bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Oxidation of CO/H2 Mixtures on Ni and Ceria Pattern Anodes
Authors: Tabish A.N. , Patel Hrishikesh C , Comelli Filippo , Aravind P.V. 
Published: February 2020

In many proposed applications of SOFC, the syngas, primarily containing CO and H2, will be fed directly to the anode. Therefore, the understanding of electrochemical co-oxidation of CO/H2 fuel is very important for designing fuel cell systems and their long term operation. Pattern electrodes with well-defined geometrical electrode/electrolyte interface have been successfully applied as a tool to study the electrochemical oxidation mechanisms at triple phase boundary (TPB).
So far, Ni/YSZ cermet anodes have mostly been used to study CO/H2 co-oxidation and Ni pattern anodes to study elementary reaction mechanisms of CO and H2. Recently, ceria based anodes are becoming of potential interest because of their ability to suppress carbon deposition on electrodes besides other advantages of ceria over conventional Ni based anodes. Ceria has widely been used for preferential oxidation of CO in automotive industry. However, only limited experimental data is available for electrochemical oxidation CO/H2 mixtures on ceria.
In this study, electrochemical oxidation of dry CO/H2 mixtures on symmetrical Ni and ceria pattern anodes on YSZ electrolyte has been examined between 700-850 oC. Regardless of the mixed ionic and electronic (MIEC) nature of ceria, ceria patterns were prepared for comparison with Ni pattern anodes with the same geometrically defined TPB length. Dry environment was used to exclude the possible side reactions like water gas shift in case of CO and CO/H2 mixtures.
Spectra obtained from electrochemical impedance spectroscopy (EIS) of Ni and ceria anodes for different gas environments at 800 oC are shown in figure. EIS with Ni anodes revealed 2-3 times higher polarization resistance for pure CO as compared to pure H2. The addition of small quantities of H2 in CO decreased the polarization resistance drastically, indicating negligible contribution of CO oxidation for total current production.
With ceria electrodes the polarization resistance was 5-6 times higher in case of CO as compared to pure H2. For all considered CO/H2 mixtures the polarization resistance was closer to that of pure H2 indicating preferential oxidation of H2 which is contrary to the expected role of ceria catalyst for preferential oxidation of CO as observed in case of non-electrochemical oxidation.
Impedance spectra from both Ni and ceria pattern anodes were fitted to the equivalent circuit model [R(RQ)(RQ)]. In all impedance spectra with ceria patterns, a small arc at high frequency was observed as compared to main arc at low frequency. Relaxation frequency of small arc was much higher as compared to the main arc. Activation energies for both Ni and ceria anodes were also similar to that of pure hydrogen for all considered mixtures further indicating preferential oxidation of hydrogen.

Figure 1
Modelling and Prediction of the Deformation during Co-Sintering of a High Temperature Dual Membrane Fuel Cell
Authors: Masson David , Kuoh-Moukouri Joyce , Chesnaud Anthony , Thorel Alain 
Published: February 2020

