D1.1. First Periodic consortium report

The project has run for 18 months allowing the first tasks to be fulfilled and to put the basis for the innovation and the improvements related to its activities. The main results achieved are related to the first Degradation Modes and Effect Analysis (DMEA) and improved awareness on the materials interaction and natural evolution under operation. The most critical issues and corresponding measurable parameters have been selected as a base for the definition of the Early Warning Output Signals (EWOS).

In the mid-term report the perspectives of the project, the issues to be solved and the deviations from the original DoW are defined. Most of the investigation protocols have been fixed and new typologies of samples more representative in respect to stack fractions were designed with the goal to support the modeling. Electrochemical, physical and mechanical models were refined or developed in order to have a precise description of the phenomena occurring in the stack aiming to reach the algorithms for use in predictive models.

D1.2. ENDURANCE project: Final report

The Project ended up after 38 months of activities reaching most of the initial goals. Two large stacks containing improved cells were operated in steam reformed methane as hydrogen source. The last one is still operating having passed over the 2.5 kh of activity. Several short stacks were built using improved sealants and improved cells. They are still under operation in pure hydrogen. A stack with segmented cell was shut down for post-operation analysis after 18 kh of work. New approach for analysis of the measured electrochemical data was introduced for increasing the sensitivity of monitoring deviations in the cell/stack operation behavior (Differential Resistance Analysis applied on VA curves) in order to be used for registration of EWOS and qualification of cells and stacks. Moreover predictive and descriptive models were improved reaching an excellent level of reliability. The materials and manufacturing improvements are therefore statistically validated.

D2.1. Endurance stack for Validation: Technical report

Two final stacks were built using the most advanced SOLIDpower design with improvements suggested by the results from the first half of the project. The progress in the cells design concerns the introduction of a more effective diffusion barrier between the electrolyte and the anode. On stack level a new glass-ceramic sealant selected over more than 10 formulations and the application of YSZ as a diffusion barrier between the stainless steel plate and the sealant were implemented. The performed testing confirmed the advantages of the upgrading on cell and stack level.

D3.1. Failure Modes and Effects Analysis- Part 1: Technical Report

Degradation Modes and Effect analysis have been carried out during the first stage of the project. The definition of signals from degradation at an early stage has been addressed at a first stage by using the experience of the previous experience involved partners. Databases from preceding projects and internal measurements at different sites has been put in common and analyzed as a basis for the execution of new experiments. For this task, an adapted ‘Degradation Mode and Effects Analysis’ (DMEA) method was used.

Huge bibliographic data was compiled, classified by critical phenomena studied and analyzed. A total about 150 papers made part of this study (attached as complementary information to this report). Simultaneously, a qualitative study was carried out of the data arisen from preceding projects. The information provided by this study was used, to take further decisions about the generation, distribution and characterization or testing of samples. The most likely affecting phenomena were determined and summarized: (i) Anode deactivation; (ii) Cathode/electrolyte interface; (iii) Oxidation of interconnectors in contact with the cathode and (iv) Sealing. A list with further experiments was defined and harmonized, using the capabilities of the different members of the consortium.

D4.1. Handbook of testing procedures and protocols

The “Handbook of Test Procedures and Protocols” is a collection of test procedures and protocols that were gathered, or developed and used within the ENDURANCE project. It is available for viewing and download here.

Currently in the field of PEM fuel cells for automotive applications an important JRC-led crosscutting activity ("Harmonization of Test Protocols") is running between several FCH JU projects. Recently similar initiative has been initiated for stationary applications where the protocols for PEMFCs are in more advanced stage. In the field of SOFC additional efforts are needed for accumulation of an information source as a base for the development of harmonized procedures. Accumulated previous experience is also needed for accelerating tests where non-reversible degradation caused by the selected performance conditions should be avoided. One of ENDURANCE’s objectives in respect to exploitation and dissemination was to accumulate existing information and to store developed project procedures for testing and characterization of SOFC.

During the project implementation data base “Handbook of Experiments (HoE)” was created in the Internal Website. It displayed a list of collected by the partners available experimental procedures/protocols sorted by upload date, uploader's name or institution, experiment and sample types. In addition to listing, the HoE gave the option to search protocols by the abovementioned parameters. The procedures and protocols developed in the frames of the project were also uploaded and shared between the partners.

At the end of the project, a selection of the accumulated information in the operating HoE was made and “Handbook of Test Procedures and Protocols” (for SOFC) was structured. It includes three main Chapters: (i) “Testing harmonized protocols” (4 protocols published by JRC); (ii) “Testing Procedures from the literature” (separated in two Sections: from Projects (14 materials) , and form Other Sources (11 Materials); (iii) ”ENDURANCE Procedures and Protocols”, which is structured in three Sections: Testing with 9 protocols, Characterization with 8 protocols and Technological Improvements with 2 protocols.

