bluuebunny/crossref_metadata_2025_split huggingface dataset:
Screen Printed Porous La0.20Sr0.25Ca0.45TiO3 Fuel Electrode Scaffold Microstructures: Optimisation of Interaction with Impregnated Catalysts for More Durable Performance
Authors: Price Robert , Cassidy Mark , Schuler J. Andreas , Mai Andreas , Irvine John T. S. 
Published: February 2020

Solid Oxide Fuel Cells (SOFC) offer an efficient method of electricity and heat production through electrochemical conversion of hydrocarbon fuels (e.g. methane) rather than direct combustion in conventional boiler units. The current industrial standard SOFC anode material is the Ni-based cermet. Although it shows high electrocatalytic activity for H2 and CO oxidation, it suffers from redox instability, Ni-grain agglomeration, gas feed sulfur intolerance and severe coking in the presence of hydrocarbon fuels. This deactivates the catalyst over time, hence a suitable replacement anode material is highly desired. La0.20Sr0.25Ca0.45TiO3 (LSCTA-) is a promising candidate for this role, acting as a ‘backbone’ structure into which electrocatalytic particles (NiO and CeO2) may be impregnated. This material has previously been used as an anode material in short-stack and full-scale testing at Hexis AG. Short-stack (5 cells) tests showed initial good performance (running at 200 mA cm-2) at 900 °C, however degradation was observed between 50 – 100 hours of operation. 1 Whilst in 1kW (nominal) Hexis Galileo 1000 N micro combined heat and power unit tests, an initial power output of ~700 W was obtained, decreasing to 250 W after 600 hours. 1 Post-test analysis revealed that non-optimal anode backbone microstructures and a small layer thickness led to poor current distribution and the generation of localised temperature ‘hotspots’ within the cells, leading to degradation of stack performance over time 1 (despite the initial comparability to the Ni-CGO standard at Hexis). Current research is focussing on the optimisation of the interaction between the backbone microstructure and impregnated electrocatalytic particles in order to improve electrochemical performance whilst minimising degradation. This paper will discuss initial research into optimisation of screen printed anode structures and the interaction with impregnated particles, including: NiO, CuO, CeO2 and lanthanum strontium chromium manganite (LSCrM).
Reference:
1. Verbraeken, M. C. et al. Short stack and full system test using a ceramic A-site deficient strontium titanate anode in 11th European SOFC and SOE Forum, 1–13, (2014).
Microstructure-Based Damage Modelling of Plasma Sprayed Ceramic Coatings in SOFC-Layer Systems
Authors: Guski Vinzenz , Krebs Axel , Weber Ulrich , Schmauder Siegfried 
Published: February 2020

Solid oxide fuel cells (SOFC) have developed to promising energy conversion devices for many applications. However, operation conditions under elevated temperatures, especially high temperature regimes and repeated temperature changes imply extreme demands for the used materials, questioning durability and reliability of such devices.
The scrutinized SOFC isolation layer system as shown in Figure 1 consists of a staple of ceramic layers sprayed on a steel substrate (interconnector). The main focus in this project is investigating application induced failure mechanisms under service conditions.
A newly developed ceramic of Mg-spinel type offers self-healing capabilities (Fig. 2). The self-healing effects provide fracture annihilating potential and promising mechanical capabilities. The manufacturing process of these ceramics causes a complex microstructure with structural defects such as pores or debonded splats. Splats are rapidly solidified molten ceramic particles on a substrate. Residual stresses, caused by quenching stresses during manufacturing as well as thermo-mechanical mismatch stresses due to temperature change may lead to crack initiation in the ceramic and subsequent mechanical weakening effects, respectively.
We present a microstructure-based approach to simulate the influence of thermal cycling on the ceramic coating stress evolution. This stress evolution and, thus, the damage behaviour is affected by the above mentioned influences. The numerical model represents a SOFC system which consists of a ceramic layer on a steel substrate and a thermally grown oxide (TGO) interlayer (Fig. 3). Assuming fracture mode I, the load case normal to the crack plane, the focus is set on the evolution of principal stresses in the ceramic microstructure.
The results of micromechanical simulations show how stress localisations due to structural defects such as pores or microcracks heavily influence this stress evolution and, therefore, the crack initiation in the ceramic layer.
We found the directions of the principle stresses in the microstructure facilitate delamination of the layer. Parameter studies show how residual stresses, TGO and interface roughness affect the stress evolution in the ceramic layer. A comparison of the new self-healing ceramic with a standard reference material point out the promising properties of this newly developed material. Detailed microstructure analyses and insights provide an understanding of the main failure mechanisms of the ceramic layer in depth and deliver clear optimization potentials for sprayed ceramic layer systems of SOFCs.

