Publications by Stefan Diethelm

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In order to characterize a new SOFC stack design, to investigate degradation processes and to validate models, a diagnostic test station was designed and realized. It allows to characterize repeat-elements locally by measuring the local potential, current density and temperature over the active area. The active area is segmented in 18 small electrically insulated measurement points (segments), in addition to a main segment. The profile of current density was investigated up to an average of 0.6A/cm2 and 67%

We present a SOFC stack technology based on the unique SOFConnex™ concept. It uses flexible gas distribution layers between metal sheet interconnects and thin ASE cells (Ni-YSZ anode supported, thin electrolyte). Flexibility is given both in material and d ...

The effect of the bulk microstructure (grain size distribution, grain boundary composition on the oxygen transport properties of La0.5Sr0.5FeO3membranes was investigated. For this purpose, samples with different microstruct ...

(La,Sr)FeO3 mixed conducting perovskites are considered as interesting candidates for oxygen separation membranes but they suffer from limited structural stability in a large oxygen partial pressure (pO2) gradient, because of their propensity for chemical ...

The present paper investigates the variation in performances in steam electrolysis and co-electrolysis of steam/CO2 on SOEC single cells.In electrolysis mode, a sensitivity analysis was performed looking in particular at the effects of temperature (750°C a ...

The effect of the bulk microstructure (grain size distribution, grain boundary length) on the oxygen transport properties of permeation membranes is investigated in this work. For this purpose, La0.5Sr0.5FeO3-? samples with different microstructures have been prepared by modifying the sintering duration and/or temperature. The average grain sizes, ranging from 0.20 to 1.43 micron, were determined from SEM analysis. The oxygen transport properties of these samples were characterised by permeation measurement

Our planar SOFC stacking technology uses unprofiled metallic interconnects (MIC) and thin cells of tape cast anode supported YSZ. The key element is the gas diffusion layer (GDL) between cell and MIC, which consists of so-called SOFConnex™. Using square ce ...

Although the effects of impurities on the Ni-YSZ electrode of a solid oxide cell in fuel cell operation have been studied, reports on their effects during electrolysis operation are limited. Here, short-term experiments at various current densities and a d ...

Correlating the microstructure of an energy conversion device to its performance is often a complex exercise, notably in solid oxide fuel cell research. Solid oxide fuel cells combine multiple materials and interfaces that evolve in time due to high operat ...

Electrochemical techniques were applied to a coulometric titration cell to study oxygen nonstoichiometry and transport in the perovskite-type oxide La0.4Ba0.6Fe0.8Co0.2O3-delta. Slow scan voltammetry (3mV/s) was used to obtain oxygen nonstoichiometry vs. the oxygen partial pressure (p(O2)) data. The voltammograms were further analysed using a simple defect model to yield the absolute value of the oxygen nonstoichiometry. Relaxation measurements were performed to obtain chemical diffusion and surface exchang

This paper reports on medium term tests of anode-supported five-cell short stacks, as well as on some separate anode development. Two stacks were operated under steady-state conditions: one with unprotected metal interconnects, H-2 fuel and 0.35 A cm(-2) ( ...

Three perovskite-type compounds of composition La0.4Ca0.6Fe1-xCoxO3-d (x=o, o.25 and 0.5) were investigated for use as oxygen separation membranes for the partial oxidation (POX) of methane to syngas. Special attention was given to the question of their stability in real operating conditions. A permeation set-up was specially designed to measure oxygen fluxes through these materials when placed in a strong pO2 gradient. It also facilitated testing the long-term stability of the specimen. Permeation measurem

Dense planar and tubular oxygen separation membranes of La 0.6Ca0.4Fe0.75Co0.25O3-d were investigated as reactors for the partial oxidation (POX) of methane to syngas. Disk-shaped membranes were prepared by compaction and tubes by extrusion. Their permeation properties were measured in an air/argon pO2 gradient as a function of temperature. At 900°C, the oxygen flux through a 1.26 mm thick membrane was 0.075 micromol/cm2s and through a 0.25 mm thick tube, 0.24 micromol/cm2s. For the POX measurements, a cata

To improve the industry benchmark of solid oxide fuel cell (SOFC) systems, we consider anode off-gas recirculation (AOR) using a small-scale fan. Evolutionary algorithms compare different system design alternatives with hot or cold recirculation. The syste ...

