters. Cell performance and microstructure of the rSOFC will be discussed and compared with the available data.
Production of Carbon Neutral Methanol Using Co-Electrolysis of CO2 and Steam in Solid Oxide Electrolysis Cell in Tandem with Direct Air Capture
Authors: Ferguson Katelyn M , Saafan Hussein , Wildeboer Emma K , Reeves Troy , Croiset Eric
Published: July 2021

The increasing concentration of carbon dioxide (CO2) in the atmosphere since the industrial revolution is a major contributor to climate change. Among the several options to tackle this issue, the removal of CO2 from the atmosphere and its subsequent use is becoming increasingly attractive. This paper presents a techno-economic feasibility study and quantification of the environmental benefits of combining direct air capture (i.e. capturing CO2 from the atmosphere) with co-electrolysis of water and the captured CO2 in a solid oxide electrolyser cell (SOEC). Using Aspen Plus, a direct air carbon capture process is modelled in tandem with SOEC to generate carbon monoxide and hydrogen, which are subsequently converted to fuels. The carbon capture model uses regenerative loops of sodium hydroxide and sodium carbonate as well as calcium hydroxide and calcium carbonate to selectively remove the dilute carbon dioxide from the air. Other than filtered air, the only other output of this process is a stream of gaseous water and carbon dioxide at an elevated temperature, which is fed to a SOEC stack. The SOEC model assumes that carbon dioxide is converted to carbon monoxide by the reverse water gas shift reaction and water is converted to hydrogen and oxygen through electrolysis. The different components of the SOEC and their inherent flows of materials and heat are simulated using unit operations available in Aspen Plus. The gas mixture from the SOEC (mixture of H2/CO/CO2/H2O) is further transformed into profitable fuels such as methane and methanol, whose respective processes are also simulated in Aspen Plus. Clean electricity sources are considered for the model and energy requirements are minimized through process synthesis; for example, there exists some good synergies between the direct air capture process and the SOEC to minimize the energy necessary to bring the SOEC feed to its operating temperature of ca. 800°C. Sensitivity analysis are performed on the entire process (direct air capture/SOEC/fuel synthesis) to reveal the effect of key operating parameters (e.g. conversion inside the SOEC, composition of SOEC inlet) on the production of fuels or amount of electricity requirement per amount of fuel produced.
Importance of Mixed-Conducting Materials for High-Temperature Fuel Cells Applications
Authors: Fung Kuan-Zong , Chang Ting-You , Tang Jhih Yu , Tsai Shu-Yi
Published: July 2021

In many electrochemical devices, mixed ionic/electronic conduction have received great attention. For instance, oxygen transport membrane (OTM) based on (Ba,Sr)(Co,Fe)O3 perovskite exhibit unique hole/oxygen ion mixed conduction behavior for oxygen separation application.

Accordingly, electrodes/electrolytes exhibiting both electronic and/or multiple ionic conducting properties have been used for high temperature fuel cell application. For example, mixed conducting electrodes based on composite electrode (e.g. LSM/SDC, LSM/YSZ) show improved SOFC performance in comparison to conventional electrode. Such unique conduction behavior may be rationalized based on defect chemistry consideration. Thus, the materials processing and microstructure design may become key issues to optimize their mixed conduction properties. For instance, better hole and oxygen conducing perovskite may be obtained when desired aliovalent dopant and oxidizing atmosphere are used.

Thus, the objective of this work is to conduct (1) fabrication/design of MIEC through defect-favored processing, (2) microstructure development for better gas transport, (3) characterization of conduction/interfacial kinetics for better electrodes/electrolytes performance. Desired analytical equipment such as SEM, XRD, electrochemical impedance spectroscopy (EIS) and cell testing are performed to conduct microstructural, structural and impedance analyses. The electrical conduction behavior of composite electrode/electrolytes will be discussed based on defect chemistry consideration and individual microstructure and morphology including pore size, pore distribution and interface area.
Inkjet 3D Printing of Functional Layers of Solid Oxide Fuel Cells (SOFCs) and Electrolyzers (SOEs)
Authors: Kawale Shrikant , Jang Inyoung , Alexander John , Kelsall Geoff
Published: July 2021

Hydrogen production using renewable energy sources could enable the technological objectives to be met of decarbonising electrical power generation, energy storage to mitigate renewable energy intermittency and balancing electrical power supply and demand. The required reactors and processes need to be efficient, economic, durable, and of scalable design and fabrication. Additive manufacturing, e.g. by inkjet printing of ceramic particles offers novel means of fabricating solid oxide fuel cells and electrolysers with reproducible geometries, predictable densities of triple phase boundaries, and upscaling of electrode | electrolyte interfacial areas using imaginative 3D structures, thereby decreasing specific costs.

