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NOVEL Résumé de rapport

Project ID: 303484
Financé au titre de: FP7-JTI
Pays: Norway

Periodic Report Summary 2 - NOVEL (Novel materials and system designs for low cost, efficient and durable PEM electrolysers)

Project Context and Objectives:
The main objective of the NOVEL project is to develop and demonstrate an efficient and durable PEM water electrolyser utilising the new, beyond the state of the art materials developed within the project. The electrolyser will demonstrate a capability to produce hydrogen with an efficiency of at least 75% (LHV) at rated capacity with a stack cost below €2,500/Nm3h-1 and a target lifetime in excess of 40,000 hours (< 15 µVh-1 voltage increase at constant load).

To reach these objectives, NOVEL will develop and demonstrate enhanced components that are essential for cost-competitive, high-efficiency PEM electrolysis systems through five key concepts:
- Lower capital costs of the main stack components; membrane, electrodes and bipolar plates / current collectors
- Increase performance, in particular of the membrane electrode assembly (MEA), with reduced platinum group metals (PGM) loadings
- Longer life time of the most crucial PEM components, e.g. the membrane, catalysts and current collectors
- Novel system design for cost-efficient operation at high pressure and improved electrolyser lifetime.
- Development of accelerated stress test protocols for PEM electrolysers for lifetime evaluation and durability investigation of novel components.

The NOVEL project is a continuation of the NEXPEL project (, taking advantage of the successes in the project and continuing the development of the most promising technical solutions as well as capitalizing on the existing, well-functioning, organisational structure of NEXPEL.
Project Results:
During the second 18 months of the NOVEL project, the consortium has performed experiments on several protocols for accelerated stress tests for PEM electrolyser components and single cells and have selected a protocol for use in further stack testing during the final period of the project. The novel materials and coatings activity have evaluated several concepts and solutions for lower cost, higher performance components. The most promising concepts have been selected for up-scaling and will be demonstrated on stack level while others need further development and testing at single cell level. Among the new concepts developed are more active catalysts, membranes with higher performance and lower costs as well as non-noble coatings for bipolar plates and current collectors.
Durability/Lifetime evaluation of PEM electrolysers
This activity is dedicated to the development of AST protocols able to isolate and identify the degradation of the key component in a PEM electrolyser. The first project period was used to put in place an organization, different characterization tools and tests protocols in order to collect and analyse a large amount of information and measurements relating to the ageing mechanisms of PEM water electrolyser components (catalyst layers, membrane, current collectors and bipolar plates) and gain understanding of these processes. During the second period, modelling and experimental efforts brought interesting results. Among the most important achievements, a membrane degradation model that is able to capture the dependency between the fluoride release and the current, but also the effect of the temperature on the acceleration of the degradation has been developed. With such a model it was possible to propose an estimation of the membrane life with two scenarii in a first case, the coupling between membrane thinning and the acceleration of the oxygen crossover drag is not considered. In his case, the membrane shelf life is overestimated compared with the coupling model by a factor of 1.5 at 60°C and 1.6 at 80°C.

Subsequently, relevant AST on components level has been proposed to assess stability of materials such as catalyst or membrane. Accordingly, grafted membrane protocols were tested and α-methlystyrene with acetonitrile and 1,3 diisopropenylbenzene (AMS/AN/DiPB) was found to be most stable. Concerning the catalyst, novel Ir catalysts synthesized by Johnson Matthey was tested for the stability with a protocol that was developed by SINTEF. The new catalysts outperformed the stability of IrO2 and that catalyst might be suitable as an catalyst in an electrolyser MEA.

