Facts & Objectives

Facts

Since the first PEMFCs developed in the late 1950s there has been a remarkable technological progress towards increasing their efficiency and reducing the platinum loading, through the development of new membranes and electro-catalytic nanoparticles or the improvement of the electrode structure thanks to the growing fundamentals understanding in modern material and porous media science. On the other hand, the platinum loading reduction resulted on increasing the components structural complexity, especially of the Catalyst Layers (CLs): from this, even if the overall operating principle of a single cell remains relatively simple, complex mechanisms at different spatial scales strongly interplay during the PEMFC operation limiting the effectiveness of the catalyst activity. In fact, processes at the smaller scales, e.g. Oxygen Reduction Reaction (ORR) on the cathode platinum nanoparticles, dominate the processes at the larger scales (e.g. liquid water transport through the cathode carbon support secondary pores) which in turn affect the processes at the smaller ones, e.g. through the water flooding limiting O2 transport in the cathode. It is extremely important for automotive applications to accurately predict PEMFC state-of-health and remaining lifetime. For that purpose, it is necessary to develop diagnostic schemes that can evaluate PEMFC state-of-health adequately.

In order to achieve this, several steps are required:

  • to develop via physical modelling a better understanding of several individual processes in the cell components;
  • to understand the interplay between individual scales over the spatiotemporal hierarchies with their possible competitive or synergetic behaviour;
  • to identify the contribution of each mechanism into the global cell response under dynamic conditions;
  • to design separated controllers for an online control of the PEMFC behaviour to enhance its durability under specific operation conditions (e.g. by controlling the dynamics of the reactant relative humidity, the temperature, etc.).

Because of the structural complexity and multi-physics character of modern PEMFCs, interpretation of experimental observations and ultimate PEMFC optimization is a challenge. An analysis through a consistent multiscale physical modelling approach, in particular consisting on CFD models at the device level with high predictive capabilities towards the materials atomistic, chemical and structural properties, is required to elucidate the efficiency limitations and their location, the degradation and failure mechanisms. The development of such multiscale modelling approach and associated CFD models, must have several properties:

  • predictive capabilities of the relative contributions of the different scales and mechanisms into the macroscopic PEMFC efficiency and durability;
  • high flexibility towards its application to any type of chemical and structural properties of the used materials and components;
  • easily adaptable to any type of operation condition and system.

The PUMA MIND approach, consisting in building up a diagnostic and control-dedicated physical model with large prediction capabilities, enables:

  • reduction of the amount of experiments (and thus the cost) currently needed to build up classical empirical models with limited prediction capabilities;
  • a better targeting of experimental characterizations in representative conditions of the end user application;
  • new operation strategies reducing the performance degradation and also strategies to improve the stability of the materials and components;
  • the integration at EU level of modelling efforts usually developed separately. This will be done with the development of a modelling platform for more efficient communication and coordination for higher impact of the use of modelling on the PEMFC optimization in engineering practice.

All this will contribute on placing Europe at the forefront of fuel cell and hydrogen technologies worldwide and enabling the market breakthrough of fuel cell and hydrogen technologies, thereby allowing commercial market forces to drive the substantial potential public benefits.

Objectives

PUMA MIND is an ambitious project which aims to tackle, for the first time in the PEMFC community, the lack of understanding of the cell operation as a multiscale system, from the material to the system level.

The main goal of PUMA MIND is to establish a predictive modelling tool of PEMFC durability as function of their components composition and operation conditions representative or automotive applications. More precisely, this modelling tool will adhere to an integrative approach combining:

  • a detailed model of the electrochemical phenomena such as Hydrogen Oxidation Reaction (HOR), ORR, catalyst oxidation, dissolution and ripening, carbon support corrosion) in relation to the chemical and microstructural properties of the CL (catalyst size distribution, ionomer mesostructural properties, hydrophobicity of carbon support…);
  • a detailed model of the transport processes (charges, H2/O2, water), thermal management (GDL, MEA) and mechanical stresses (PEM) in relation to the microstructural properties of the CL, GDL and PEM;
  • a 1D cell level multi-scale model describing the competitive mechanisms (electrochemistry, transport, thermo-mechanical stresses) at multiple scales (from the material to the cell level) and allowing calculating their relative influence on the macroscopic performance and durability under current cycled conditions.

Calculation time with this model should be reasonable for engineering use, typically less of 30 minutes for simulation of 1000 hours of operation in appropriate computers;

    • a cell level multi-physics CFD model with 3D resolution of the processes involved during the PEMFC operation allowing to predict instantaneous efficiency as function of the materials atomistic, chemical and structural properties, and from that allowing to recommend operation conditions for improved PEMFC durability. The benefit of the integration of atomistic and mesoscale simulations data into the CFD model is clearly a significant enhancement of the performance and durability prediction capabilities of such type of codes, as several of the parameters currently used in and not accessible directly from experiments, are calculated in a consistent way from lower scale physical theories;
  • an innovative diagnostic and control oriented physical-model for online PEMFC diagnosis and real-time optimization of the operation conditions for enhanced durability. 

Calculation time with this model for engineering use should be sufficiently enough fast for appropriate integration in the system level. All model outputs will be validated with a systematic experimental methodology including materials and components chemical and microstructural characterization, ink, components and cell electrochemical testing.

The breakthrough outcomes expected from PUMA MIND are:

  • a set of simulation tools providing a better understanding of the interplay between mechanisms at different scales regarding the electrochemistry (including degradation such as catalyst dissolution, support corrosion, ionomer degradation), water management and thermo-mechanical stresses, and their relative impact on the whole cell behaviour in real automotive application conditions;
  • modelling strategies to scale up detailed physical descriptions of mechanisms into macroscopic models, and providing a better understanding of the relationships between the operation conditions (e.g. type of current cycle, relative humidity, temperature, pressures…), the components structural and chemical properties, and the long-term cell durability;
  • cell level models, in particular 3D CFD models, predicting durability as function of the materials chemical and structural properties, components and operation conditions;
  • on-line diagnostic model allowing to maintain the PEMFC operation under the appropriate conditions at a given current cycle for enhanced durability; o in strong connection with novel validation experiments in ex situ and in situ conditions, operation strategies to enhance the PEMFC durability with good efficiency.