In the frame of a FP7 project (FET-Energy “IDEAL-Cell”, 2008-2011), we have developed with a European consortium a new type of high temperature fuel cell based on a dual membrane with mixed proton and oxygen ions conductivity. This dual conductivity porous membrane, made of a proton conducting phase (BCY15) and of an oxygen conducting phase (YDC15) was sandwiched between a dense BCY15 electrolyte and a dense YDC15 second electrolyte, forming a tri-layer itself sandwiched by a cathode (LSCF48) and an anode (BCY15 + Ni). In this configuration, water is formed neither at the cathode nor at the anode, minimizing electrodes concentration overpotentials, but rather within the dual membrane which interconnected porosity ensures water evacuation. The IDEAL-Cell project i) proved the concept, ii) showed that this new fuel cell was performing better at 750°C than PCFCs and SOFCs having equivalent thickness, iii) showed that the concept was fully reversible with a high dynamic when shifting from the fuel cell regime to the electrolyzer regime, iv) showed that BCY15 was also an excellent oxygen ions conductor when fed with oxygen, and then demonstrated that the cell could be fabricated by using solely BCY15 (replacing YDC15 in the dual membrane and for the oxygen electrolyte), leading to a drastic simplification of the concept, hence of the shaping process.
Today, this simplified cell is fabricated at the laboratory scale by a sequence of successive steps (1/ cold pressing, rolling and sintering of the porous dual membrane at 1350°C, 2/ deposition of both electrolytes by dip coating, and sintering at 1350°C, 3/ deposition of both cathode and anode by bar-coating, and sintering at 1150°C), which is hardly cost effective in view of stacking and further development. The present work proposes to demonstrate that co-sintering of the whole cell in a single step is possible, and to determine under what conditions of geometry, starting materials and sintering cycle a flat and stress-free cell in view of stacking, efficiency and durability can be produced via this simplified process. The research described in this paper was based on the thermomechanical modelling of the multilayer deformation occurring during sintering via a finite element numerical simulation, in which debinding, elastic and irreversible deformations, kinetics of grain growth and pores shrinkage are integrated. The thermomechanical parameters were obtained on a differential CTE measurement set-up, and the microstructural ones by image analysis on SEM images.
3D Multiscale-Multiphysics SOFC Modelling Status at the Institute of Electrochemical Process Engineering, FZ Jülich
Authors: Peksen Murat , Al-Masri Ali , Peters Roland , Blum Ludger , Stolten Detlef 
Published: February 2020

The Institute of Electrochemical Process Engineering (IEK-3), SOFC modelling research group has been focusing on the 3D multiphysics modelling of SOFCs [1], auxiliary components [2-4], as well as whole fuel cell systems [5] during the last seven years; thereby giving particular attention to various geometrical scales including, micro, meso and macro level of solid oxide fuel cells [6-9], as well as cell, stack and system level high-end modelling.
Currently, emphasis of research has been given to the material, process and 3D design optimisation of APU fuel cell stacks, including the thermomechanical behaviour during the heating-up, operation and shut-down stages for safe SOFC operation. Micro modelling of cells, including the thermomechanical fatigue behaviour has been another research area to understand the cyclic durability of the critical fuel cell stack regions.
The full scale 3D system level multiphysics modelling of the Forschungszentrum Jülich integrated SOFC system has been successfully continued and important results have been achieved and experimentally validated to improve the knowledge about the overall multiphysics system in full detail. Moreover, the interacting component behaviour of the fuel cell stack, afterburner, heat exchanger, pre-reformer and baffle plates have been intensively investigated to improve their design and thermofluid flow, thermomechanical performance. Coupled CFD/FEM is used to predict their thermofluid flow, heat radiation, electrochemical and chemically reacting species transport, creep, elastoplasticity and cyclic behaviour.

M. Peksen, Progress in Energy and Combustion Science, 48, 1-20 (2015)

M. Peksen, L. Blum and D. Stolten, Int. J. Hydrogen Energy,
37, 12540-12547 (2012)

Q. Fang, L. Blum, R.Peters, M. Peksen, P. Batfalsky, D.Stolten, Int. J. Hydrogen Energy
2, 1128-1136 (2015)

M. Peksen, Ro. Peters, L. Blum, D. Stolten, Int. J. Hydrogen Energy,
36
, 6851-6861 (2011)

A. Al-Masri, M.Peksen, L.Blum, D. Stolten Applied Energy, 135, 539-547 (2014)

M. Peksen, Int. J. Hydrogen Energy, 39, 5137 (2014).

M. Peksen, Int. J. Hydrogen Energy, 38, 13408-13418 (2013)

M. Peksen, Int. J. Hydrogen Energy, 36, 11914 (2011).

M. Peksen, A. Al-Masri, L. Blum and D. Stolten, Int. J. Hydrogen Energy,
38, 4099 (2013).
Effect of Non-Uniform Electrode Microstructure in Gas Diffusion Impedance
Authors: Bertei Antonio , Arcolini Giacomo , Nicolella Cristiano , Piccardo Paolo 
Published: February 2020

