Periodic Reporting for period 2 - PEGASUS (PEMFC based on platinum Group metAl free StrUctured cathodeS)
Periodo di rendicontazione: 2019-08-01 al 2021-06-30
Proton exchange membrane fuel cell (PEMFC) is the predilection fuel-cell technology for automotive applications with a large deployment horizon by 2025-2030. However, the increasing use of fuel cell electric vehicles (FCEV) is expected to lead to a quickly growing demand for Platinum Group Metals (PGMs) because fuel-cell vehicles require a multiple of the PGM amounts needed for conventional cars, between 30 and 50 gPt for a 100 kW full power stack. PGM production is not only itself related to some negative environmental impacts (e.g. through the use of fossil-fuel energy for mining and metallurgical plants), but also raises questions of long-term availability due to the limitation of reserves and Europe’s economic dependence on the countries of the materials’ origin. I
Besides, durability and cost are also primary challenges to fuel cell commercialization. Fuel cell systems must compete with automotive internal combustion engines (ICEs) and other alternative technologies. The performance and durability of FCEV have already been proved for cars integrating high content of Pt based catalyst. To be also considered with incumbent and future competing technologies, the cost of automotive fuel cell systems needs to be competitive, both on the Total Cost of Ownership (TCO) and on initial cost basis (CAPEX). This cost must be achieved while ensuring that systems provide the performance and durability already demonstrated by high cost FCEV. One of the key issue lies on the fact that the cost of PEMFCs is driven by the use of Platinum (Pt), a very effective hydrogen oxidation and oxygen reduction catalyst, which represents an estimated 50% of the cost of the fuel cell stack.
Hence, it is of high strategic importance that the transition to a next-generation PEMFC using Platinum Group Metals-free (PGM-free) catalysts is made as quickly as possible to ensure Europe's competitive position and to reduce market pressure on the use of scarce noble metals. In that perspective, the PEGASUS project is exploring a promising route towards the removal of Pt and other critical raw materials (CRMs) from PEMFC and their replacement by non-critical elements.The overall aim of this project is to bring up the experimental proof of concept for novel catalysts materials & structures.
Besides, durability and cost are also primary challenges to fuel cell commercialization. Fuel cell systems must compete with automotive internal combustion engines (ICEs) and other alternative technologies. The performance and durability of FCEV have already been proved for cars integrating high content of Pt based catalyst. To be also considered with incumbent and future competing technologies, the cost of automotive fuel cell systems needs to be competitive, both on the Total Cost of Ownership (TCO) and on initial cost basis (CAPEX). This cost must be achieved while ensuring that systems provide the performance and durability already demonstrated by high cost FCEV. One of the key issue lies on the fact that the cost of PEMFCs is driven by the use of Platinum (Pt), a very effective hydrogen oxidation and oxygen reduction catalyst, which represents an estimated 50% of the cost of the fuel cell stack.
Hence, it is of high strategic importance that the transition to a next-generation PEMFC using Platinum Group Metals-free (PGM-free) catalysts is made as quickly as possible to ensure Europe's competitive position and to reduce market pressure on the use of scarce noble metals. In that perspective, the PEGASUS project is exploring a promising route towards the removal of Pt and other critical raw materials (CRMs) from PEMFC and their replacement by non-critical elements.The overall aim of this project is to bring up the experimental proof of concept for novel catalysts materials & structures.
The main goal of Pegasus was the synthesis of platinum group metal (PGM) free catalysts for oxygen reduction reaction. From the beginning of the project different PGM catalysts were synthesized with different morphology. Indeed, it is well known that the 3D structure of the catalyst support (for conventional platinum based catalyst) of the catalyst itself do have a direct impact on the performance the catalyst layer integrating them. So, PEGASUS developed different PGM free catalysts based on different carbon structures, different approach and synthesis routes.
