Up to now, much work has been performed on the catalyst but much on the active layers’ structure and on the two other major components (carbon and electrolyte) whereas they do have a major impact on the MEA’s performance and on Pt utilization.
Based on this analysis, PEMICAN proposes to reduce the Pt loading for automotive application down to 0.15 gram of Pt per kW, by a twofold approach:
- to increase Pt utilization and power density by improving effective transport properties of ALs by tuning some properties of the electrolyte and by adding special carbon blacks in order to improve catalyst, electrolyte distribution and water management;
- to reduce Pt loading by controlling its distribution: very thin layer on the anode side and gradients of Pt on the cathode side. These structured layers will be defined in order to optimise the utilization of the Pt.
The combination of these two approaches will allow reducing the total mass of Pt for a given power density.
Whereas the main objective of PEMICAN is to develop and manufacture MEAs with reduced quantity of Pt, it is supported by numerical modelling to help defining the best Pt distribution. Special structural and electrochemical characterizations will be done to improve the existing models and to analyse the performance of our MEAs as a function of manufacturing processes and properties of components. Performance and durability tests under automotive conditions will be performed and analysed.
PEMICAN will demonstrate gains in terms of Pt cost (g Pt/kW) obtained by improving the design and properties of the ALs. Its results will be useful also In the future when non pure Pt is available.
The Consortium is built-up on the expertises of 6 European organisations with complementary skills: 2 Research Institutes (CEA and INASMET), 1 University (IMPERIAL COLLEGE), 2 industrial suppliers (SOLEXIS, TIMCAL) and 1 automotive OEM (OPEL). Among these partners, 4 of them are active members of the FCH JTI.
Final Report Summary - PEMICAN (PEM with Innovative low cost Core for Automotive applicatioN)
A Polymer Electrolyte Membrane Fuel Cell (PEMFC) is a device for generating electric current from hydrogen and oxygen via electrochemical reactions. It is made up of an anode, a cathode, and a polymer electrolyte membrane that separates these two electrodes. Anode and cathode consist of a gas channel supplying the reactant gases, a gas diffusion layer whose purpose is to transport the gases from the channels to the reactants sites, and an active layer (AL) where the electrochemical reactions take place. The combination of membrane and ALs is referred to as Membrane Electrode Assembly (MEA).
On the anode side, hydrogen molecules are split into protons and electrons. While the protons move through the membrane to the cathode the electrons cannot pass the PEM and must move to the cathode via an external current circuit, for instance feeding an electrical engine to power a car. On the cathode side protons and electrons react with the oxygen to form water. Under typical operating conditions this water appears in vapour form but also liquid water may occur, especially under heavy load. For automotive applications oxygen is typically taken from the surrounding air while hydrogen is supplied from an on-board storage system. Such a system allows producing electricity with no other exhaust gases than water (no pollution).
The active layers consist of carbon black, a polymer electrolyte also referred to as ionomer, Platinum (Pt) acting as catalyst metal, and some open pore space. Since Pt is extremely expensive it is desirable to reduce Pt loading, especially for automotive application for which cost is a major issue to allow its commercial development.
Up to now, a lot of work has been performed on the catalyst of the active layers of PEMFC but much less on the structure of the AL and on the two other major components (carbon and electrolyte) whereas they do have a major impact on the performance of PEMFC and on Pt utilization.
Based on this analysis, PEMICAN has proposed to reduce the Pt cost for automotive application by developing: a) MEA based on AquivionR ionomer with a total Pt loading decreased step by step from 1 down to 0.1 mg/cm²: b) specific tuned raw materials (AquivionR ionomer and Carbon Blacks) to improve performance and durability; c) low loaded MEA with alternative manufacturing processes (Physical Vapor Deposition, Direct Electro Deposition, Pt gradients) to check their performance.
These technological objectives are supported by a scientific approach: a) characterize properties of raw materials to link to performance and durability; b) develop innovative tools to measure major properties of active layers (proton conductivity, fundamental electrochemistry, gas diffusion…) to supply reliable inputs to modelling; c) develop Pore Network Model of the cathode to account for more realistic structure; d) improve performance models with better inputs and comparison to experiments; e) analyse limitation of performance as a function of Pt loading by combining fundamental characterization and modelling.
Even if the final target (0.15g/kW) has not been reached, PEMICAN has demonstrated the interest of AquivionR ionomer, the capability to influence performance and durability by tuning properties of raw materials, demonstrated the gain in terms of Pt cost from 1 to 0.3 g/kW, analysed the main limitations of performance as a function of Pt loading. These results can be useful also in the future when non pure Pt is available.
Dissemination has been done by presentation to conferences, publications, patents and intermediate results have been presented to an Industrial Boarding. A public website www.pemican.eu will remain live until spring 2017.
The Consortium is built-up on the expertise of 6 European organisations with complementary skills: 2 Research Institutes (CEA, TECNALIA), 1 University (IMPERIAL COLLEGE), 2 industrial suppliers (SOLVAY SPECIALTY POLYMERS; IMERYS GRAPHITE & CARBON, formerly TIMCAL) and 1 automotive OEM (ADAM OPEL AG).