Gas diffusion resistance represents a significant contribution to anode overpotential in anode-supported solid oxide fuel cells (SOFC). Gas diffusion limitations are often detected through the analysis of impedance spectra. Typically, equivalent circuits are adopted to fit the measured impedance data. However, equivalent circuits do not account for the non-uniform microstructure of SOFC anodes, which commonly consist of a fine functional layer and a thicker and coarser supporting layer.
In this study, the impedance response of gas diffusion phenomena in anodes with non-uniform microstructure is simulated by solving the dusty-gas model in frequency domain. The microstructural parameters are evaluated from the tomographic reconstruction of the two layers, as published in the literature. Simulations indicate that the non-uniform electrode microstructure affects the gas diffusion dynamics, thus producing an additional feature in the Nyquist plot at high frequency. Such an additional feature may be erroneously attributed to other phenomena (e.g., charge transfer processes) when phenomenological equivalent circuits are superimposed to fit the data.
The study shows that the gas diffusion fingerprint in impedance spectra can substantially differ from the expected finite-length Warburg response in electrodes with non-uniform microstructure. The paper highlights the potential misinterpretations that can arise when interpreting impedance spectra with phenomenological models, especially when the coupling between microstructural characteristics and electrode dynamics are not properly taken into account.
Computational Materials Design of Rare-Earth-Based Fast Oxygen Ion Conductors by First-Principles Simulation Based on Density Functional Theory
Authors: Sakaue Mamoru , Kasai Hideaki 
Published: February 2020

Development of novel fast ion conductors is a crucial issue for realizing solid oxide fuel cells (SOFCs) which can operate in low temperatures. While yttria-stabilized zirconia (YSZ) had been well-studied both by experiments and theories, exploration of other types of materials retaining high ionic conductivities in lower temperatures is still desired. Experimental studies in the recent twenty years have found some rare-earth-based oxides having higher ionic conductivities to be promising for operation below 600°C [1-4], and first-principles simulation studies on the materials have begun [5-9]. As well as doping, introduction of strain by forming a laminate of nanoscale films was found to be an effective factor for controlling ionic conduction [3,5].
We studied atomic and electronic properties on oxygen-ionic conduction of LaGaO3-, La2GeO5-, Pr2NiO4- and CeO2-based materials by first-principles calculations based on density functional theory (DFT). We analyzed effects of doping and strain on stable structures, electronic densities of states, oxygen migration paths and activation energies in order to evaluate their capabilities in application to electrolytes. We focus on minimum energy paths of oxygen migration based on nudged elastic band analysis in order to figure out ion conduction properties in low temperatures. The obtained simulation results of the activation energies showed good agreements with experiments in several aspects. By analyzing the site dependencies of vacancy formation energies and activation energies, we inferred possible factors of preventing the oxygen ion conduction.
Based on the results, we practiced iterative materials design procedures that we deduced possibly more promising compositions for the oxygen ion conduction, confirmed the properties by simulation, inferred the desirable and undesirable factors, and went back to the deduction of possibly more promising compositions. In the presentation, we will propose the designed materials and predict their electronic, magnetic and ion conduction properties.

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Evaluating the Behavior of CO/CO2 in Ni/GDC Solid Oxide Fuel Cell Anodes
Authors: Wang Lei , Jackson Gregory S 
Published: February 2020