First modification of graphene like matrix s by insertion of nitrogen and iron atoms via mechanical and thermal treatment allowed to produce a catalyst with a 2D structure. Second the modification of carbon nanotubes to integrate active site thanks to the used of Zinc Imidazole Framework (ZIF) as heteroatom carrier
allowed to obtain a complex structure similar to a mixture of graphene and carbon nanotubes. Then a unique 3D carbon structure integrating iron/nitrogen active sites and based on a sol-gel approach allows to obtain a catalyst using abundant raw material. Finally a mixture of the as prepared 3D carbon aerogel and modified carbon nanotubes allows to achieve a material with good ORR activity and improve mass transport properties.
The ORR activity was quantified and showed an increase by a factor 2 toward the unique available commercial PGM free catalyst used as reference in the project.
Then the catalysts were integrated in cathode active layer. Different printing processes were investigated, different ink formulation and active layer compositions were investigated.This allowed the consortium to produce membrane electrode assemblies (the core of PEMFC technology) by first producing catalyst coated membrane (CCM).
Then, the nature of the active sites, their quantification were performed using FT-EXAFS, CO and NO chemsisorption. The intrinsic activity of the developed PGM free catalyst were determined by scanning electrochemical microscopy (SECM) coupled with atomic force microscopy (AFM). The data gathered thanks to those technique coupled with the images of the MEA cross section and the performance in single cell, allow to have a model of the PMG free active layer.
The ORR activity of the PEGASUS catalysts were also compared to the PGM free catalysts received from the advisory board of the project, which allows us to situate the performance of the developed materiel toward the available SoA. .
A life cycle assessment, an up-scaling assessment and a technico-economical assessment of for the best catalyst from the project were made. The LCA study is public and available on the web site of the project. The technico economical assessment showed that, today a stack integrating the PGM free catalyst developed in Pegasus would not be cost competitive with a stack integrating platinum based catalyst. The threshold value for automotive stack integrating 2 mg/cm2 of PGM free catalyst at the cathode would be 780 mW/cm2 in system condition. This new target defines a new paradigm in the field of PGM free MEA and it appears that today the PGM free catalyst are not mature enough.
Finally, the results of the project were publicly presented during a dedicated workshop gathering the most recognized experts in the field of the PGM free catalysis for the PEMFC application.
First modification of graphene like matrix s by insertion of nitrogen and iron atoms via mechanical and thermal treatment allowed to produce a catalyst with a 2D structure. Second the modification of carbon nanotubes to integrate active site thanks to the used of Zinc Imidazole Framework (ZIF) as heteroatom carrier
allowed to obtain a complex structure similar to a mixture of graphene and carbon nanotubes. Then a unique 3D carbon structure integrating iron/nitrogen active sites and based on a sol-gel approach allows to obtain a catalyst using abundant raw material. Finally a mixture of the as prepared 3D carbon aerogel and modified carbon nanotubes allows to achieve a material with good ORR activity and improve mass transport properties.
The ORR activity was quantified and showed an increase by a factor 2 toward the unique available commercial PGM free catalyst used as reference in the project.
Then the catalysts were integrated in cathode active layer. Different printing processes were investigated, different ink formulation and active layer compositions were investigated.This allowed the consortium to produce membrane electrode assemblies (the core of PEMFC technology) by first producing catalyst coated membrane (CCM).
Then, the nature of the active sites, their quantification were performed using FT-EXAFS, CO and NO chemsisorption. The intrinsic activity of the developed PGM free catalyst were determined by scanning electrochemical microscopy (SECM) coupled with atomic force microscopy (AFM). The data gathered thanks to those technique coupled with the images of the MEA cross section and the performance in single cell, allow to have a model of the PMG free active layer.
The ORR activity of the PEGASUS catalysts were also compared to the PGM free catalysts received from the advisory board of the project, which allows us to situate the performance of the developed materiel toward the available SoA. .
A life cycle assessment, an up-scaling assessment and a technico-economical assessment of for the best catalyst from the project were made. The LCA study is public and available on the web site of the project. The technico economical assessment showed that, today a stack integrating the PGM free catalyst developed in Pegasus would not be cost competitive with a stack integrating platinum based catalyst. The threshold value for automotive stack integrating 2 mg/cm2 of PGM free catalyst at the cathode would be 780 mW/cm2 in system condition. This new target defines a new paradigm in the field of PGM free MEA and it appears that today the PGM free catalyst are not mature enough.
