Further Understanding Related to Transport limitations at High current density towards future ElectRodes for Fuel Cells

Project Information

FURTHER-FC

Grant agreement ID: 875025

DOI

10.3030/875025

Project closed

EC signature date 5 December 2019

Start date 1 January 2020

End date 31 August 2024

Funded under

• SOCIETAL CHALLENGES - Smart, Green And Integrated Transport

Total cost

€ 2 735 031,25

EU contribution

€ 2 199 567,35

Coordinated by

COMMISSARIAT A L ENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES
France

Periodic Reporting for period 3 - FURTHER-FC (Further Understanding Related to Transport limitations at High current density towards future ElectRodes for Fuel Cells)

Reporting period: 2023-03-01 to 2024-08-31

Summary of the context and overall objectives of the project

The FURTHER-FC project proposes an innovative route towards a better understanding of performance limitations inside Proton Exchange Membrane Fuel Cells (PEMFC), focusing on the Cathode Catalyst Layer (CCL) as the major bottleneck for performance, cost and durability for future high performing low-Pt loaded PEMFC for automotive application.

Based on the active involvment of renowned actors, the project combines original and/or most advanced methods with intensive fundamental characterizations coupled with advanced models on CCL of various compositions/structures to conclude on transport and electrochemical issues.
The main objectives are:
• describe the CCL structure, transport properties and mechanisms at its different scales
• characterize local conditions in the CCL during operation
• establish the link between structure and properties of CCL, local conditions during operation, and performance
• propose and validate CCL with improved catalyst efficiency and durability

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Components and test stands
• specification and manufacturing of reference, customized (different Pt loading, I/C ratio, ionomer D2020 vs HOPI, carbon support, and ultralow loading MEAs (10 – 50 µg/cm²)
* analysis of performance limitations (O2 and H+ resistances, Limiting Current Analysis, Electrochemical Impedance Spectroscopy, electrochemical limitation, I-V curves…)
• specification and test of a final MEA with higher performance

Ex-situ characterization of Cathodic Catalyst Layers (CCL) and Gas Diffusion Layers (GDL)
• 3D image of GDL and MPL (X-ray, FIB-SEM)
• Structure of the CCL (FIB-SEM, HRTEM, e- tomography, SAXS, SANS, AFM): Pt nanoparticles size/distribution (internal/external to C), ionomer dispersion/coverage
• Effective properties of the CCL: electronic, protonic, and thermal conductivities, sorption isotherms, wettability
• Properties of thin ionomer films down to 6.5 nm: thickness, swelling, proton conductivity, oxygen transport resistance

Analysis of performance limitations
• Local water content and distribution in the MEA during operation
• Analysis of performance and resistance: polarisation curves, Limiting Current Analysis and Electrochemical Impedance Spectroscopy, ORR and HOR activities and orders of reaction
• Recommendations on the CCL structure

Modelling from nm to single cell scales
• Sub-µm scale: Lattice-Boltzmann Model (LBM) to simulate the local ORR rate and the coupled transports of oxygen and water in the gas and ionomer phase, analyze interfacial vs. bulk resistances, and influence of different ionomers and carbon supports
• GDL/MPL scale: based on the 3D images of real GDL, simulation of the heat conductivity and gas diffusion tensors by upscaling methods.
• CCL scale: based on the 3D images, simulation of effective oxygen diffusion and proton conductivity tensors, and ionomer and contact angle distribution
• Cell scale: improvement of the existing performance model by introducing the effective transport properties derived from the microstructure simulations of GDL/MPL and the local transport resistance distributions derived from the LBM

Dissemination and exploitation
• Two public workshops (06/07/2022, 11/12/2024)
• five Newsletters, several LinkedIn posts
• Participation to 21 conference
• Publication of 16 articles in scientific peer-reviewed journals
• Manufacturing of a 3D printed model of consolidated data from CEA and UES

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Characterization tools
• Improvement of electron tomography 3D image of the Pt spatial distribution on the carbon support (interior and exterior Pt nanoparticles)
• Progress on the quantification of the ionomer distribution (TEM, AFM, SANS)
• Combination of (AFM, FIB-SEM, HRTEM, 3D…) to analyse electrode structure at different scales
• H+ and O2 transport properties of down to 6.5 nm thick D2020 film as a function of temperature and Relative Humidity for different ionomers
• Effective properties of CCL (local and macroscopic scales), i.e. electric, proton conductivities, hydrophilicity
• Operando SANS to characterize water content in the MEA

Modelling tools
• Development of improved models and simulation tools for GDL/CCL/PEMFC
• Upscaling approach to model effective transport property tensors based on 3D images of GDL and MPL
• Such ‘scale bridging’ approach from the sub-µm scales to the cell scale, including Lattice-Boltzmann Model, Direct Numerical Simulation and macrohomogeneous performance model, opens the route to link the material properties to cell performance
• An in-depth model validation has been implemented

CCL structure and transport properties
• The ionomer reconstruction method in 3D digital images of CCL microstructure opens up new possibilities for characterizing the transport properties of CCL via numerical simulations
• The combined use of imagery techniques at various scales opens up also new prospects in terms of component characterization via numerical simulations
• The CCL effective proton conductivity tensor computed by direct numerical simulations from the FIB-SEM images after the ionomer reconstruction is in better agreement with experimental results than in previous works based on synthetic images
• The noticeable impact of proton transport in liquid water in the primary pores is confirmed by the numerical simulations
• The effective contact angle pore-scale distribution in the CCL microstructure is computed from the FIB-SEM images after ionomer reconstruction, and the CCL water retention curve computed is in line with experimental results

Limitation of performance
• Better understanding of the influence of ionomer (D2020, HOPI), carbon support (Graphitized, High Surface Area), and catalyst loading, for different operating conditions
• Different scenarii proposed to explain the performance limitations, some are fully validated by the different results of the project, others will need to be studied in more detail
• Suggestions of experiments for the future to even more understand limitations and propose catalyst layers with even higher performance and durability with even lower catalyst loading
• Improved CCL has been manufactured and tested with higher performance than the one at the beginning of the project
• Evidence of increased durability of MEAs using HOPI as ionomer in CCL for automotive application and of higher performance under heavy-duty relevant test conditions

Potential impacts
• TOYOTA MOTOR EUROPE is a leading actor in the Fuel Cell vehicles and FURTHER-FC has allowed access to a rich network of characterisation and modelling technologies, which improve our knowledge of the transport in the PEMFC. Some of these technologies will be used in the future in collaboration with partners to advance our research in Europe
• For the research institutes, FURTHER-FC has allowed increasing their knowledge in terms of material developments, deep analysis of experimental results and of performance limitation, developments of innovative experimental and modelling tools one of them has been patented and some of them allowed to have direct collaboration with European industrial partners to help them in their developments and raise their knowledge and knowhow…
• As an example, the methodology developed in FURTHER-FC, is now being used in another field (battery) in industry through the recruitment of a PhD student who developed it during the project.

3D TEM images of CCL and interior/external Pt onto C

AFM of CCL with different I/C ratio

Neutron imaging of liquid water during operation

3D PNM from a complete 3D image of MPL

Pt on HSAC, 3D FIB-SEM

structure reconstruction for Direct Numerical Simulation (CEA), based on 2D/3D images of the CCL

3D ionomer and transport properties

Height, deformation, adhesion, ionomer visible

Modeling transfers at different scales

3D image based modeling of transfers in a GDL with fibrous substrate, MPL and cracks

Proton conductivity of thin films of ionomer