The “Handbook of Test Procedures and Protocols: is an open access project deliverable and can be downloaded from the project web site www.DURABLEPOWER.eu. There are also free of charge CDs which can be ordered from ENDURANCE coordinator (Paolo Piccardo This email address is being protected from spambots. You need JavaScript enabled to view it.).

D5.1. Protocols of analyses: Technical report

An important group of ENDURANCE experiments concerned characterization of micro-samples deriving from ageing and operating tests on cells and stacks. The data obtained by the partners using several techniques and tools are shared to evidence the ageing phenomena.

X-Ray diffraction experiments were performed on the top-surface of the samples (IREC). A preliminary evaluation of the secondary phases was done thanks to the Powder Diffraction File (PDF) database, while the diffraction data were fitted by the Rietveld method.

The samples were characterized by optical and electron microscopy (UNIGE). The methods of contrast used were the BSE (Backscattered electrons, sensitive to local compositional changes), and SE (Secondary Electrons, used when the topography of the image, e.g. porosity, was important). The analyses were performed by Energy Dispersive X-ray Spectroscopy (EDXS). SEM observations were also performed at: (i) coupled with quantitative and qualitative EDS chemical analyses (EPFL); (ii) coupled with EDX analyses (IREC). Secondary electron signals (SEs) were used for studying the topography of cells, backscattered electron (BSE) for element distribution, and In-Lens detector for studying the microstructure details at very high magnification and (iii) coupled with FIB, for quantitative 2-D and 3-D analyses at EPFL.

A special care was taken about the glass-sealant materials characterization (UNIGE). The goal was to study the evolution of both the bulk characteristics (crystallinity, porosity, precipitates, cracks) and those at the interfaces (layer formation, element diffusion, delamination). SEM-EDS analyses and SEM-BSE pictures were used.

Samples were characterized by TEM, HRTEM and STEM-EELS at IREC. TEM and HRTEM were employed to obtain information about the crystallographic structures. STEM-EELS were used to investigate variations in cation concentrations at the grain boundaries. The identification of the phases using the electron diffraction patterns / HRTEM images, and the inter-planar spacing were both performed by software programs.

X-ray nano-tomography experiments were carried out at CEA, to perform microstructural reconstructions of the aged cells and to get the main morphological properties of the complete electrode.

The cationic composition of the samples was determined by ICP-OES at EPFL, after complete dissolution in adequate liquid medium.

Raman imaging measurements were performed on the top-anode surface of aged cell by CNRS. The evolution of the cubic/tetragonal/monoclinic ratios of YSZ was analyzed more specially. Classical Raman measurements were also performed at IREC on cross sections.

The thermo-mechanical properties of the aged samples were measured at EPFL by 4-point bending (strength, elastic and creep properties) and dilatometry (thermal expansion).

Finally, SIMS experiments were carried out by CNRS on the cross-section of aged samples, to have an overview of the chemical diffusion processes.

D6.1. Modeling of stacks degradation and of failure probability

This deliverable presents the results from the series of thermo-electrochemical and mechanical models that were developed for improving the understanding and prediction of SOFC stack degradation. The model formulations were driven by experimental results (WP4 and WP5) with the goal of providing new capabilities for degradation modeling and capturing the regimes in degradation patterns as a function of operation history. The model scales span from the characteristic size of the material phases in the electrodes to those of the stack. The developed frameworks are integrated, i.e., continuum micro-models developed for phenomena analyses were implemented in full details up to the stack scale.

The focus in the thermo-electrochemical analyses was placed on selected phenomena: Ni coarsening, cathode destabilization/zirconate formation at interfaces, which were studied by time-lapse analyses and for some of them, by time-dependent simulations. EIS and degradation electrochemical simulations performed at the electrode and stack scale showed overall agreements with measurements, and supported establishing an improved understanding. Fine comparison however highlighted the difficulty to capture the complexity in full details (variability and exact local evolution).

Component irreversible deformation and geometrical imperfections were implemented in the stack thermo-mechanical simulations. A detrimental effect on the cell probability of failure was identified. The analysis of the distribution of the contact pressure at the cathode/GDL interface suggests that alterations of the electrical contact can contribute to the stack degradation and evolve significantly upon operation. However, for the simulated conditions and history, quantitative conclusions about the consequences for the quality of the electrical contact can at present not yet be provided, because of the complexity of the situation.

Summarized, current understanding leads to the belief that continuous stack performance degradation with long term operation stems from the incremental addition of cumulating processes, without these necessarily leading to end-of-life (on the contrary, rather flattening out with prolonged operating time), and that accidental, sudden, or eventual stack failure is likely rather due to thermomechanical issues, provoked either by cycling, or by progressive contact loss between the constituting layers.

