EU harmonised terminology for hydrogen generated by electrolysis

This report entitled EU harmonised terminology for hydrogen generated by electrolysis is prepared under the FWC between JRC and FCH2JU. It is the result of a collaborative effort between European partners from industry, research and development (R&D) organisations and academia participating to FCH2JU funded R&D projects3 in electrolysis applications. The objective of this pre-normative research (PNR) document is to present an open and comprehensive compendium of harmonised terminology which are encountered in electrolysis applications. As means of ordered knowledge representation, clarity of communication and open access to technical information, the commonly accepted terms and definitions of this compendium cover electrolysis R&I aspects. These aspects are materials research, modelling, design & engineering, analysis, characterisation, measurements, laboratory testing, prototype development and field tests including demonstration as well as quality assurance (QA). The commonly accepted definitions of terms and phrases may be used in RD&D project documents, test and measurement methods, testing procedures and protocols, scientific publications, and technical documentation. It is primarily intended for use by those involved in conducting RD&D as well as in drafting and evaluating R&I programme but also contains information which may be useful for others such as auditors, manufacturer, designer, system integrators, testing centres, service providers and educators. Note, the compendium is expandable to account for future power-to-hydrogen (P2H2) developments in energy storage (ES) particularly electrical energy storage (EES) and hydrogen-to-substance (H2X) applications.JRC.C.1 - Energy Storag

Degradation of Solid Oxide Cells During Electrolysis and Co-Electrolysis Operation

High temperature steam and co-electrolysis has a high potential for the efficient production of hydrogen or syngas. For a further development of this promising technology, development work on materials and cells as well as extensive operational experience is still needed. A main objective is to develop highly efficient and long-term stable cells and stacks using novel electrode materials and to improve the degradation behaviour by elucidating the relevant degradation mechanisms. Fuel electrode supported cells containing perovskite-type air electrodes were fabricated by ceramic processing and sintering techniques to be electrochemically characterized in electrolysis and co-electrolysis operating mode. I-V curves and electrochemical impedance spectra have been recorded for cell characterization. For a systematic investigation of the influence of relevant operating parameters such as temperature, current density and fuel gas humidification on long-term degradation a special test bench has been established which allows electrochemical characterization of 4 cells simultaneously under relevant SOEC conditions. This arrangement allows for variation of one distinct operating parameter while keeping other parameters strictly constant. A series of measurements over 1000 hours each in the temperature range 750-850 °C with different fuel gas humidity (40-80 mol%) and different current densities between 0 and 1.5 A/cm2 has been performed in steam electrolysis mode. Additionally, a second series of measurements has started in co-electrolysis mode at different operating temperatures and different steam-to-CO2 ratios. The progress of degradation was monitored in-operando approximately every 150 h by impedance spectroscopy. Post-mortem investigations have been conducted to localize and identify the limiting processes and to clarify the correlation between degradation processes and operational parameters. In this paper results of electrochemical cell characterization performed at different operational conditions in electrolysis and co-electrolysis mode are shown and degradation phenomena observed and their underlying mechanisms based on different electrochemical processes are explained

Evaluation of Performance and Degradation Profiles of a Metal Supported Solid Oxide Fuel Cell Under Electrolysis Operation

In the context of energy transition, the use of renewable energies through the conversion of different resources with promising technologies into storable energy carriers is of eminent importance for a sustainable energy supply. Hydrogen production from steam using solid oxide electrolysis cells (SOEC) is part of this so called “energy mix”. Recently, promising progress appeared from the investigation of metal supports in the solid oxide cell architecture. Metal-supported solid oxide fuel cells (MS-SOFCs) show not only good mechanical strength, relatively low operating temperature (500-750°C) and improved sealing capability but also low materials cost and tolerance towards rapid thermal cycling and redox cycling (1-3). In the present study, a MS-SOFC was tested under electrolysis conditions. The cell consisted of Ni-catalyst loaded La0.1Sr0.9TiO3-α/gadolinium-doped ceria (Ni-LST/GDC) as fuel electrode, gadolinium-doped ceria / yttrium-stabilized zirconia (GDC/YSZ) as electrolyte and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) as O2 electrode. The cell was first tested in fuel cell mode under different gas compositions. Subsequently, a first evaluation of the cell performance profile in electrolysis mode was performed. Thus, a series of current-voltage curves as well as impedance diagrams (under OCV and under load) was recorded. Furthermore, degradation under electrolysis operation was also investigated based on the evolution of the cell voltage against time

In situ diagnosis tool based on electrochemical impedance spectroscopy for the study of high temperature solid oxide electrolyzers