Figure 1
Three-Dimensional Computational Fluid Dynamics Modelling for a Planar Solid Oxide Fuel Cell of a New Design
Authors: Pianko-Oprych Paulina , Zinko Tomasz , Jaworski Zdzislaw 
Published: February 2020

The aim of the work is to investigate the electrochemical processes of a planar Solid Oxide Fuel Cell (SOFC) and to estimate the performance of a novel SOFC design. The design involves cross-flow bipolar plates. Flow channels were designed to connect pairs of four orifices at the corners of the SOFC plates. Each of the bipolar plates has an air channel system on one side and a fuel channel system on the other side. One pair of channels in adjacent plates is used for the air flow along the cathode electrode, the other for the fuel flow along the anode of each cell. A schematic of the design proposed by Bossel [1] is shown in Fig. 1.
Figure 1. A schematic of the proposed planar SOFC design:
(a) cathode side view, (b) anode side view [1]
A three-dimensional Computational Fluid Dynamics (CFD) model for an anode-supported planar SOFC with complex bipolar plates has been developed using the ANSYS Fluent code with additional Fuel Cell Tools module. The conservation equations of mass, momentum, energy and species as well as electrochemical models were solved for the fuel cell. The distributions of temperature and gas flow through the gas channels and PEN (positive electrode/electrolyte/negative electrode) structure were studied. The results identified the most susceptible areas for significant increase of the temperature at high current density, which can lead to hot spots formation and destruction of the electrodes. Knowledge of such parameters as the flow fields, pressure losses or temperature variation over the fuel cell area allowed to validate the effectiveness of the new SOFC design and is useful in further design modification.

Acknowledgments

The research programme leading to these results received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement no [325323]. Acknowledgments are due to the partners of SAFARI project. The work was also financed from the Polish research funds awarded for the project No. 3043/7.PR/2014/2 of international cooperation within SAFARI in years 2014-2016.
[1] U. Bossel, Rapid startup SOFC modules, Energy Procedia, 28, 2012, 48-56. DOI: 10.1016/j.egypro.2012.08.039.

Figure 1
A High Resolution Multi-Physics Numerical Model for Planar SOFC Stack
Authors: Li Ang , Fang Xiurong , Lin Zijing 
Published: February 2020

An SOFC stack is the basic functioning unit of SOFC as an electrical power generation device. The physical condition of an operating SOFC stack is vastly different from that of a laboratory button cell. The ability to analyze the performance characteristics of SOFC stacks is immensely helpful for advancing the SOFC technology for large scale commercial applications. Here we report a successful development of a high space resolution multi-physics mathematical model for full scale planar SOFC stacks which is, to the best of our knowledge, the first of its kind.
This 3D stack model takes into account the coupled physical processes of mass, charge and heat transport, chemical and electrochemical reactions, applicable for both methane and hydrogen based fuels. The computational domain contains all components of the stack, including fuel and air channels, internal manifolds, cathode-electrolyte-anode assemblies, interconnects, seals and frames. The computational model is constructed using the commercial CFD software, FLUENT®, supplemented with in-house developed external subroutines to ensure all governing equations and physical properties are correctly coupled and solved successfully. Boundary conditions for the stack and that between material components are all properly incorporated into the computational model.
To illustrate, Figure 1 shows a geometric model for a 30-cell stack with a counter- or co-flow design. The size of the stack is 136mm 143mm 133mm. The manifold consists of two/three gas inlet-outlet channels for each air or fuel flow. Every fuel cell consists of 30 channel-rib pitches, i.e., there are 900 repeating units for the electrochemically active area of the 30-cell stack. To properly resolve all the stack components involved, the computational model consists of a total of about 27 million grids.
Multi-physics numerical simulations of this truly high resolution computational model of 30-cell stack have been successfully performed in a 2-CPU/16-core PC. Detailed information about the distributions of physical quantities is revealed, e.g., concentrations of chemical species, temperature profile, current density and electrical potential distributions, chemical and electrochemical reaction rates, etc.
To summarize, the goal of performing detailed multi-physics simulations for realistic planar SOFC stacks has been achieved. Performance simulation with this high resolution, high computing efficiency numerical model can do much to advance the SOFC technology by improving the stack design and optimizing the operating parameters.