D7.1. Technical Report: Failure Modes and Effects Analysis - Final version

Degradation Modes and Effect analysis has been carried out during the second stage of the project. The definition of signals from degradation at a second stage has been addressed by using the experience of the first stage of the present project, previous projects and internal measurements of the involved partners. Results from experiments of the first and second project stages at different sites have been put in common and analyzed. For this task, an adapted ‘Degradation Mode and Effects Analysis’ (DMEA) method was used. A summary of the effects with the highest impact in degradation is presented:

Anode deactivation is one of the main issues leading to decrease of the performance of fuel cells after long operating times. Several causes can lead to such phenomena: Ni coarsening, carbon deposition, anode poisoning etc. It can be remarked that the nickel phase mean diameter is increased after long-term operation. It has been found that the current density is not enhancing the nickel agglomeration. Time and temperature are strongly affecting the nickel phase evolution. The metal-ceramic interface does not change significantly with time whereas the surface in contact with the gas phase is strongly affected by the Ni coarsening. This statement indicates that Ni phase sintering in the cermet mainly results from the rearrangement of particles in contact with gas. The decrease of TPBs density is pronounced at 850°C whereas it is limited at lower temperature (750°C). Therefore, the decrease of the TPBs density appears to be clearly linked to the Ni coarsening upon operation. Temperature appears to be a major controlling parameter. The loss in active TPBs induces a deterioration of the cell performances. The contribution of nickel agglomeration can be estimated from the loss of performance obtained with the modelling approach. The nickel agglomeration is explaining a part of the measured degradation. After 1000 h, the cell voltage is decreasing of 1.1 mV according to the simulation. This value corresponds to about 32% of the total degradation rate obtained with the experiment.

LSCF demixing has been investigated in the second part of the present work. For this purpose, the phase reactivity with the electrolyte and more particularly the formation of ZrSrO₃ has been characterized before and after the durability experiments. Formation upon operation of a secondary Sr-rich phase (which corresponds to the SrZrO₃ crystalline structure identified by X-ray μdiffraction) was noticed. This secondary phase is found to precipitate in the open porosity of the barrier layer at the interface with the electrolyte. However, the amount of this secondary phase is very restricted. As a conclusion for Endurance Project, it is claimed that, in our conditions, LSCF destabilization does not significantly participate to the degradation of cell performances during fuel cell operation. Deactivation of cathode due to the presence of contaminants like chromium, mainly coming from interconnect steel, is probably one of the main cathode poisoning agent. The chromium deposition and poisoning is a complex process, due to many interrelated factors. Several measures have minimized the chromium poisoning, which has substantially reduced the importance of these phenomena for the current project compared with previous ones. A more important accent is put in the role of eventual SiO₂ contaminants coming from the seal.

The cathode/electrolyte interface plays a significant role on the overall SOFC performance and therefore, it has attracted ongoing research efforts. The interaction between iron-based perovskite cathodes and YSZ electrolyte forms poorly conducting secondary phases, such as SrZrO₃, which degrade the cell performance. The influence of both the thickness and microstructure of the CGO interlayer has been also considered. In the CGO screen-printed interlayers, the formation of SrZrO₃ occurs during the cell fabrication, mainly depending on the method deposition of interlayer and the sintering temperatures of CGO barrier layer and cathode. In operation at long-term, no variation of the SrZrO₃ amount was observed. Insight on the phenomena involved in the Sr, Y, Ce and Gd diffusion has been very valuable for the fabrication of better performing future generations of cells. Since the secondary phases (SrZrO₃) of CGO barrier fabricated by conventional techniques (screen-printing), which require high sintering temperatures (>1200ºC) and present high porosities, a counter strategy consisted in the analysis of dense CGO barrier layers at low temperature. For this purpose, the PLD technique has been employed to prepare dense barrier layers. Voids and delamination between electrolyte and barrier layer have been formed in the cells without annealing in the dense barrier layer, due to the cation diffusion that occurred during cell testing. In the PLD CGO interlayers optimally annealed after deposition and before cathode sintering, only the cells operated at high current densities presented nano-porosity at the interlayer/electrolyte interface.

The oxidation of interconnectors in contact with the cathode leads to an important growth of the resistivity of the cell. In order to prevent this effect, protective layers are applied that act also as barrier for chromium diffusion. The samples exhibited a thin chromia scale at the alloy/coating interface plus spinel phases as a reaction layer between the chromia and the manganese cobaltite coating. The oxidized samples also exhibited MnCr₂O₄ spinel at the chromia/alloy interface. The formed layers showed changes in thickness, morphology and composition, attributed to changes in sample preparation and degradation experiment. The current state of the art samples from Endurance use a special stainless steel (SSK41X) coated with a Mn-Co protective layer. The effectiveness of this layer as Cr barrier has been matter of attention.