AST protocols on single cell level was developed by CEA and in combination with contact resistance measurements at Fraunohfer ISE, interesting results were found. In situ and ex situ characterizations led us to propose an AST protocol that could be tested on stack level. AST-2 which is based on step signal composed by 0.3 A/cm2 for 30 min and 3 A/cm2 for 15 min was able to thin the membrane with a rate of 50 nm/h after 285h of testing and a slope decay that could reach more than 1 mV/h at 2 A/cm2. Ex-situ contact resistance measurements showed us that the interface MEA // Porous sinters might be the most impacted interface during the AST and probably responsible of the performance fading during the AST.
Novel materials development
The objective of this activity is to develop new materials for electrocatalysts and novel membranes. Selection of type of membranes and catalysts for anode and cathode have been agreed upon by the consortium and NOVEL have continued to improve these materials and produce them in sufficient amount for production of MEAs for further testing in stacks. The materials selected at the milestone was further down selected to one cathode catalysts (Pt on C), two anode catalysts (iridium catalysts on support and a novel unsupported iridium oxide) and two type of membranes (radiation grafted membranes and modified PFSA membranes). Independently, all these materials showed promising performance
Focus has been on producing these materials by synthesis routes that is possible to scale up so enough materials can be delivered for MEA production which will be further used in different stacks developed and tested in the consortium. The materials have been delivered to JMFC for production of novel MEAs and initial test results have shown significant improvements over the baseline MEA. From this initial testing, a further down-selection of anode OER catalyst and membrane for stack development took place.
Even though Ir deposited on ATO and also on TiO2 based support materials show better activity related to mass of Ir compared to the a novel unsupported iridium oxides in ex situ tests, the performance of these supported electrocatalysts still show poor performance when used in MEAs. This is believed to be related to the poor intrinsic conductivity of the oxide support which only has a significant effect when a thick layer is combined with a porous current collector. Thus, the consortium have concluded to use the a novel unsupported iridium oxide, which also are believed to have lower costs compared to state of the art catalysts.
The membranes developed at PSI, based on the radiation grafting technology, offer the potential of significantly lowering the cost of the membrane. The ex-situ properties of the latest generation of membrane show a significant improvement in the figure of merit compared to Nafion membranes. The figure of merit combines crossover, resistance and mechanical properties for easy comparison of the different membranes. The PEM electrolyser performance of this type of membrane is comparable to that of Nafion® 117 but with a lower volume production cost. The second type of membrane is derived from reinforced, automotive relevant PFSA membranes and contains a hydrogen-oxygen recombination catalyst. These membranes offer improved performance and reduced gas crossover compared to the state-of-the-art Nafion® 117 membrane. The PFSA based route has been selected for stack MEA development due to the greater availability of large areas of this membrane whilst the radiation grafted membrane approach will be further optimised to improve the ex-situ performance and transfer those results to full PEMWE testing.
Development of low cost MEAs
The key objective of this activity is to create an MEA with better than state of the art performance at significantly reduced cost. In order to reach this objective, the new, lower-cost, components developed in the project will need to be combined successfully. It is also possible to reduce the cost of the MEA by improving the processes used to coat the catalyst layers on to the membrane.

A down-selection of new materials for the hydrogen (HER) and oxygen (OER) evolution reactions and the polymer electrolyte membrane has taken place and materials scaled to suitable levels for MEA development. The most significant improvement has been due to the incorporation of the new membrane developed. This is derived from reinforced, automotive-relevant PFSA membranes and contains a hydrogen-oxygen recombination catalyst. The addition of this catalyst allows the thickness controlled cross-over / resistance relationship for PFSA membranes to be broken in PEMWE operation. Thus, a thin (< 100 µm) membrane with low resistance and low crossover has now been successfully integrated with in-cell test results confirmed at a number of project partner labs.