We shall present results of using 3D inkjet printing, currently with ca. 10 mm lateral resolution, followed by sintering, for fabrication of SOFCs and SOEs. Having characterised their particle size distributions, zeta potentials and rheologies, colloidal dispersions of < ca. 200 nm yttria-stabilised zirconia (8-YSZ), NiO and lanthanum strontium manganite (LSM) particles were formulated. Having optimised inkjet printing parameters, these dispersions were used for printing 3D structures using a Ceradrop X-Serie piezoelectric DOD printer with a DIMATIX Sapphire QS-256/30 AAA printhead with 52 µm nozzle diameters. Gas-tight planar YSZ electrolyte layers were printed and sintered with ca. 10 mm thicknesses, onto porous Ni(O)-YSZ substrates. Porous LSM electrode layers also were printed on pressed YSZ substrates; cracking of printed layers due to capillary forces were mitigated by avoiding attractive depletion potentials and judicious control of sintering conditions. Detailed optimization of printing parameters, droplet size and substrate temperatures will be presented for electrolyte and electrode layers.
Development of Anode-Supported Solid Oxide Fuel Cell by Sequential Tape-Casting and Co-Sintering
Authors: Rodrigues Lays Nunes , Machado Marina , Moraes Leticia Poras Reis , Thyssen Vivian Vazquez , Fonseca Fabio Coral
Published: July 2021

Simple and cost-effective technologies to produce solid oxide fuel cells layers require control of thickness, homogeneity, and reproducibility. The manufacturing of a SOFC involves significant ceramic processing challenges to obtain layers with controlled microstructure. Currently, possibly the most common technique for large-scale production of SOFCs is the tape casting. In our study, a co-tape casting process was used to avoid delamination and ensure good adhesion between layers. The process consists of casting a thick anode tape of Ni/YSZ (60/40vol%) on top of a thin electrolyte tape of yttria-stabilized zirconia (YSZ). The slurries of both components were prepared using commercial ceramic powders, organic additives, and solvent. The starting materials were processed in a ball mill, to attain the appropriate homogeneity and viscosity for tape casting. A double doctor blade was used to control the thickness. Thermogravimetric and dilatometric analysis were performed to find the optimized heat treatment to remove the organics and densify the electrolyte while keeping a porous anode. The half-cells were then calcined and sintered at 1450°C/1h, with low heating and cooling rates to prevent cracks due to the different thermal expansion of the layers. The LSM cathode was then deposited by spin-coating and attached to the half-cell at 1100°C/1h. To verify the adhesion, thickness, and porosity of the layers, the sample was analyzed by scanning electron microscope. The electrochemical performance was evaluated by impedance spectroscopy and single cell tests under hydrogen and synthetic air. In this study we demonstrate a facile route to SOFC fabrication by co-casting and co-sintering, with relatively mild sintering conditions, with a good control of layer thickness, porosity and adhesion.

Figure 1
Catalytic Internal Reforming, Electrochemical Performance and Thermal Effect of Large-Scale SOFC Single Cell Using Oxygen-Bearing Low-Concentration Coal Mine Methane
Authors: Wang Xinxin , Ling Yihan , Tian Yunfeng
Published: July 2021

Coal mine methane is one kind of clean fuel with the global resource quantity of 260×1012 m3, however more than 230×108 m3 low concentration coal mine methane (LC-CMM) is directly emitted to the atmosphere annually in China, causing the severe energy loss and global warming effect. We proposed to utilize the LC-CMM through SOFC for realizing the efficient and clean conversion of LC-CMM. In this paper, the catalytic internal reforming efficiency, electrochemical performance and thermal effect of the large-scale 10cm × 10cm single cell were investigated using the oxygen-bearing LC-CMM as fuel. The results show that the peak power density and open circuit voltage can respectively reach 1.13 V and 100 mW cm-2 using the simulated LC-CMM (12.2 % CH4-4% O2) under 780 oC. Importantly, the stable discharging for nearly 400h using the oxygen-bearing LC-CMM were also be achived based on the large-scale single cell. The CH4 conversion and CO selectivity can also respectively reach 68.5% and 97.9%. The anodic temperature distribution of the large-scale single cell were tested, which implied that the exothermic oxidation reaction happen in the inlet side of anode, causing the higher tempeature of the area. However, the largest temperature gap in the whole large anode is smaller than 5oC, which cannot lead to the thermal distress. Therefore, above experimental results demonstrated the feasibility of efficient oxygen-bearing LC-CMM utilization through SOFC, which might create the opportunity to greatly improve the utilization ratio of LC-CMM and prevent the fuel waste and greenhouse effect by LC-CMM direct emission.
Improving the Stability of Series-Connected Solid Oxide Fuel Cells By Modifying YSZ Electrolyte Composition
Authors: Lim Hyung-Tae , Kim Youngje
Published: July 2021