Un outil de diagnostic in situ pour l'étude des électrolyseurs à oxyde solide, fondé sur la spectroscopie d'impédance électrochimique, a été mis en place à travers une analyse systématique de l'influence de plusieurs paramètres (densité de courant, température, composition et débit des gaz) sur les performances et le comportement d'une monocellule commerciale dans une configuration à 2 électrodes. Les principaux phénomènes régissant le fonctionnement de la cellule ont été identifiés. Une analyse de son comportement après apparition et évolution dans le temps d'une dégradation prématurée, suite à une modification sur le banc d'essai, a été réalisée. Un mécanisme expliquant l'origine et les conséquences de cette dégradation prématurée a été proposé. Une étude sur l'influence de l'épaisseur d'une des deux électrodes de la cellule a par ailleurs permis de distinguer deux des phénomènes principaux liés à la diffusion de H2O à l'électrode Ni-YSZ. Enfin, l'étude du comportement de la cellule après dégradation par conduction électronique de l'électrolyte YSZ a mis en évidence la formation de porosités entrainant notamment des délaminations à l'interface YSZ/YDC. Un état de dégradation plus avancé que pour les tests précédents a été observé pour les couches YDC et Ni-YSZ. Ce phénomène se manifeste par un déplacement en fréquence de l'ensemble du diagramme d'impédance mesuré vers les plus basses fréquences, formant une boucle négative. Rp finit par disparaitre, le courant circulant alors majoritairement via la conduction électronique de l'électrolyte YSZ.An in situ diagnosis tool, based on electrochemical impedance spectroscopy, for the study of solid oxide electrolyzer cells was established through the analysis of the influence of several parameters (current density, temperature, gas composition and gas flow rate) on the performances and the behavior of a commercial single cell studied in a two-electrode configuration. The main phenomena governing the cell were identified. An analysis of its behavior after appearance and evolution with time of a premature degradation was carried out. A mechanism explaining the origin and the consequences of such degradation was suggested. Furthermore, studying the influence of the cathode thickness allowed distinguishing two of the main phenomena associated to H2O diffusion at the Ni-YSZ electrode. In addition, a study of the cell behavior after degradation by electronic conduction of the YSZ electrolyte showed formation of numerous porosities leading to delaminations at the YSZ/YDC interface. This phenomenon was characterized by a shift of the overall impedance diagram to the lowest frequencies, with appearance of a negative loop which finally leads to the disappearance of Rp as the current circulates mostly via electronic conduction of the YSZ electrolyte

Detailed Study of Degradation Behavior of Solid Oxide Cells in Electrolysis and Co-Electrolysis Mode

High temperature steam and co-electrolysis has a high potential for the efficient production of hydrogen or syngas. For a further development of this promising technology, development work on materials and cells as well as extensive operational experience is still needed. A main objective is to develop highly efficient and long-term stable cells and stacks using novel electrode materials and to improve the degradation behaviour by elucidating the relevant degradation mechanisms. Fuel electrode supported cells containing perovskite-type air electrodes were fabricated by ceramic processing and sintering techniques to be electrochemically characterized in electrolysis and co-electrolysis operating mode. I-V curves and electrochemical impedance spectra have been recorded for cell characterization. For a systematic investigation of the influence of relevant operating parameters such as temperature, current density and fuel gas humidification on long-term degradation a special test bench has been established which allows electrochemical characterization of 4 cells simultaneously under relevant SOEC conditions. This arrangement allows for variation of one distinct operating parameter while keeping other parameters strictly constant. A series of measurements over 1000 hours each in the temperature range 750-850 °C with different fuel gas humidity (40-80 mol%) and different current densities between 0 and 1.5 A/cm2 has been performed in steam electrolysis mode. Additionally, a second series of measurements has started in co-electrolysis mode at different operating temperatures and different steam-to-CO2 ratios. The progress of degradation was monitored in-operando approximately every 150 h by impedance spectroscopy. It was possible to differentiate different electrode processes, a mass transport limitation on the fuel electrode and the electrolyte resistance. Post-mortem investigations have been conducted to localize and identify the limiting processes and to clarify the correlation between degradation processes and operational parameters. In this paper the selection and preparation of electrode materials and the process of cell manufacturing as well as the experimental setup for cell characterization and long-term measurements are described. Results of electrochemical cell characterization performed at different operational conditions in electrolysis and co-electrolysis mode are shown and degradation phenomena observed and their underlying mechanisms based on different electrochemical processes are explained

Influence of Ni-YSZ Electrode Thickness on the Behaviour of Commercial Solid Oxide Electrolysis Cells by Mean of Electrochemical Impedance Spectroscopy

Electrochemical Impedance Spectroscopy (EIS) is used here in a two-electrode configuration to acquire a deeper comprehension of high-temperature solid oxide electrolysis cells (SOEC), distinguishing different phenomena related to electrochemical and degradation processes. Such approach is applicable to any kind of electrochemical cell. In the present study, chronopotentiometry and EIS are combined in order to analyze the influence of Ni-YSZ electrode thickness on the behavior of two commercial SOECs.</jats:p

Influence of Ni-YSZ Electrode Thickness on the Behaviour of Commercial Solid Oxide Electrolysis Cells by Mean of Electrochemical Impedance Spectroscopy