Finally, the results of the project were publicly presented during a dedicated workshop gathering the most recognized experts in the field of the PGM free catalysis for the PEMFC application.
The performance of the material developed in PEGASUS with the most recent SoA publicly available.
catalyst Activity:
catalyst activity obtained at 0.9 V (iR free) in 5 cm2 single cell under 1 bar H2/O2 and 100 %HR (total pressure 1.5 bar) at 80 °C:
PEGASUS: 18 mA/cm2 for 2mgcat/cm2 leading to a mass activity of 9 A/g cat.
SoA: 33 mA/cm2 for 6 mgcat/cm2 leading to a mass activity of 5.5 A/g cat (Jiao, L. et al, 2021, Nat. Mater.)
mass activity obtained at 0.8 V (iR free):
PEGASUS: 106 A/g
SoA: estimated to be 63 A/g (Jiao, L. et al, 2021, Nat. Mater. ).
Therefore it can be concluded that the more active catalyst developed in Pegasus is 1.6 time more active that the current SoA.
MEA performance:
the current density obtained in a 5 cm2 single cell at 0.6 V (no correction) under H2/Air (1 bar partial pressure), 100 %HR and 80°C:
PEGASUS: 420 mA/cm2 for the modified carbon nanotubes with 2 mgcat/cm2 .
SoA is 420 mA/cm2 for a PGM free catalyst loading at 4 mg cat/cm2 (Mengjie Chen et al, 2021, J. Electrochem.)
SoA is 410 mA/cm2 for a PGM free catalyst loading at 6 mg/cm2 (Jiao, L. et al, 2021, Nat. Mater.)
Therefore, it can be concluded that the MEA developed in PEGASUS and integrating Pegasus PGM free catalyst is one of the most active one comparing at 0.6 V with two times lower amount of material.
Today, and fairly speaking, the PMG free catalysts including Fe/N/C based active sites are not mature enough to compete with the last generations of platinum based catalysts for PEMFC, either in term of performance or final cost of the PEMFC stack.
catalyst Activity:
catalyst activity obtained at 0.9 V (iR free) in 5 cm2 single cell under 1 bar H2/O2 and 100 %HR (total pressure 1.5 bar) at 80 °C:
PEGASUS: 18 mA/cm2 for 2mgcat/cm2 leading to a mass activity of 9 A/g cat.
SoA: 33 mA/cm2 for 6 mgcat/cm2 leading to a mass activity of 5.5 A/g cat (Jiao, L. et al, 2021, Nat. Mater.)
mass activity obtained at 0.8 V (iR free):
PEGASUS: 106 A/g
SoA: estimated to be 63 A/g (Jiao, L. et al, 2021, Nat. Mater. ).
Therefore it can be concluded that the more active catalyst developed in Pegasus is 1.6 time more active that the current SoA.
MEA performance:
the current density obtained in a 5 cm2 single cell at 0.6 V (no correction) under H2/Air (1 bar partial pressure), 100 %HR and 80°C:
PEGASUS: 420 mA/cm2 for the modified carbon nanotubes with 2 mgcat/cm2 .
SoA is 420 mA/cm2 for a PGM free catalyst loading at 4 mg cat/cm2 (Mengjie Chen et al, 2021, J. Electrochem.)
SoA is 410 mA/cm2 for a PGM free catalyst loading at 6 mg/cm2 (Jiao, L. et al, 2021, Nat. Mater.)
Therefore, it can be concluded that the MEA developed in PEGASUS and integrating Pegasus PGM free catalyst is one of the most active one comparing at 0.6 V with two times lower amount of material.
Today, and fairly speaking, the PMG free catalysts including Fe/N/C based active sites are not mature enough to compete with the last generations of platinum based catalysts for PEMFC, either in term of performance or final cost of the PEMFC stack.