A platinum on carbon HER cathode catalyst layer has been successfully incorporated into operating MEAs allowing a 50 % reduction in Pt loading with no loss of performance when compared to the baseline platinum black layer. The integration of the new OER anode catalysts has proven to be more challenging with the low conductivity of the supported Ir on ATO leading to poor initial MEA performance. Positive results have been obtained using a novel unsupported iridium oxide however, which has again allowed a 50% reduction in precious metal without significantly affecting performance. The new MEA has given > 100 and 150 mV performance benefit over the baseline at 1 and 2 A cm-2 respectively, operating at 60 °C, and these results are significantly closer to the target voltages, which are set at 80 °C. It seems likely that testing the new MEA at 80 °C will meet the targets.
Bipolar plates and current collectors
The objective of this activity is the improvement or replacement of the expensive titanium material and/or noble metal coatings used for porous current collectors and bipolar plates by coatings which suppress the formation of high contact resistances based on lower cost materials. Coating strategies were developed and candidate materials for bipolar plates and current collectors were selected. For this, a review of state of the art for thin film coatings on electrolysers, leading to an agreed prioritized list of candidate coatings for evaluation was given, and benefits and drawbacks for different coatings methods available were described, including possibilities for integration of coatings for catalytic recombination to increase gas purity. Coatings on bipolar plates have been tested with respect to their contact resistance and stability against corrosion in ex-situ setups. Physical and electrochemical methods of evaluation have been developed. The focus was on a fortified stress test, which allows comparing a set of coated bipolar plates with respect to their corrosion stability. Here, an accelerated stress test protocol has been developed for an ex situ testing of the corrosion stability of coated bipolar plates. It was applied on a set of coatings. Coatings have also been tested for their adhesion to the substrate material. A first generation of coated bipolar plates and porous current collectors have been produced on stack scale for integration in prototype stacks.
Stack design and system optimisation
The objective of this activity is to improve the electrolyser stack design (durability characterized in WP1) and system by implementing new components developed during the project (WP3 for MEA and WP4 for bipolar plates and current collectors).
An AREVA electrolyser stack producing up to 5 Nm3/h of hydrogen was assembled and tested in an outdoor existing system installed on AREVA Energy Storage site in Aix-en-Provence. The stack is based on the same design tested successfully by AREVA for more than 7500 hours in WP1 and will be used in WP5 to test new components developed during the project.
The system called the “Greenergy Box” is used for experimentations on hydrogen energy storage. The technical assessment of stack development in this WP was supported by economical evaluation. To meet required stack costs < 2,500 €/Nm³ H2, cost break down model permits definition of allowable component and manufacturing costs for the electrolysis (EL) stack. The cost break down model used in NOVEL was not newly developed but adapted from the previous NEXPEL project. It turns out, that the costs goals from the FCH JU can be meet with this stack concept for all three different cell sizes. Main finding are:
1. The relative cost share of the MEA depends only slightly from the cell size and has the highest or second highest share.
2. In this project costs for the MEA are dominated mainly by the production process and not by material costs for membrane and raw PGMs.
3. The larger the cell size the larger the cost share of the current collector made from Ti at the anode side. This effect is driven by the required increased thickness of the current collectors to ensure a proper flow regime in the half-cell.
4. From the economical point of view the costs associated with the current collectors at the cathode are minor.
Different options were investigated to reduce the overall investment costs for the stack. Most effective way to lower the investment costs is an increase in the current density at constant cell voltage. If this measure can be achieved more hydrogen is produced with the same amount of materials and in the same size of the stack. A reduction of the PGM loading for stacks with this cost structure is not the most effective way as the production costs for the MEA exceed by far the material costs for the catalysts and the membrane. A better approach would be the reduction of the costs associated with the production technology.

Potential Impact:
The results obtained in the second period of NOVEL are promising and demonstrate a high probability for achieving improved performance and reduced cost of PEM water electrolysers. The main expected outcomes from the technological developments are:

• A new generation of radiation grafted membranes for PEM electrolysers with significant reduction of the membrane cost.
• New oxygen evolution catalysts with significant improvement in catalytic activity for the oxygen evolution reaction and potential for noble metal thrifting.
• New non-noble coatings for Ti current collectors and bipolar plate with potential for reduction of the contact resistances in PEM electrolyser cells.
• Increased understanding of degradation issues in PEM electrolysers and parameters affecting overall lifetime which can contribute to increasing the lifetime of these units.
• Novel stack design, reducing construction material costs and easing assembly.

In addition, performed market analyses of the utilization of PEM electrolysers in different application areas (micro wind & PV for telecom, green H2 stations and large scale H2 production from renewable energy sources), will give a better understanding of the role of PEM electrolysers in a future hydrogen economy.

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