Towards a better understanding of charge, mass and heat transports in new generation PEMFC MEA for automotive applications

Topic description

Specific Challenge:

Automotive application requests next generation PEMFC operating at high current densities (>2.7A/cm²), low noble catalyst loading (<0.08 mg/cm²), high power densities (>1.8W/cm², 9.3 kW/l), with high durability (>6,000h) and low cost (<50€/kW), as defined for horizon 2024 in the MAWP. The current status (for instance AutoStackCore project) is still far from these targets reaching approx. 1.13 W/cm², 4.1kW/l for approx. 0.4 mg/cm² during 3,500 hours. It is obvious that a disruptive approach is mandatory to reach these targets, including new materials and associated processes, new components design, and new stack architecture. Consequently, such next generation MEA (Membrane Electrode Assembly) shall deliver much higher power densities than the current ones and the SRU (Single Repeat Unit) of the stack will be much thinner and lighter, and based on ultra-thin MEA with ultra-low catalyst loadings. Based on this, two sets of questions can be highlighted i) what kind of new or exacerbated phenomena can occur with these next generation MEA, and ii) how can power density be increased when reducing catalyst loading at the same time? A common issue is to better understand the performance limitations for such MEA to propose new design and materials to overcome these issues.

Until now, the mechanisms inducing these limitations in performance are still under discussion and the relationship between the structure/design of the materials and the performance is not understood enough despite some recent progress. It is thus very difficult to define how far the performance could be increased by modifying the MEA. To better understand heat, mass and charge transport limitations in a MEA will allow proposing reliable breakthroughs in component design, operation strategies and performance prediction.

This topic is focused on the basic understanding of promising MEAs and MEAs components to meet the target of high-power density PEMFC single repeat unit. Only MEAs and MEA components showing performance greater than all of 0.79W/cm2 and 2,450hrs (which are approx. 70% of the current State of the Art (SoA) status quoted above) and at Platinum loading less than 0.50 mg/cm² (total loading) proven in automotive testing condition (as defined in JRC99115) are eligible as reference materials for this topic.

The project should include all of the following issues:

• Transport mechanisms, properties and limitations in the components (protons, electrons, liquid water, gases, heat) of the catalyst layer and microporous layer and at the interfaces, e.g. between catalyst layer and membrane, and between catalyst/layer and transport media in coupling with the electrochemical mechanisms. This includes the mechanisms and kinetics of the oxygen reduction reaction as a function of local conditions (temperature, partial pressure of reactants and products) in relation with catalyst surface structure and composition (e.g. oxides, hydroxides coverages). The Gas Diffusion Layer (GDL) and the interface between GDL and flow channels could be also considered if clearly justified as major issue. Project should be focused on MEA targeting ultra-low Pt loading (< 0.08 mg/cm²), high power density (> 1.8 W/cm²) and compact design (ultra-thin materials and designs, typically two to three-times thinner than today). The type of MEA should be proposed by the consortium while the project should account as much as possible for ‘generic’ situations applicable to SoA MEA and next generation MEA;
• The MEA should present reasonable durability, e.g. performance decay less than 50 μV/h. Durability is also an issue for such low catalyst loadings. As this topic is focused on understanding the performance limitations to increase power densities, the understanding of durability issues is not part of the topic. Nevertheless, it will be highly appreciated to check durability of the MEA tested and especially to test how durability is modified by using MEA with increased power densities due to better heat and mass transports inside the MEA;
• Combine experiments and modelling to predict the overall performance of a Single Repeat Unit (SRU) in a real stack geometry. It is expected to give the most accurate phenomenological description of the major limiting phenomena and their coupling thanks to specific experiments and the associated validated models. This should be assessed thanks to an accurate characterization, description and simulation of the local conditions and components structure and composition from 1-10 μm down to the 5-50 nm scale, considering the SRU design and real operating conditions. These measurements of the local conditions in a real stack design (MEA surface representative of a full-scale stack geometry) will also be established from the beginning of the project on the last state-of-the-art selected stack design and ultrathin MEA. The main idea is to bridge the gap between the local composition, structure and properties of the components, from the ‘micro’-scale, their effective properties at the ‘meso’-scale and their performance for different operating conditions when assembled in a SRU[1]. Mechanistic models for the description of the basic phenomena are highly desirable and then could be upscaled to be included in ones usable at the ‘macro-scale’. Model components and systems could be used for easier model validation in addition to dedicated validation experiments. The experiments must be conducted in conditions as close as possible to the ones of real operating PEMFC stack. Operando characterisation are recommended but ex-situ characterisation mimicking real conditions are also acceptable. At least, transport phenomena with phase change and two-phase flow must be addressed in the proposal.

The implementation of original methods or approaches is preferable, either in addition to or in coupling with improved conventional ones, both for experimental or modelling aspects.

In order to demonstrate the progress beyond the state-of-art in MEA development, the consortium should cooperate with the ongoing or finished projects (not only FCH 2 JU supported) in order to make consistent technical choices based on preliminary results from these former projects and target materials that have already proven certain performance.

The consortium is expected to contain at least one OEM partner that should take part in the technical work.

It is expected that the project will contribute towards the objectives and activities of the Hydrogen Innovation Challenge (as detailed under section 3.2.G. International cooperation). Promoting international collaboration beyond EU Member States and H2020 Associated Countries is therefore strongly encouraged.

TRL at start: 2 and TRL at end: 3-4.

Any safety-related event that may occur during execution of the project shall be reported to the European Commission's Joint Research Centre (JRC) dedicated mailbox JRC-PTT-H2SAFETY@ec.europa.eu, which manages the European hydrogen safety reference database, HIAD and the Hydrogen Event and Lessons LEarNed database, HELLEN.

Test activities should collaborate and use the protocols developed by the JRC Harmonisation Roadmap (see section 3.2.B "Collaboration with JRC – Rolling Plan 2019"), in order to benchmark performance of components and allow for comparison across different projects.

The FCH 2 JU considers that proposals requesting a contribution from the EU of EUR 2 million would allow this specific challenge to be addressed appropriately. Nonetheless, this does not preclude submission and selection of proposals requesting other amounts.

More than 1 project may be funded under this topic for complementary approaches.

Expected duration: 3-4 years.

[1]: Local properties and composition can include for instance 3D solid phase and composition at the pore scale (also called the ‘micro’-scale), effective properties refer to an average of the local properties over a heterogeneous system which can then be used to describe the system as a homogeneous one (also called the ‘meso’-scale), for instance effective electrical conductivity.

The project should result in:

• Justifying and characterizing the performance limitations and the effective properties of the MEA;
• Quantifying and predicting the local operating conditions inside a MEA;
• Designing recommendations for components to increase performance of MEA ;
• Preliminary orientations for future studies and development to reach the durability targets.

The main KPIs to be reached are the following:

• Power density > 1.8 W/cm2 at 0.66 V;
• Max operating temperature of 105 °C;
• Durability projected for 6,000 h;
• Pt efficiency up to 15 A/mg @0.66 V;
• Overall Pt loading < 0.08g/kW;
• Cell Volumetric power < 9.3 KW/l.

These KPIs should be reached under automotive operating conditions (as defined in the harmonised EU test procedure) and at single cell level: JRC99115.

Type of action: Research and Innovation.

The conditions related to this topic are provided in the chapter 3.3 and in the General Annexes to the Horizon 2020 Work Programme 2018– 2020 which apply mutatis mutandis.

International cooperation