Publications de Stefan Diethelm

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Electrochemical Impedance Spectroscopy (EIS) is extensively used to characterize Solid Oxide Cells (SOCs) to extract information on the elementary loss mechanisms. However, these individual mechanisms usually overlap in the frequency domain, requiring dedi ...

Power-to-fuel systems via solid-oxide electrolysis are promising for storing excess renewable electricity by efficient electrolysis of steam (or co-electrolysis of steam and CO2) into hydrogen (or syngas), which can be further converted into synthetic fuel ...

Power-to-methane technologies have been regarded as a promising alternative to offer small or large-scale, long-timescale (daily/weekly/seasonal) energy storage as well as the opportunity of utilizing CO2. The performance of the core component, the electro ...

A rigorous mathematical model is developed for the complex impedance of a solid-state electrochemical cell, which is commonly used for the measurement of oxygen transport, oxygen exchange kinetics and thermodynamic properties of nonstoichiometric mixed conducting oxides. The model leads to a simple equivalent circuit for the cell with unambiguous definition of the physical significance of its components. A method is proposed for the analysis of experimental data. The methodology thus developed is validated

The degradation of the electrochemical performance of solid oxide fuel cell (SOFC) devices is a major hurdle to overcome before commercialisation. The interplay between the phenomena and the long testing times complicate the research, which highlights the ...

The content of this report is property of HTceramix and subject to restrictive distribution The goal of the project "Oxygen membranes for the partial oxidation of natural gas" was the pre-industrial evaluation of the concept of an electroceramic reactor, capable of converting natural gas into synthesis gas (H2+CO) by partial oxidation with pure oxygen. This project was the continuation of the pre-project on the fundamental principle (FOGA 085) accomplished with success at EPFL and which was co-financed by F

Researchers and developers typically use I-V curves (current vs. potential) as a means to demonstrate good data fitting of a model under experimental validation. Despite the popularity of this method, assessment of the results can be intuitive rather than mathematical, and usually, when such a demonstration occurs, information on the quality of the parameter estimation is not given. On the contrary, it has been shown that simple model fitting on I–V curves cannot give statistically reliable results on the v

The aim in this project was the optimization of LaFeO3-based perovskite materials for oxygen separation membranes (OSM). The work was carried out by the Laboratory for High Performance Ceramics, Empa in collaboration with the Laboratory for Industrial Energy Systems, LENI, EPFL and the Ceramics Laboratory, LC, EPFL. The ceramic material of interest is a mixed conductor for oxygen ions and electrons at high temperature (800°-900°C) and therefore can separate oxygen from nitrogen with 100% selectivity when

Reversible solid oxide cells (rSOC) can convert excess electricity to valuable fuels in electrolysis cell mode (SOEC) and reverse the reaction in fuel cell mode (SOFC). In this work, a five - cell rSOC short stack, integrating fuel electrode (Ni-YSZ) suppo ...

This paper presents a model-based investigation to handle the fundamental issues for the design of co-electrolysis based power-to-methane at the levels of both the stack and system: the role of CO2 in co-electrolysis, the benefits of employing pressurized ...

Solid Oxide Fuel Cell systems (SOFC) are developed for their electrical efficiency and versatility. Versatility stems from their tolerance towards CO and CH4, which allows for the use of various reformed fuels. Efficiency results from the direct conversion of the chemical energy of fuels into electricity and the availability of high temperature heat for internal steam reforming. In this study, short SOFC stacks provided by SOFCpower were tested under methane steam reforming conditions. The stacks were coupl

This study investigates the performance of a standard Ni-YSZ anode supported cell under ethanol steam reforming operating conditions. Therefore, the fuel cell was directly operated with a steam/ethanol mixture (3 to 1 molar). Other gas mixtures were also u ...

High-temperature electrolysis for reducing H2O (and CO2) to H2 (and CO) converts concentrated solar energy into fuels and chemical feedstock. We invented an integrated reactor concept comprising a solar cavity receiver for reactant heating, a solid oxide e ...