YSZ based anode supported solid oxide fuel cells (SOFCs) were prepared, and two cells withdifferent electrolyte thicknesses were connected in series for the simulation of a cell-imbalanced fuel cell stack.Pure YSZ cells in a series connection exhibited a rapid degradation when a thick electrolyte cell was operatedunder a negative voltage. On the other hand, ceria added-YSZ cells in a series connection were stable undersimilar operating conditions, and the power density and impedance were about the same as those before tests.The improved stability was due to the reduction of internal partial pressure in the electrolyte by locallyincreasing the electronic conduction. Thus, we propose a new protection method, i.e., the local addition ofceria in the YSZ electrolyte, to extend the lifetime of a cell-imbalanced SOFC stack.
Investigation on B-Site Exsolved Titanates and its Structure-Property Relationship as Fuel Electrode in Solid Oxide Cells
Authors: He Shuai , Yue Xiangling
Published: July 2021

Exsolving B-site nanomaterials from A-site deficient perovskite lattice has been attracting great attention in recent years, for the development of highly efficient fuel electrode materials for solid oxide cells (SOCs). The emergent nanoparticles, such as Ni, Fe, Cu, Co or noble metals etc. are found exhibiting not only superior electrochemical catalytic activity towards fuel oxidation and reforming, but also excellent coking resistance and stability. Most recently, we discovered that electrochemical reduction can also trigger exsolution with higher efficiency and larger population than that through chemical reduction by H2. Nevertheless, the fundamental mechanism governing the exsolution with respect to the defect chemistry as well as the B-site doping level and composition is still not fully understood.

In this presentation, La0.43Ca0.37Ni0.06Ti0.94O3-δ (LCNT), La0.43Ca0.37Ni0.03Fe0.03Ti0.94O3-δ (LCNFT) and La0.8Ce0.1Ni0.4Ti0.6O3 (LCeNT) are selected as model electrode materials to exsolve Ni, Ni-Fe alloy and Ni-CeO2, respectively, under reducing atmosphere. The crystallography of each material is examined by X-ray Diffractometer (XRD), followed by Rietveld refinement to reveal the detailed crystalline information. It is found that the three materials are orthorhombic structure with oxygen octahedral out-of-phase tilting observed. The doping of Fe leads to the shrinkage of LCNT unit cell, and LCeNT is found to have the largest unit cell volume, probably due to the incorporation of cerium at A-site. In addition, the conductivity test indicates that LCNFT exhibits the highest conductivity after reduction (~13 S cm-1 at 900oC), while LCeNT shows two orders of magnitude lower conductivity at the same condition (~0.1 S cm-1). In order to understand how the material behaves under different conditions, the reduction and redox stability tests are also carried out to the mentioned materials, combined with thermogravimetric analysis (TGA) to monitor real-time weight loss or gain during reduction or oxidation. X-ray photoelectron spectroscopy (XPS) is performed as well to reveal the change in element valence state and ratio from the surface and bulk of the materials. Examined by secondary electron microscopy (SEM) and transmission electron microscopy (TEM), the evolution of the morphology and composition of the exsolved nanoparticles after the redox test is anticipated to give information on the stability of the material during long-term operation.

With attempt to uncover the relation between chemical and electrochemical reduction, the aim of this work is to reveal the intrinsic structure-property relationship of the titanate fuel electrode to fundamentally understand the exsolution behaviour and its impact on performance.
Determination of Partial Proton Conductivity in Fluorite-Type Oxides Using Electrochemical Technique
Authors: Yamaguchi Takuya , Ishiyama Tomohiro , Kishimoto Haruo , Bagarinao Katherine Develos , Yamaji Katsuhiko
Published: July 2021

Fluorite-type oxides such as YSZ and GDC are typical oxide ion conductors which are used for electrolyte materials for SOFCs. Although major charge carriers in these materials are of course oxide ions, it has been suggested that under wet conditions dissolved hydrogen becomes minor charge carriers. Existence of the dissolved hydrogen was confirmed by measuring deuterium concentration using SIMS, but whether the dissolved hydrogen really becomes charge carrier or not is still unclear. It is possible to examine this by whether proton conduction is detected or not in electrochemical measurements. In this study, in order to detect partial proton conduction in YSZ and GDC, oxide ion blocking measurements using hydrogen permeable Pd-plate as the blocking electrode were performed.