Figure 1
High Efficient Combined Heat and Power SOFC System for Residential Power Applications: Lifetime-Efficiency-Simulations Using AspenPlusTM
Authors: Spieker Carsten , Spitta Christian , Noponen Matti , Hallanoro Paul , Ruetten Thomas 
Published: February 2020

High temperature Solid Oxide Fuel Cells (SOFC) systems are high efficient energy conversion systems with low emissions e.g. for residential power applications. The objective of this work is to provide a flexible model of a SOFC system that is capable of predicting system performance in a wide range of operating conditions as well as predicting system lifetime performance based on experimentally determined SOFC performance and endurance curves. The system model is developed using AspenPlusTM unit operation blocks and the SOFC electrochemical model is implemented using the embedded AspenPlusTM Microsoft Excel Workbook. Validation of the model is performed by comparison to experimental results.
The adaption of this model to different SOFC system simulation approaches will be discussed. Furthermore for a SOFC based mCHP system development simulation results predicting an electrical efficiency higher than 50 % and an overall system efficiency higher than 85 % for the whole lifetime will be presented.
Effects of Lamination Conditions on the Performance of Anode-Supported Solid Oxide Fuel Cells
Authors: Timurkutluk Bora , Timurkutluk Cigdem , Ciflik Yelda , Korkmaz Hatice , Kaplan Yuksel 
Published: February 2020

Solid oxide fuel cells (SOFCs) operate at high temperatures and produces electricity and heat energy from fuels in an electrochemical way. Membrane electrode assembly (MEA) composed of a dense electrolyte coated with two porous electrodes on each side is generally constructed on the electrolyte. However, high operation temperatures are required to obtain acceptable performance values due to high electrolyte resistance as a result of the use of thick electrolyte layer as a mechanical support for MEA. Alternatively, the cells can be fabricated as anode-supported where the anode is responsible for supporting the cell mechanically. By doing so, the operation temperature can be lowered due to reduced electrolyte thickness. In this study, the effects of isostatic pressing parameters i.e. temperature and pressure for NiO/YSZ anode support on the anode-supported cell performance and the microstructure of the anode support are investigated. The experimental results reveal that the cell performance is strongly influenced by the pressing parameters. In this aspect, the optimum pressing temperature and pressure are found to be 50 °C and 40MPa, respectively.
Effect of Cathode Contacting on Anode Supported Cell Performances and Degradation
Authors: Spotorno Roberto , Piccardo Paolo , Schiller Guenter 
Published: February 2020

Stacking Solid Oxide Fuel Cells implies the use of contacting layers, especially in the cathode compartments where ohmic losses are introduced at the interface between the electrode and the interconnect due to the high interfacial resistance and the lowered contact area caused by geometrical and porosity issues. Such losses compromise the current distribution over the electrodes strongly influencing the system performances in terms of power outputs. The contacting issues are weakly dependent on the operating conditions compared to other dissipative contributions related to the cells. This implies the need to solve them at the structural level in order to ensure high system performances. A dedicated testing setup has been used to test anode-supported cells with different contacting solutions. The contact geometry effect has been evaluated comparing the use of platinum meshes and stamped metallic bipolar plates (Crofer 22 APU) as current collectors. Additionally, the application of a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) paste between the cathode and the interconnect allowed to estimate the beneficial effect of the contacting layer enhancing the current distribution at the cathode side of the cell. The system performances have been investigated by means of current-voltage curves. Electrochemical impedance spectroscopy measurements were carried out to distinguish the loss contributions within the system and study the degradation phenomena. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and X-ray diffraction techniques were adopted as post-experiment characterization to investigate microstructural changes and elements migration in order to confirm the observed changes in performances.
Water Splitting on Model-Composite La0.6Sr0.4FeO3-δ (LSF) Electrodes in H2/H2O Atmosphere
Authors: Opitz Alexander Karl , Nenning Andreas , Kogler Sandra , Rameshan Christoph , Rameshan Raffael , Blume Raoul , Haevecker Michael , Knop-Gericke Axel , Rupprechter Guenther , Kloetzer Bernhard , Fleig Juergen 
Published: February 2020