D8.1. Workshop Proceedings

In the spirit of the FCH JU’s goal to increase the networking between projects working is similar areas, the ENDURANCE team was the initiator of the Workshop “Degradation Mechanisms in Solid Oxide Cells and Systems" which was co-organized together with four FCH JU projects - DIAMOND, SOPHIA, SOCTESQA and Eco - and held in Barcelona, Spain (February 17, 2017). It gathered high-level researchers and industrial representatives involved in the development and market introduction of solid oxide cell systems. Download the Workshop Proceedings from here.

The aim of the workshop was to provide a platform for professional discussions and exchange of expertise in one of the most challenging issues in the commercialization of SOFC: degradation and durability. Different aspects covering cell components, seals and interconnectors, as well as stacks and systems were discussed. Diverse approaches were presented: from modeling and prediction of degradation, through experimental confirmation and observations to diagnostic tools for early detection and mitigation strategies.

The Workshop Proceedings include abstracts and full presentation of the talks, divided in six thematic sections. They are available in an open access final version of ENDURANCE web site, as well as CDs for dissemination during participation of ENDURANCE members on different scientific events.

D8.2. & D8.3. Interactive Software Toolkit (Serious Game) with clip

Only once the general population is aware of the opportunities offered by the usage of renewable power sources related to hydrogen can an open market for such products come into existence. For this to happen, the awareness of the system safety must be popularized and accepted into mainstream thinking, then the advantages can be disclosed and the perspectives anticipated. 

The dissemination towards the public has more general goal – to increase the public awareness of the fuel cells and hydrogen importance for sustainable and secure energy via the project achievements. Young people - pupils, students are an important targeted group. In this direction a special deliverable product has been planned with longer term impact – a clip and a video game. After the start of the project they were united in a more sophisticated product – the so called Serious Game, named “The Lost Colony”. The main target audience of "The Lost Colony" software kit constitutes teenage high school students, since they are the customers and developers of the future. They will be the first living the Hydrogen Age and shall feel their involvement to build it.

The goal of the Serious Game is to transfer knowledge related to fuel cells. Following the spiript of the game, the players jump in the year 2115 when the Earth’s energy sources are nearly depleted; therefore, humans have decided to colonize Mars where energy is produced using fuel cells - devices that use Hydrogen and Oxygen. To explore the Martian colony the gamers have to complete a series of didactic mini-games present in the 3D environment. At the end they should have learned the basics on how fuel cells and electrolyzers work and can be used.

For the moment the game is written in English and translated in Italian, Spanish French, Dutch and Bulgarian. It can be played online or downloaded from here. CDs are recorded for further dissemination.

Higher levels of the Serious Game can be further developed where the players can design original application solutions. Competitions can be organized in different EU countries and regions, starting with the FCH JU members. “The Lost Colony” can be further developed in FCH JU cross-cutting activity and transformed in attractive dissemination tool with long term impact.

D8.4. Web site

The ENDURANCE project website www.DURABLEPOWER.eu constituted an integral tool in the project's online communication strategy. The responsive website was designed to feature an engaging external section and a restricted access internal section – a virtual “hub” for project information and pooling of partner resources. The consortium work was facilitated by convenient Databases as : (i) Book of Samples which cataloged each project sample, all testing results, thus allowing ENDURANCE team members to view in every moment the status of all samples; (ii) Handbook of Experiments (HoE), where testing procedures and protocols that have already been implemented, or developed during the project implementation, where collected and stored.

Once the project entered into its more definitive stages, in addition to project objectives, challenges, progress, and achievements, the external site featured background articles and interactive and educational content regarding ENDURANCE in the context of improvement of fuel cell performance through early warning signals, fuel cells as an up-and-coming technology, as well as a broader view of the potential and reality of the Hydrogen Economy. Separate information sections were directed towards the main project target groups - scientific, industrial and public.

In every project the strongest and valuable achievements are realized in its last stages. For increasing the impact of the project achievements, a Final version of ENDURANCE web site was designed, which will continue to operate at least 3 years after the termination of the project, i.e. till 2021. The most valuable information about the project and its activities and results is included. Three of the final deliverables: (i) Handbook of Testing Procedures and Protocols” – a collection of test procedures and protocols; (ii) Proceedings of the Workshop “Degradation Mechanisms in Solid Oxide Cells and Systems"; and (iii) the Serious Game “The Lost Colony” (written in English and translated in Italian, Spanish French, Dutch and Bulgarian) which supports the dissemination of knowledge about fuel cells in an original and attractive manner, are available with free access.