Pelletized 8YSZ and 10GDC powders by CIP at 390 MPa were sintered at 1300~1700 °C. The surfaces of the obtained dense pellets were mirror polished. As blocking electrodes, Pd-plates were fixed on upper surfaces of the pellets using Pd-pastes by firing them at 1000 °C and the boundaries between the pellets and Pd-plates were sealed using BaO-Al2O3-SiO2-glasses by firing them at 1250 °C. As reversible electrodes, Pd-pastes were painted on lower surfaces and fired at 1000 °C. Under the conditions with constant temperature and p
O2 (1×10−4 atm), constant voltage (20 mV) was applied between two electrodes with the reversible electrodes being positive electrical potential and the current responses to humidification of atmosphere by H2O and D2O were recorded.

In the case of 8YSZ sintered at 1300 °C, the current under dry atmosphere at 900 °C was 0.152 μA. When the atmosphere was humidified by 18°C H2O and D2O, the current increased to 0.226 and 0.206 μA, respectively. The current increment by humidification with H2O (ΔI
H2O = 0.074 μA) was approximately 1.4 times as compared to D2O (ΔI
D2O = 0.054 μA), which indicates that H+/D+ isotopic effect was reflected on the current increments. The current increments are suggested to be caused by conduction of dissolved hydrogen and deuterium because not oxygen but only hydrogen and electrons can pass through Pd-plates. This means that dissolved hydrogen becomes charge carriers, i.e., protons, in YSZ. Similar behavior was also observed for the case of 10GDC.
Conductivity Degradation of Transition Metal (Mn, Fe, Co) Doped Yttria Stabilized Zirconia by Phase Transformation
Authors: Zhang Wenrui , Ishiyama Tomohiro , Kishimoto Haruo , Yamaji Katsuhiko
Published: July 2021

Conductivity degradation behavior of 1 mol% transition metal (Mn, Fe, Co) doped yttria stabilized zirconia (YSZ) under SOFC operation atmospheres was examined by AC impedance technique under an OCV condition, using a test cell consisting of dry air, Pt / transition metal (Mn, Fe, Co) doped 8YSZ / Pt, 1.2 % H2O–H2, at 1173 K for 300 h. Phase transformation of YSZ from the cubic to the tetragonal phase was analyzed by Raman spectroscopy. The phase transformation occurs significantly in the area corresponding to the transition metal oxides reduction in the YSZ lattice. Cross section analysis of the tested electrolyte revealed that color changed into dark from the anode side surface to inside the electrolyte. Micro-Raman analysis indicated the phase transformation of transition metal (Mn, Fe, Co) doped 8YSZ from the cubic phase to the tetragonal phase. We have experimentally demonstrated that the conductivity degradation of transition metal (Mn, Fe, Co) doped YSZ is closely associated to the phase transformation under SOFC operation atmospheres at 1173 K. All the transition metal (Mn, Fe, Co) doped YSZ showed a lesser conductivity degradation and a lower phase transformation than the Ni doped YSZ. The Fe doped YSZ showed the least Conductivity degradation and lowest phase transformation during the transition metal (Mn, Fe, Co, Ni) doped YSZ under SOFC operation atmospheres at 1173K.
Experimental Investigation of Electrochemical Reactions Along SOFCs for Internal and External Reformed Methane
Authors: Höber Michael , Königshofer Benjamin , Pongratz Gernot , Boškoski Pavle , Nusev Gjorgji , Hochenauer Christoph , Subotic Vanja
Published: July 2021

A reliable and sustainable electrical and thermal energy supply is a basic requirement for modern societies and their food supply. Solid oxide fuel cells (SOFCs) provide a highly efficient solution to generate heat and electricity independent of weather conditions, which is essential for the operation of greenhouses. They can be used in combined heat and power plants or as stand-alone systems. Furthermore, they are able to utilize a wide variety of fuels such as biogas or gasified biomass. The possibility to operate as a stand-alone system and utilizing hydrocarbons makes them suitable for application in rural communities and agricultural industry. The main component of biogas, gasified biomass and reformed hydrocarbons is methane. Methane can be directly utilized in SOFCs, but however, it can cause undesired degradation of the fuel cells anode. To reduce the risk of performance deterioration, methane can be either (i) reformed externally thus generating syngas or (ii) mixed with a sufficient amount of steam under optimized operating temperature and load for the purpose of internal reforming. During the reforming process, several chemical reactions such as the steam reforming reaction and the water gas shift (WGS) reaction take place.