Solid Oxide Fuel Cells (SOFCs) attract substantial commercial interest owing to their high efficiency in generating electrical power from fuels such as methane or hydrogen. In recent years, also the research on the inverse process – the conversion of excess electrical energy in chemical energy via Solid Oxide Electrolysis Cells (SOECs) – is gaining more and more attention. As electrode on the reducing side of both SOFCs and SOECs commonly Ni/yttria stabilized zirconia (YSZ) electrodes are used but they are known to suffer from several problems, like sulfur poisoning (in SOFC operation), sintering of Ni particles, poor redox cycling stability, and coking. In contrast, mixed conducting oxide anodes are expected to exhibit improved properties.
In the present contribution the electrode kinetics of the perovskite-type mixed conductor La0.6Sr0.4FeO3-δ (LSF) is investigated in H2/H2O atmosphere by means of impedance spectroscopy and the results are compared to the polarization resistance of LSF in O2 atmosphere. To compensate for the relatively low electronic conductivity of LSF under reducing conditions a sputter deposited Pt thin film grid was used as a current collector. Interestingly, the surface resistances of these model-composite electrodes in H2/H2O and O2 at 600 °C were virtually the same indicating a high electrochemical activity of the LSF surface when operated as SOFC anode.
Moreover, synchrotron-based near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and impedance spectroscopy experiments were conducted simultaneously on electrochemically polarized LSF electrodes. Of special interest was the effect of electrochemical polarization on the composition and valence states of near surface cations of the LSF electrodes. Under cathodic polarization the formation of near-surface metallic iron was observed, accompanied by a strong improvement of the electrode’s water splitting activity [1]. This correlation of metal exsolution and electrochemical performance suggests a fundamentally different water splitting mechanism in presence of the metallic iron species and may provide new directions in the quest for novel mixed conducting SOEC cathodes for high-temperature electrochemical water splitting.
[1] A. K. Opitz et al., Angewandte Chemie International Edition 54 (2015) p. 2628-2632.

Figure 1
Evaluation of Gadolinium Doped Barium Zirconate Electrolyte for Solid Oxide Fuel Cell
Authors: de Florio Daniel Zanetti 
Published: February 2020

High proton conductivity perovskites can be utilized in many important applications. In this work gadolinium doped barium zirconate ([gadolinium oxide] = 0, 5, 10, 15 and 20% mol) was prepared by Pechini method from nitrates precursors. The powders were studied by simultaneous thermal analysis, X-ray diffraction, and scanning electron microscopy. These powders were then uniaxially pressed at 1 ton/cm2 in cylindrical discs (diameter = 10 mm and thickness ~ 1 mm) and theirs geometrical densities were determined. These pellets were sintered at temperatures of 1773 K/1 h and 1523 K/1 h with and without amounts of boric acid as sintering aid respectively, follow by geometrical and Archimedes density measurements. Phase analysis was carried out by X-ray diffraction, and fracture and polished samples surfaces were observed in scanning electron microscopy. The parallel faces of each sample was painted with platinum paste and electrical characterized by impedance spectroscopy in the frequency range from 32 MHz to 1 Hz, under static air and standard mixture (3% hydrogen/97% nitrogen) flow, in the RT up to 1273 K. The main results indicate that dense (>96 % of theoretical density) barium zirconate perovskite phase was obtained for samples liquid phase sintered with high electrical conductivity.
The Uk's First Commercially Funded SOFC Micro CHP Progarmme: Experience to Date
Authors: Cape Jon 
Published: February 2020