Our world is facing energy needs always growing, the mid-term disappearance of important energy resources such as fossil fuels and global warming issues consecutive to massive greenhouse gas production. A possible answer to produce renewable and clean energy consists in combining promising technologies such as solar photovoltaic, wind turbine and fuel cell, thus making an energy mix. Hydrogen is an energy carrier which can be part of this energy mix. High temperature electrolysis (HTE) using a solid oxide electrolyte is a clean way to produce, from water and electricity, hydrogen. However, many studies showed that the electrochemical phenomena related to the Ni-YSZ electrode have a strong influence on cell performances, including the ones associated to gas transport [1-3]. Further investigations on the hydrogen side of the cell are hence needed. In the following work, two commercial cells with different Ni-YSZ thicknesses are considered. A deep analysis is performed in a two-electrode configuration by mean of electrochemical impedance spectroscopy (EIS) with the use of electrical equivalent circuits (EEC), showing that all the main phenomena governing SOEC functioning are related to the Ni-YSZ electrode for both cells, each one characterized by a specific relaxation frequency and capacitance. Indeed, the impedance diagrams measured were deconvoluted, from the highest to the lowest frequencies, into four arcs: a high frequency arc (HF arc), a first middle frequency arc (MF1 arc), a second middle frequency arc (MF2 arc) and a low frequency arc (LF arc). These arcs were respectively associated to charge transfer at the Ni-YSZ electrode, a first H2O diffusion phenomenon, gas conversion at the Ni-YSZ electrode and a second H2O diffusion phenomenon. Thus, changing Ni-YSZ electrode thickness appears to mainly influence the H2O diffusion phenomenon associated to MF1 arc and the H2O gas conversion related to MF2 arc, while phenomena associated to HF and LF arcs are poorly sensitive to this thickness change. This result suggests that the phenomena associated to MF1 and MF2 arcs occur mainly in the volume of Ni-YSZ electrode, contrary to phenomena related to HF and LF arcs. This in the same time allows distinguishing the two H2O diffusion phenomena identified. [1] A. Nechache, M. Cassir, A. Ringuedé, J. Power Sources 258 164 (2014). [2] P. Kim-Lohsoontorn, J. Bae, J. Power Sources, 196, 7161(2011). [3] PK. Patro PK, T. Delahaye T, E. Bouyer E, PK Sinha, Int. J. Hydrogen Energy, 37, 3865 (2012).</jats:p

Detailed Study of Degradation Behaviour of Solid Oxide Cells in Electrolysis and Co-Electrolysis Mode

High temperature steam and co-electrolysis has a high potential for the efficient production of hydrogen or syngas. For a further development of this promising technology, development work on materials and cells as well as extensive operational experience is still needed. A main objective is to develop highly efficient and long-term stable cells and stacks using novel electrode materials and to improve the degradation behaviour by elucidating the relevant degradation mechanisms. Fuel electrode supported cells containing perovskite-type air electrodes were fabricated by ceramic processing and sintering techniques to be electrochemically characterized in electrolysis and co-electrolysis operating mode. I-V curves and electrochemical impedance spectra have been recorded for cell characterization. For a systematic investigation of the influence of relevant operating parameters such as temperature, current density and fuel gas humidification on long-term degradation a special test bench has been established which allows electrochemical characterization of 4 cells simultaneously under relevant SOEC conditions. This arrangement allows for variation of one distinct operating parameter while keeping other parameters strictly constant. A series of measurements over 1000 hours each in the temperature range 750-850 °C with different fuel gas humidity (40-80 mol%) and different current densities between 0 and 1.5 A/cm2 has been performed in steam electrolysis mode. Additionally, a second series of measurements has started in co-electrolysis mode at different operating temperatures and different steam-to-CO2 ratios. The progress of degradation was monitored in-operando approximately every 150 h by impedance spectroscopy. It was possible to differentiate different electrode processes, a mass transport limitation on the fuel electrode and the electrolyte resistance. Post-mortem investigations have been conducted to localize and identify the limiting processes and to clarify the correlation between degradation processes and operational parameters. In this paper the selection and preparation of electrode materials and the process of cell manufacturing as well as the experimental setup for cell characterization and long-term measurements are described. Results of electrochemical cell characterization performed at different operational conditions in electrolysis and co-electrolysis mode are shown and degradation phenomena observed and their underlying mechanisms based on different electrochemical processes are explained.  ACKNOWLEDGEMENT Financial support from the Helmholtz Association in the frame of the “Helmholtz Energy Alliance on electrochemical energy storage and conversion” is gratefully acknowledged.  References M. P. Hörlein, G. Schiller, F. Tietz, “Development and characterisation of sold oxide elec-trolyser cells, Proc. 11th European SOFC and SOE Forum, Lucerne, Switzerland, 1-4 July 2014, B1316 M. P. Hörlein, G. Schiller, F. Tietz, K.A. Friedrich, „Systematic Parameter Study on the Influence of Humidification and Current Density on SOEC Degradation”, ECS Trans-actions, 68 (1), 3553-3561 (2015) Y. Tanaka, M. Hörlein, G. Schiller, “Numerical Simulation of Steam Electrolysis with a Solid Oxide Cell for Proper Evaluation of Cell Performances”, International Journal of Hydrogen Energy, 41 752-763 (2016) </jats:p