In this work, the off-gas compositions obtained at the reformer outlet after auto-thermal methane reforming when varying (i) steam to carbon ratio (H2O/C) and (ii) oxidizer used, e.g., air or pure oxygen, are used to fuel large planar electrolyte supported single cells with an active area of 81cm². Further tests are conducted by fuelling the SOFC single cell with methane and steam at different H2O/C. The holistic approach of this work combines thermal, electrical, electrochemical measurement methods and gas analysis to give insights in the methane utilization processes within SOFCs. Since different reactions take place as a function of the cell length and thus locally influence the cell temperature, the temperature distribution along the cell is monitored. In addition, the off-gas composition of the SOFC, the voltage and the current is continuously monitored. Furthermore, electrochemical impedance spectroscopy (EIS) measurements in combination with the distribution of relaxation time (DRT) analysis are performed at several current densities for each gas composition.

Figure 1
Electrical Properties of Novel La0.
2Sr0.7-xCaxTi0.95Fe0.05O3-δ Based Fuel Electrode for Solid Oxide Cell
Authors: Paydar Sara , Korjus Ove , Maide Martin , Kivi Indrek , Lust Enn , Nurk Gunnar
Published: July 2021

As the fuel electrode is a central component of solid oxide fuel cell (SOFCs), evaluation of novel fuel electrode materials for SOFCs has become a favorite research subject. Perovskite structure offers an excellent framework for altering the chemical and physical properties of a material due to its ability to accommodate many different cations. In the present research novel La0.2Sr0.7-xCaxTi0.3Fe0.7O3-δ (LSCFT) fuel electrode compositions have been synthesized by glycine-nitrate reaction for high-temperature solid oxide fuel cell application. For analysis of the influence of Sr/Ca ratio on the electrical conductivities of different compositions of LSCFT, the DC four-probe conductivity measurement method has been performed. Conductivities have been measured at three different atmospheres: synthetic air; 97% H2 + 3% H2O and in 1%H2 + 3% H2O + 96% Ar. The crystal structure and microstructure have been studied using X-ray diffraction and SEM, respectively to confirm the purity of phase and percentage of porosity.

In previous studies by Irvine et al. [1] has been demonstrated the effect of calcium doping on A-site deficient lanthanum strontium titanate, which displayed enhancement of its electrical conductivity and maximum conductivity was observed for La0.20Sr0.25Ca0.45TiO3 (LSCT) composition. Moreover, the same composition was tested and it confirmed as an active fuel electrode in fuel cell conditions, where good performance was achieved [2].

Keywords: Fuel electrode, Electrical conductivity, Layered Perovskite, MIEC material, high temperature SOFC.

[1] Aljaberi AD, Irvine JTS. Ca-substituted, A-site deficient perovskite La0.2Sr0.7TiO3 as a potential anode material for SOFCs. J Mater Chem A 1 (2013) 5868-74.

[2] Verbraeken MC, Iwanschitz B, Mai A, Irvine JTS. Evaluation of Ca doped La0.2Sr0.7TiO3 as an alternative material for use in SOFC anodes. J Electrochem Soc 159 (2012) F757-62.
Evaluation of Transport Properties of Lanthanum-Based Proton-Conducting Composite Electrolytes
Authors: Tajima Seiya , Matsuo Hiroki , Otomo Junichiro
Published: July 2021