Over a three year period iPower has developed and now launched the UK’s first commercially funded fuel cell micro CHP programme. This utilises the SOFC based BlueGEN product. From current information this is also a world first in providing FC CHP free of charge to the user on a commercial basis.
This is not an academic paper. It is a practical paper sett9ng out experience to date with this live commercialisation process.
The presentation will set out key challenges, success factors and learning points from deployment to date under the programme and prospects for future development. It will include independent third party data and case study material.
Utilisation of Coal in Direct Carbon Fuel Cells
Authors: Irvine John , Fuentes Cuesta Aida , Mottram Andrew , Jiang Cairong , Savaniu Cristian , Jain Sneh 
Published: February 2020

Hybrid Direct Carbon Fuel Cells merge Solid Oxide Fuel Cell (SOFC) and MCFC technologies, using a solid oxide electrolyte to separate the cathode and anode compartments, while a molten carbonate electrolyte is utilised to extend the anode/electrolyte region. Oxygen is reduced to O2- ions at the cathode and transported across the solid electrolyte membrane to the anode compartment, where carbon is oxidised to CO2. Molten carbonate could enhance the carbon oxidation in two ways as a fuel carrier or as an electrochemical mediator. The maximum energy density can be achieved by fully oxidising carbon to CO2 offering very high efficiencies. This concept has been demonstrated using a wide range of carbons and carbon-rich fuels such as coal, plastics, carbon colloids, activated carbons and charcoals. In a short stack of 3 cells delivered a maximum power output at 650oC of 5.4 W, at over 100mWcm-2.
The underlying chemical processes in DCFCs are complex involving a series of catalytic and electrochemical reactions of a complex fuel. Coal and biochars are quite far from pure carbon comprising of high hydrogen content and often significant oxygen, sulphur and nitrogen contents as well as inorganic, ash components. Here we report on the pyrolysis and oxidation reactions and processes that occur in situ and in DCFC relevant conditions. Of key importance is interplay between carbon and its oxides as direct oxidation of carbon to carbon dioxide delivers the ultimate efficiency. There is a change in process above 750oC where the reverse Boudouard reaction becomes dominant and our focus is on understanding the lower temperature electrochemical processes.
Direct Coal Oxidation in Modified Solid Oxide Fuel Cells
Authors: Deleebeeck Lisa , Gil Vanesa , Ippolito Davide , Campana Roberto , Hansen Kent Kammer , Holtappels Peter 
Published: February 2020

Solid oxide fuel cells are fuel flexible in the sense that they can convert a variety of fuels into electricity because of the use of an oxygen ion conducting electrolyte. Traditional solid oxide fuel cells utilize gaseous reactants, such as hydrogen and carbon monoxide, derived from hydrocarbon based fuels, but also ammonia has been reported. A challenge is still the application of this type of cell for the conversion of solid, carbon containing fuels such as coal or biomass derived carbon in terms of pyrolized wood , e.g. charcoal (direct carbon fuel cell (DCFC)). However, several high power densities based on carbon as fuel have been reported for so called hybrid solid oxide fuel cells.
Hybrid direct carbon fuel cells may employ a classical solid oxide fuel cell e.g. using Ni-cermet anodes together with carbon dispersed in a carbonate melt on the anode side. In a European project, the utilization of various coals has been investigated with and without addition of an oxidation catalyst to the carbon-carbonate slurry or anode layer.
The nature of the coal and the catalyst composition affect both open circuit voltage and power output. Highest open circuit potentials and power densities were observed for bituminous coal and by adding manganese oxide or praseodymium-doped ceria to the carbon/carbonate mixture. Comparing the performance of an anode supported (315 micron thick anodes) and cathode supported cells (15 micron thick cathode) indicates a superior performance of the latter cell type when using carbon black as carbon source. Using biomass derived carbon (charcoal) as fuel without an additional catalyst resulted in an open circuit voltage of 984 mV and a maximum power density of 121 mW/cm2, similar to the power output of bituminous coal and using ceria or manganese based catalysts.
Further outlook on the kinetics of the carbon oxidation processes occurring in the vicinity of the anode of these cells will be provided.