Ni/GDC anodes for solid oxide fuel cells have been reported to be more resistant to carbon deposition than conventional Ni/YSZ anodes. To facilitate understanding the nature of carbon chemistry in Ni/GDC anode functional layers, we have studied the behavior of CO oxidation and CO2 dissociation on thin-film Ni/GDC electrodes. Sputtered thin-film GDC electrodes with open Ni sputtered overlayers provide an optically accessible and well-characterized electrode in which to study fundamental reactions of CO and CO2 in Ni/GDC systems for both dry and wet environments. To further separate out the behavior of the GDC surface chemistry from the Ni chemistry, Au overlayers were deposited on the thin-film GDC for an alternative electrode with the Au serving as a low-activity current collector. Results indicate that dry CO oxidation and CO2 dissociation are substantially slower than their H2 and H2O analogs on Ni/GDC with fitted exchange current densities for CO/CO2 approximately one order of magnitude lower than H2/H2O under similar partial pressures and temperatures ranging from 600 to 700 deg. C. By replacing the CO2 with H2O, exchange current densities associated with CO oxidation rise dramatically although still lower than H2 oxidation at similar conditions. By using our studies with ambient pressure XPS, we are able to obtain local overpotentials across the Ni/GDC for some test conditions and thereby extract fundamental information about the CO and CO2 chemistry in the Ni/GDC cell.
Although the CO/CO2 reactions are slow, they may play a vital role in the suppression of carbon formation in Ni/GDC cells. Thus, to better understand this, we fit our experimental data for the thin-film electrodes to a microkinetic model that includes CO/CO2 chemistry on both the Ni and GDC. By fitting these rates to match the model results to the performance of Ni/GDC and Au/GDC electrodes (and assuming the Au functions as an inert current collector), we have developed kinetic expressions for surface chemistry of CO and CO2 on the GDC surface. Coupling this surface chemistry to previous Ni surface chemistry and to our own developed mechanism for H2 oxidation on Ni/GDC provides a basis for exploring how the Ni and GDC surface chemistry interact with exposure to carbon-rich syngas. The fitted model for the thin-film Ni/GDC performance suggests that the presence of surface hydrogen and hydroxyls on the Ni can have significant boosts to CO conversion to CO2 on both the GDC and Ni surfaces. These synergies may be critical for providing rapid CO conversion in lower temperature SOFCs which rely on GDC as part of the anode and electrolyte materials.
Enhancing the Stability of Infiltrated Ni/YSZ Anodes
Authors: Keyvanfar Parastoo , Hanifi Amir Reza , Sarkar Partha , Etsell Thomas H. , Birss Viola 
Published: February 2020

One of the challenges related to Ni-based anodes in solid oxide fuel cells (SOFCs) is their dimensional instability, especially when they are exposed to air and then back to fuel, which is called redox cycling. One possible solution to this problem is the fabrication of a pre-sintered porous electrolyte matrix, followed by infiltration of 10-20 vol% of the active materials into this scaffold. However, this can lead to instability of the infiltrated particles as a result of sintering of the infiltrated phase at SOFC working temperatures. This problem is very severe when depositing nano-sized infiltrated metal particles on the oxide ceramic backbone.
In this study, Ni-containing solutions were infiltrated into a symmetrical tubular half-cell, fabricated by slip-casting, composed of two porous yttria-stabilized zirconia (YSZ) layers, separated by a 50 μm dense YSZ electrolyte. A combination of electrochemical impedance spectroscopy (EIS) and electron microscopy imaging has been used to determine long term stability of the cells.
It was found that the amount of infiltrated Ni has a significant impact on the long term stability of the Ni/YSZ anodes. This can be explained by the better connectivity between Ni particles even after long term testing when there is more Ni in the structure. It was also demonstrated that high temperature treatment of the infiltrated Ni/YSZ anodes just after the first few infiltrations, followed by several further Ni infiltration steps, has a significant effect not only on the stability of the anode at 800 C, but also on the anode performance. As the YSZ backbone has the ability to dissolve NiO at higher temperatures, the dissolved NiO can be ex-soluted in the form of nano-sized Ni particles at cell working temperatures and under reducing atmospheres. This effect was also investigated using electron microscopy, revealing the size and shape of the ex-soluted Ni particles, especially after long term testing.
Finally, the effect of infiltration of cerium oxide prior to Ni infiltration on the stability of the anodes was also investigated. As the wettability of Ni particles on a reduced ceria surface is different from non-reduced ceria, the sintering behaviour of Ni on these two surfaces was found to be different as well.
Direct Utilization of Methane in Microtubular-SOFC
Authors: Majewski Artur Jacek , Dhir Aman 
Published: February 2020