For efficient energy conversion and energy storage, developing highly efficient hydrogen permeable membranes is a crucial issue. Ceramic hydrogen permeable membranes, i.e., protonic electronic mixed conductors, work on bipolar transport of protons and electrons. Ceramic composite membranes meet this requirement with chemical and thermal stability, and they can be used not only as hydrogen permeable membranes but also as electrolytes in protonic ceramic fuel cells (PCFCs). Although improvement in protonic conductivity at heterointerfaces between constituting materials and/or space-charge relaxation around the resistive grain boundaries can be possible origins of the enhanced hydrogen permeability in the composite electrolyte membranes, its detailed mechanisms have not been clarified yet and the strategy of material design for composite membranes has not been established. In this study, the transport properties of composite electrolyte membranes consisting of protonic conductors and electronic conductors are investigated to realize highly efficient PCFC operating at low temperatures and to clarify the principles of carrier transport in the composite membranes. For the protonic conductor and the electronic conductor, we selected La2Ce2O7 (LDC) with a fluorite structure and La0.3Sr0.6TiO3 (LST) with a perovskite structure, respectively. The composite membrane composed of LDC and LST (LDC/LST) with various LDC to LST ratios was prepared by a solid-state reaction. Phase stability of LDC and LST were investigated by X-ray diffraction (XRD) measurements. Transport properties of hydrogen permeation cells using the LDC-LST composite membranes with Pt electrodes were assessed by electrochemical impedance spectroscopy (EIS) measurements and hydrogen permeation measurements. Hydrogen fluxes were measured by gas chromatography. The EIS measurements revealed that the grain-boundary resistance was reduced for the LDC/LST composite membrane in comparison with an LDC membrane. In particular, LDC/LST (weight ratio 1:2) showed the smallest grain-boundary resistance of 26 Ω cm at 600°C under 1%H2/Ar among the measured samples. Besides, the hydrogen permeation measurement showed that LDC/LST exhibited higher hydrogen permeability than the LDC membrane. In addition, the hydrogen flux of LDC/LST (1:2) was almost twice as high as that of LDC at 600°C. The low grain-boundary resistance and the high hydrogen permeability of LDC/LST composite membrane suggests that the introduction of LST accelerates the proton conduction in the membrane.
Synthesis and Characterisation of P-Doped Sr2MnFeO6-δ Systems
Authors: James Matthew Samuel , Berry Frank J , Marco Jose F , Slater Peter R.
Published: July 2021

Perovskite type and related materials have attracted considerable interest as both electrolyte and electrodes within Solid Oxide Fuel Cells. Traditionally, doping with aliovalent cations of similar size on either site has been used to alter materials properties to enhance performance of the materials in these cells. However, recent literature has shown that anion incorporation strategies have also been successful in optimising electrical and ionic properties of perovskites and related structures. The two most successful anion doping strategies, are fluorine doping and oxyanion doping, the latter which is the focus of our work.

In particular, our recent work has focused on doping with various oxyanions (Carbonate. Borate, Phosphate, Silicate, Sulphate) in perovskite and related structures. [1-3] In previous work, we showed how small amounts of silicate doping can cause structural changes that lead to large increases in conductivity such as in the case of (Ca/Sr)2MnFeO6-
δ.[4] In view of this, we have extended these studies to examine the structural modifications caused by PO4
3- doping and the consequent effect on electrical conductivity.

[1] C A Hancock, J M Porras-Vazquez, P J Keenan, P R Slater, Dalton Trans, 2015, 44, 10559-10569

[2] J Deakin, P Slater, J. Solid State Chem 2021, 294, 121870

[3] A. Jarvis, P R Slater Crystals 2017, 7(6), 169

[4] A D Smith, M S James, P R Slater, ECS Trans. 2019 91(1) 1425-1436
Jet Fuel Desulfurization for Portable Solid Oxide Fuel Cell Applications
Authors: Du Yanhai , Panthi Dhruba , Feng Hai
Published: July 2021

Solid oxide fuel cells (SOFCs) are capable of utilizing energy-dense hydrocarbon fuels such as jet fuels for highly efficient power generation. Currently, a major challenge for using the jet fuel (e.g. JP8) in SOFC power systems is its sulfur content, which poisons the SOFC catalyst and anode. Sulfur contents in jet fuels could be as high as 3000 ppm although typical sulfur contents could be in the range from 550 and 750 ppm. The reduction of sulfur to <1 ppm is generally desired and required to ensure reliable SOFC operation. Various technologies have been developed to remove sulfur from jet fuel. However, most of these technologies are designed for large-scale desulfurization at industrial facilities or for stationary applications. Due to their complexity and substantial weight and size, these systems are not suitable for onboard integration with portable fuel cells. Therefore, our research aimed at developing a lightweight, compact desulfurization reactor for onboard applications. After several versions of improvements, including the use of selective laser sintering (SLS) 3D printing method, we have developed a miniature one-piece stainless-steel reactor which is capable of removing >99.5% sulfur in the jet fuel with the final sulfur concentrations close to a sub-ppm level. The reactor could be adapted to the desulfurization of other liquid hydrocarbon fuels such as gasoline and diesel. The reactor designs, desulfurizing materials, operation conditions and effectiveness of the technology will be discussed in this paper.
Development of a High-Efficiency, Low-Cost Hybrid SOFC/Internal Combustion Engine Power Generator
Authors: Braun Rob , Floerchinger Gus , Wahlstrom David , Sullivan Neal P. , Vincent Tyrone , Danforth Robert , Bandhauer Todd , Olsen Daniel , Windom Brett
Published: July 2021