A solid oxide short stack composed of 6 Ni-YSZ supported cells, YSZ electrolyte and GDC-LSC oxygen electrode has been tested for 10,700 hours in steam electrolysis. Initial degradation was followed by a global stabilization of the performance after lowerin ...

Oxygen permeability through the tubular La0.7Ca0.3Fe0.85 Co0.15O3-δ perovskite membrane prepared by thermoplastic extrusion was measured in the temperature range from 800° to 1040°C in an air/argon gradient, and compared with the oxygen permeability of pla ...

Solid-oxide electrolyzer based power-to-methane is promising for large-scale energy storage as well as biogas upgrading by efficiently converting intermittent renewable power and CO2 (e.g., in biogas) into synthetic methane. Either air or pure oxygen can b ...

Oxygen diffusion is treated in a dense electronically conducting cobaltate pellet blocked ionically on one surface, electronically on the other, and sealed on its cylindrical periphery. A procedure is developed for extracting the chemical diffusion and surface exchange coefficients for oxygen by use of the asymptotic equations derived for the current response to a potential step at short and long times. It is shown that, while the formation of interfacial phases by reaction between the sample and the electr

Lifetime prediction and improvement of solid oxide fuel cell (SOFC) devices require a reliable electrochemical model that supports the implementation of degradation phenomena. This study comprises two parts. This Part I describes the calibration of an elec ...

The objective of the current work is to support the design of a pilot hydrogen and electricity producing plant that uses natural gas (or biomethane) as raw material, as a transition option towards a 100% renewable transportation system. The plant, with a s ...

In this study, two short SOE stacks (6-cells) were characterized in steam-electrolysis mode. The first was based on Ni-YSZ supported cells with LSCF-based air electrodes. The second included LSC-based air electrodes specifically developed within the SOFC60 ...

Stefan Diethelm

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Model-assisted identification of solid oxide cell elementary processes by electrochemical impedance spectroscopy measurements

Power-to-fuels via solid-oxide electrolyzer: Operating window and techno-economics

Optimal design of solid-oxide electrolyzer based power-to-methane systems: A comprehensive comparison between steam electrolysis and co-electrolysis

Determination of Chemical Diffusion and Surface Exchange Coefficients of Oxygen by Electrochemical Impedance Spectroscopy

Electrochemical model of solid oxide fuel cell for simulation at the stack scale. Part II: Implementation of degradation processes

Realization of a reactor for the partial oxidation of natural gas to syngas based on oxygen separation ceramic membranes - proof of concept

A Parameter Estimation Method for Fuel Cell Diagnostics

Optimization of mixed conducting perovskites for the application in dense ceramic oxygen separation membranes, used in partial oxidation of natural gas to synthesis gas

Degradation study of a reversible solid oxide cell (rSOC) short stack using distribution of relaxation times (DRT) analysis

Power-to-methane via co-electrolysis of H2O and CO2: The effects of pressurized operation and internal methanation

Performance of SOFC stacks under partial internal reforming of methane

Ethanol internal steam reforming in intermediate temperature solid oxide fuel cell

Integrated solar-driven high-temperature electrolysis operating with concentrated irradiation

Post-test Analysis on a Solid Oxide Cell Stack Operated for 10,700 Hours in Steam Electrolysis Mode

Tubular La0.7Ca0.3Fe0.85 Co0.15O3-δPerovskite Membranes, Part II: Performance and Stability

Trade-off designs of power-to-methane systems via solid-oxide electrolyzer and the application to biogas upgrading

Simultaneous determination of chemical diffusion and surface exchange coefficients of oxygen by the potential step technique

Electrochemical Model of Solid Oxide Fuel Cell for Simulation at the Stack Scale I. Calibration Procedure on Experimental Data

Design of a Pilot SOFC System for the Combined Production of Hydrogen and Electricity under Refueling Station Requirements

Electrolysis and Co-Electrolysis Performance of SOE Short Stacks