Dense tubular self-supporting La0.7Ca0.3Fe0.85 Co0.15O3-δperovskite membranes were prepared by thermoplastic extrusion. The rheological behavior of the ceramic mixture was studied. Non-deformed tubes o ...

A CFD model was developed to predict with accuracy the local electrochemical performance in an operating solid oxide fuel cell. A particular focus was given on the study of performance limitations and degradation sources caused by the design of the fuel cell, by the choice of materials and components, or by improper operating points. The model is used to understand typical degradation effects observed on stacks tested in collaboration with HTCeramix - SOFCpower. The model is able to predict several degradat

The locally-resolved degradation behavior was studied during 1900 hours in an SOFC repeat-element. In-situ measurements of local electrochemical performance were made on 18 locations over a segmented anode-supported cell. The evolution of local current densities, overpotentials and area-specific resistances was studied, showing a reorganization of the electrochemical reaction with time. The extent and the spatial distribution of degradation were established for different electrochemical reactions steps usin

The influence of partial substitution of Fe with Ti on the oxygen transport properties of La1- xSrxFeO3 membranes was investigated in view of their application for oxygen separation. Samples of composition La0.5Sr0.5 Fe1-yTiyO3-δ (y = 0, 0.2) were prepared ...

The triode solid oxide fuel cell (SOFC) is a three electrodes configuration. The third electrode, so-called auxiliary, is connected in a way to run in electrolysis mode, while cathode and anode operate in normal fuel cell mode. This mixed operation allows ...

Stefan Diethelm

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Investigation of Local Electrochemical Performance and Local Degradation in an Operating Solid Oxide Fuel Cell

Innovative flexible SOFC stack concept

Correlation between oxygen transport properties and microstructure in La0.5Sr0.5FeO3-δ

Improved stability of La0.5Sr0.5FeO3 by Ta-doping for oxygen separation membrane application

Steam and Co-Electrolysis Sensitivity Analysis on Ni-YSZ Supported Cells

Influence of microstructure on oxygen transport in perovskite type membranes

Design of 500 W Class SOFC Stack with Homogeneous Cell Performance

Poisoning effects of chlorine on a solid oxide cell operated in co-electrolysis

Operando analysis of a solid oxide fuel cell by environmental transmission electron microscopy

Electrochemical characterisation of oxygen nonstoichiometry and transport in mixed conducting oxides : Application to La0.4Ba0.6Fe0.8Co0.2O3

Ageing of anode-supported solid oxide fuel cell stacks including thermal cycling, and expansion behaviour of MgO-NiO anodes

Ageing of anode-supported solid oxide fuel cell stacks including thermal cycling, and expansion behaviour of MgO–NiO anodes

Oxygen permeation and stability of La0.4Ca0.6Fe1 - xCoxO3-delta (x=0, 0.25, 0.5) membranes

Planar and Tubular perovskite-type membrane reactors for the partial oxidation of methane to syngas

Modeling and Designing of a Radial Anode Off-Gas Recirculation Fan for Solid Oxide Fuel Cell Systems

Tubular La0.7Ca0.3Fe0.85Co0.15O3-delta Perovskite Membranes, Part I: Preparation and Properties

Modeling of Local Cell Degradation in Solid Oxide Fuel Cells: Cumulative Effect of Critical Operating Points

Locally-Resolved Study of Degradation in a SOFC Repeat- Element

Oxygen transport in La0.5Sr0.5Fe1-yTi yO3-δ (y=0.0,0.2) membranes

Triode Solid Oxide Fuel Cell Operation Under Sulfur-Poisoning Conditions