The unique and beneficial characteristics of solid oxide fuel cell (SOFC) technology hold much promise for their eventual widespread adoption in numerous residential and commercial building applications. Nevertheless, cost and durability challenges remain that currently limit SOFC technology penetration in stationary energy applications. Under the U.S. DOE ARPA-E INTEGRATE program, the Colorado School of Mines and it partners are developing a novel hybrid stationary power system comprised of an intermediate temperature (600°C), metal-supported solid oxide fuel cell stack (from Ceres Power) integrated with a high efficiency stationary engine and novel balance-of-plant (BOP) equipment. In collaboration with Colorado State University, Kohler Power Systems, and Air-Squared, Inc., the project aims to demonstrate a system that can generate power (125 kW) from natural gas at high electric efficiency (>70%-LHV), and low cost (<900 $/kW). Project development activities on the hybrid SOFC/IC engine system development and requirements are presented and discussed, including experimental results from critical balance-of-plant equipment and techno-economic outlook.

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Local Characterization of a Solid Oxide Cell Operated in Fuel Cell and Electrolysis Mode Using Lock-in Thermography
Authors: Jeanmonod Guillaume , Van herle Jan
Published: July 2021

Operando characterization of SOCs generally relies on current–voltage measurements that provide the spatially averaged electrochemical response of the SOC. However, these methods do not fully capture the spatial distribution of the operating conditions (e.g., gas composition, current density). Local information on the operating conditions can be gained by using operando optical characterization methods. In this work, the spatial distribution of the electro-thermal response of an SOC with a 15 cm2 active area operated in fuel cell and electrolysis mode was investigated using lock-in thermography. Lock-in thermography consists of stimulating the solid oxide cell with a sinusoidal current perturbation and analyzing the local thermal response using Fourier transforms. A camera with a silicon-based sensor was used to record the transient temperature field on the oxygen electrode (i.e., the cathode in fuel cell operation) via a specifically designed optical access. The field of view of each pixel was approximately 0.03 mm x 0.03 mm. The Fourier transform generates a compact data set that can be conveniently represented by a phase and amplitude or a real and imaginary image. Using a real–imaginary representation provided a better thermal response contrast than an amplitude–phase representation. The local thermal response was found to be dependent on the direct current bias and the frequency of the current perturbation. The thermal response of the SOC was laterally and longitudinally inhomogeneous, thereby demonstrating the capability of active thermography to characterize the local behavior of an SOC in operando. Lock-in thermography is thus a promising method for defining regions of interest for post-mortem analysis using electron microscopy and helping to link highly localized post-test analysis with spatially averaged operando characterization methods.
Nanoscale Analysis of LSM/YSZ Interfaces within Composite Cathodes for Commercial Solid Oxide Fuel Cells
Authors: Picard Yoosuf N. , Poplawsky Jonathan D. , Lee Shiwoo , Abernathy Harry W.
Published: July 2021