Microtubular-SOFC (μSOFC) offer many advantages over planar SOFC systems. They offer greater resistance to thermal shock, allow rapid startup and shut down. They have high volumetric power density and the seals can be placed out of the high temperature zone. Liquefied natural gas (LNG) is receiving increased interest as a fuel for trucks. This is an ideal fuel for SOFC. In this paper we examine the use of LNG in μSOFC in a truck APU application and the issues associated with LNG fuel. The work mainly focuses on solving issues with temperature distribution along and across the cell.
The key problem in the proposed system is the temperature distribution (TD). Despite the good resistance to thermal shock, the long-term operation with unequal TD can cause cell damage. The TD was measured along the cell (internally and externally) under different operating conditions. H2, CH4 and simulated LNG (individual gases mixed in the correct ratio of LNG) were used as fuels. CH4 and simulated LNG were converted into syngas using semi-internal catalytic partial oxidation catalyst (CPOX) located at the entrance of the cell. Different mixtures of fuel and air and several different catalysts were tested for the CPOX of hydrocarbons. The figure shows a typical result during OCV using H2 as a fuel at 700oC furnace temperature. It shows there was a difference of 200oC between the internal and external part of the tube at the fuel inlet, indicating research needs to be conducted into minimising this to ensure the durability of any SOFC APU system.
Figure 1. Temperature distribution inside the μSOFC single cell.
The results are part of the SAFARI project funded under Europe’s Fuel Cell and Hydrogen Joint Undertaking (FCH JU), Grant Agreement No.325323. The Consortium gratefully acknowledges the support of the FCH JU.

Figure 1
Performance Factors and Sulfur Tolerance of Metal Supported Solid Oxide Fuel Cells with Nanostructured Ni:GDC Infiltrated Anodes
Authors: Nielsen Jimmi , Sudireddy Bhaskar Reddy , Hagen Anke , Persson Åsa Helen 
Published: February 2020

In recent years, there has been a growing interest in developing metal supported solid oxide fuel cells (MS-SOFCs). MS-SOFCs are interesting as they potentially offer some advantages compared to conventional electrode and electrolyte supported SOFCs, such as low materials cost, better thermal conductivity and ductility of the support. The two later aspects improve the shock resistance and lower internal gradients within the stacks. This enables fast start-up and provides higher tolerance towards operation under transient conditions that are particularly desirable for APU applications.
Today’s commercially available and relevant SOFC fuels such as natural gas and diesel etc. contain trace amounts of sulfur. Thus, tolerance towards sulfur poisoning is desirable. Ceria and gadolinium doped ceria (GDC) have been reported in the literature to have a beneficial effect on the tolerance towards sulfur poisoning. The ceria can be incorporated as a Ni:GDC cermet anode, but also via infiltration of ceria and doped ceria into the conventional Ni:YSZ cermet anode. Both approaches have been reported to improve the tolerance towards sulfur poisoning [1-3]. In the present study we report the performance and sulfur tolerance of MS-SOFCs with two different microstructures of the support and the anode functional layer (AFL). The MS-SOFCs of the present study are based on ferritic stainless steel (FeCr) with an aimed operating temperature of 650ºC. This lower operating temperature compared to electrode and electrolyte supported SOFC (750ºC-850ºC) is expected to favor sulfur adsorption and hence increase the impact of sulfur poisoning. The AFL was infiltrated with Ni-GDC precursor solution and subsequent heat treated resulting in a nanostructured coating of the electrocatalyst. The two studied MS-SOFC single cells (active area 16 cm2) have initial area specific resistances (ASR) at 650ºC of 0.35 Ωcm2 and 0.7 Ωcm2 respectively. It was found that the porosity of the support and the AFL seems to have a pronounced effect on the resulting performance. The MS-SOFCs were subjected to technologically relevant H2S concentrations of 2, 5 and 10 ppm in hydrogen fuel, during galvanostatic operation at a current load of 0.25 Acm-2. The results are illustrated and compared with the conventional SOFC Ni:YSZ cermet anode in figure 1, where the relative increase in anode polarization resistance as a function of Ni sulfur coverage is shown. The comparison indicate the MS-SOFC anode of the present study to be more tolerant towards sulfur poisoning than the conventional Ni:YSZ cermet anode.
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[3] C. Xu, P. Gansor, J. W. Zondlo, K. Sabolsky, and E. M. Sabolsky, J. Electrochem. Soc., 158, B1405–B1416 (2011).

Figure 1