bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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
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.

Figure 1
Ni/CGO-Based Electrolyte-Supported Cells During Co-Electrolysis: The Role of Feed Gas Impurities
Authors: Riegraf Matthias , Surrey Alexander , Costa Rémi 
Published: July 2021

The electrochemical generation of syngas via simultaneous co-electrolysis of steam and CO2 in high temperature solid oxide cells and its consecutive catalytic upgrade has attracted growing interest over recent years since this pathway offers a sustainable route to the production of synthetic fuels. However, most solid oxide cell technologies have been developed for durable and efficient fuel cell operation and thus, their use in electrolysis mode leads to the emergence of different lifetime-limiting degradation mechanisms. For instance, strongly cathodic polarization of the cermet fuel electrode leads to irreversible Ni migration away from the electrode/electrolyte interface. Furthermore, carbon deposition can become an issue when local non-equilibrium, carbon monoxide-rich gas phase compositions are formed. All of these mechanisms have been shown to be particularly harmful in Ni/YSZ-based fuel-electrode supported cells. Ni/Gadolinium-doped ceria (CGO) electrodes offer a potentially promising alternative to alleviate these issues due the intrinsic high electro-catalytic activity and carbon mitigating effect of the ceria phase. Furthermore, the higher operating temperatures commonly used for electrolyte-supported cell (ESC) architectures may mitigate carbon deposition and impurity adsorption due to thermodynamic considerations. In addition, the thinner electrodes employed in ESC could help to avoid the formation of CO-rich gas phases at the electrode/electrolyte interface due to enhanced porous diffusion and thus, further prevent coking. With regards to durability of the reactor, the purity of the feed gases steam and CO2 becomes of great importance.
In the present study durability aspects of industrial Ni/CGO-based ESC are investigated in co-electrolysis mode under various operating conditions by means of current-voltage characteristics and electrochemical impedance spectroscopy. Durability was evaluated at different current densities for times of >=1500 h. Post-mortem analysis was carried out with scanning electron microscopy (SEM) to correlate the observed degradation phenomena with microstructural changes, particularly Ni migration. It is shown that the steam inlet gas has to be carefully purified to avoid the deposition of silica in the fuel electrode. Furthermore, electrochemical measurements performed in dry CO2 electrolysis demonstrate that sulfur impurities in the CO2 feed gas must be removed to achieve low degradation rates.
Thin Film Barrier Layers with Increased Performance and Reduced Long-Term Degradation in SOFCs
Authors: Bernadet Lucile , Baiutti Federico , Martinelli Francesca , Torrell Marc , Morata Alex , Montinaro Dario , Tarancón Albert 
Published: July 2021