While performance degradation for solid oxide fuel cells (SOFCs) comes in many forms, one important contributor is cation transport during long-term operation. This transport alters the chemical composition at electrode/electrolyte interfaces. These interfaces are carefully engineered to provide the critical reaction sites for oxidation and reduction reactions that regulate SOFC electrical production. Therefore, fundamental understanding of the chemical evolution of these interfaces is critical. The current study coordinates scanning transmission electron microscopy (STEM) with atom probe tomography (APT) in order to probe composition at the nanoscale across cathode/electrolyte interfaces for anode-supported commercial SOFCs. These SOFCs contain a porous composite cathode layer, consisting of sintered (La0.8Sr0.2)0.95MnO3 cathode particles and yttria-stabilized zirconia (YSZ) electrolyte particles. SOFCs are operated up to 500 hours in duration at a current density of 0.75 A/cm2 (or at open circuit) and at an operation temperature of 800°C. Measured cell voltage increases over the first 100 hours of operation, followed by a steady and linear drop in cell voltage that translates to 5.35% performance loss per 1000 hours. STEM-based energy dispersive spectroscopy (EDS) indicates nanoscale Mn-oxide formation at LSM particle surfaces after 500 hours of operation. Compositional profiles acquired by APT across LSM/YSZ particle interfaces indicate as-sintered interfaces are chemically well-defined, but La and Mn penetrate up to 5 nm into YSZ particles over the course of 500 hours. Additionally, as-sintered LSM particles exhibit measurable Mn enrichment within 20 nm of an adjacent YSZ particle. After 100 hours of operation, A-site deficiency is restored for LSM particle surfaces adjacent to YSZ. Meanwhile, the YSZ composition adjacent to LSM exhibits depletion in Y content over the first 100 hours of operation. These results suggest that initial cell voltage increase within 100 hours of operation corresponds to both Mn and Y transport at LSM/YSZ interfaces. STEM-based electron energy loss spectroscopy (EELS) provides additional insight regarding local cation valence states in relation to measured composition variations for these LSM/YSZ interfaces.
Different Approaches to Predict and Optimize an SOC Performance: Experimental and Numerical Study
Authors: Subotic Vanja , Eibl Michael , Thaller Thomas , Harter Philipp , Hochenauer Christoph
Published: July 2021

Solid oxide cells (SOC) provide a great potential to enable desired transition to an efficient, environmentally friendly and low-carbon energy system. Their great advantage is the capability of a reversible operation, which enables to utilize fuels to generate electricity and heat, or in a reversible mode to utilize electricity, steam and carbon dioxide to generate valuable fuels. Nevertheless, in order to accelerate their commercialization, the main criteria such as reliability, stability and degradation prevention at its preliminary stage have to be ensured. In order to fulfil these requirements, different optimization steps are necessary, starting with the material development, over cell, stack and system manufacturing, towards optimized operating environment. In this study we applied different approaches to (i) predict and optimize the cell performance, (ii) predict different failure modes, and thus to (iii) prolong the SOC lifetime.

A design of experiment was made in order to cover a range of different parameters and to use them for the further model validation. The experimental investigations have been performed employing both conventional and non-conventional methodologies, e.g. total harmonic distortion (THD) analysis. For the purpose of experimental investigations, the cell was fuelled with humidified hydrogen or humidified methane, whereby to generate hydrogen purely steam electrolysis was employed. Different parameters such as operating temperature, fuel volume flow, etc. were varied and their impact on the cell performance was studied. On the other hand, two different modelling approaches were considered in order to predict and optimize the cell performance. The first one is based on a physical model, which enables very precise performance prediction, and suggests the required optimization steps. The second one is based on the artificial intelligence, which enables to determine best appropriate operating conditions using the information from previous experiments carried out.

As an illustrative example, Fig. 1 compares different approaches, such as the temperature monitoring over the entire cell surface and the electrochemical impedance spectra both simulated and subsequently validated using the experimental data. Within this study we show that the cell performance can be optimized employing different simulation aspects with the aim of time-saving calculations. Moreover, when employing non-conventional online monitoring tools, an early degradation prediction is possible thus significantly prolonging the cell overall lifetime.

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Enhanced Long-Term Durability of Solid Oxide Electrolysis Cells by Microstructure Tailoring of the Air Electrode
Authors: Mehran Muhammad Taqi , Lim Tak-Hyoung
Published: July 2021

High-temperature solid oxide electrolysis cells (SOECs) provide greater efficiency and may potentially provide future technology to meet the enormous energy storage needs generated by the surge in the availability of intermittent solar and wind electricity. However, in implementing this SOEC technology, the high polarization losses and long-term degradation of the SOEC electrodes are the bottlenecks. In this research, we tailored the microstructure of SOEC air electrode to improve electrochemical efficiency and increase the stability of the air electrode. The optimization of the microstructure culminated in a 30% improvement in SOEC electrochemical performance at 800 °C for H2O conversion and considerably improved long-term stability for >1000 hours. The Post-test SEM and TEM investigations suggested that delamination of the air electrode was prevented due to effective microstructure tailoring, and resistive interfaces forming Sr diffusion were suppressed inside the barrier layer and electrolyte. Due to the increased triple phase boundary density, porosity at the interface, and greater active surface area of the electrode, the buildup of the oxygen partial pressure over the electrolyte/barrier layer/air-electrode was decreased.