Gadolinium-doped ceria (CGO) is placed between yttrium-stabilized zirconia (YSZ) electrolyte and strontium-based electrode as a barrier layer to avoid the formation of SrZrO3 insulating phase during solid oxide fuel cell operation. This phase is observed in as-fabricated state-of-the-art cells, which evidences cation inter-diffusion during the sintering process [1]. The impact of this element to the degradation of cells is still under study, in part due to the high complexity of long-term tests necessary for the appropriate understanding of the involved phenomena. Among the efforts for improving barrier layers, the use of vacuum techniques such as sputtering and Large Area Pulsed Laser Deposition (LA-PLD) have been explored, allowing the implementation of dense layers at lower processing temperature compared with traditional deposition techniques (i. e. screen printing). CGO barrier layer thin film deposition and annealing parameters were previously optimized in a leading to an important increase of power density compared to a state-of-the-art button cell at 750ºC using a dense layer of 2 µm. Remarkable results were also obtained when the PLD barrier layer was up-scaled to large area cells of 80 cm2 and tested in short-stack configuration for long-term operation [2].
Here we present a thorough investigation of post mortem cells operated in short-stacks under realistic conditions during 15000h, comparing cells produced with state-of-the-art techniques with those produced by LA-PLD. At the light of the results, we provide tools for the improvement of the fabricated thin film layers, by finding the optimal combination between the protective role of the diffusion barrier layer, a good performance and the reduction of the PLD deposition time. Button cells with PLD barrier layer of 800 nm, 400 nm and 200 nm were fabricated and tested in SOFC mode at 750ºC. It is shown that the barrier layer thickness has no impact on the electrochemical performance and the durability which allows the use of thinner layers and a drastic reduction of the deposition time of the CGO barrier layer made by PLD.
Summed to the increased performance, the durability of the layers is evaluated, subjecting the cell with the thinnest film to an aging process for 3,500 h. Post-mortem characterization of the barrier layers and interfaces was conducted by Scanning-electronic microscope and Electron Probe Micro Analysis with Wavelength Dispersive X-Ray (EPMA-WDX) to observe any microstructural changes as well as any changes in composition due to cation inter-diffusion.
[1] Morales et al., Journal of Power Sources 344 (2017) 141-151.
[2] Morales et al. ACS Applied Energy Materials 1 (2018) 1955-1964.
Metal Supported Proton Conducting Ceramic Cell with Thin Film Electrolyte for Electrolysis Application
Authors: Zheng Haoyu , Han Feng , Sata Noriko , Riegraf Matthias , Dayaghi Amir Masoud , Norby Truls , Costa Rémi 
Published: July 2021

Solid oxide fuel cells and electrolysis cells (SOC) have been comprehensively developed as energy conversion and storage devices in recent years. Compared with oxygen ion conducting SOC, proton-conducting ceramic (PCC) cells are more suitable for the operation in the temperature range of 450~650 oC. The reduced operating temperature makes it especially attractive for steam electrolysis application aiming at valorizing waste heat from industrial processes. Moreover, during electrolysis in PCC cells, by design, the water-splitting reaction occurs at the oxygen electrode which enables the production of pure hydrogen at the fuel electrode.
Based on previous research on metal-supported solid oxide cells (MS-SOC)[1] at DLR, MS-PCC with thin film electrolyte were investigated in this present study. The low temperature fabrication route (< 1000 °C) was chosen to avoid the serious corrosion of metal substrate at high temperature (1300~1400 °C) which is necessary for making the dense BaZrO3 based electrolyte in traditional sintering routes. In this case, pulsed laser deposition has been used for preparing the 1~2 µm thick electrolyte. Porous ferritic stainless steel, which has been used as the substrate, was cut into a round shape of 18 mm in diameter. To mitigate the Cr diffusion from metal substrate and formation of impurity phase between the metal substrate and NiO/BaZrxCe0.9-xY0.1O3-δ (NiO-BZCY) anode functional layer during processing or operation, Sr-doped LaMnO3 (LSM) was employed as the barrier layer in between. Both LSM and NiO-BZCY layers were processed by lamination of tape-cast thin films onto the metal substrate respectively and successfully co-sintered below 1000 °C. The thermomechanical stability of the thin film electrolyte was investigated by simulating thermal cycles from room temperature up to 950 °C. Platinum and Ba1-xGd0.8La0.2+xCo2O6-
δ
[2] were considered as oxygen electrode materials. Electrochemical characterization was carried out in both fuel cell and electrolysis operations. Advantages and current limitations of the presented cell design are discussed.
Part of this work was supported by the project DAICHI funded by EIG CONCERT-Japan. The German part was funded by the Federal Ministry of Education and Research (project 01DR18002), the Norwegian part funded by the Research Council of Norway (project 284289). The China Scholarship Council is acknowledged for the doctoral scholarship of Haoyu Zheng (201806160173).
Figure.1 Scanning electron microscopy (SEM) image of the metal supported proton conducting cells.
[1] Costa R., Han F., Szabo P., et al. Fuel Cells, 2018, 18 (3): 251-259.
[2] Vøllestad E., Strandbakke R., Tarach M., et al. Nature Materials, Jul, 2019, 18 (7): 752-759.

Figure 1