Periodic Reporting for period 1 - GAIA (next Generation AutomotIve membrane electrode Assemblies)
Reporting period: 2019-01-01 to 2020-06-30
WP2 deals with the requirements, test methods, operating conditions and performance benchmarking. The aim is to generate a unified approach to the evaluation of GAIA MEAs and MEA components for a state-of-the-art fuel cell system. Fuel cell system simulations showed that operating temperatures of > 100 °C are very favourable for system architecture and lower cost. Operating conditions for fuel cell stack operation, single cell operation and local operating conditions were set-up and hardware for both single cell and stack was defined.
Excellent progress has been made in WP3 culminating in an automotive size MEA comprising a thermostable nanofibre reinforced PFSA membrane that has withstood an exceptional 100,000 cycles (largely exceeding the Milestone 2 target) of combined open circuit voltage hold and relative humidity cycling at 90 °C, a result never hitherto reported. Novel formulations for nanofibre reinforcements reduce web fabrication time and lower the materials' costs. WP3 has developed a library of polymers with variation of the backbone structure, equivalent weight and molecular weight, with the aim of determining the impact of these variables on the oxygen permeation and MEA performance improvement once they are integrated into the cathode catalyst layer. A developmental coating line has been commissioned and validated for pilot level membrane production.
WP4 aims to design and develop high mass activity (MA), high stability nano-particulate or thin film catalysts supported on highly structured, surface-modified, corrosion resistant supports. Novel carbon supports have been prepared and sourced, and surface-modified by nitrogen plasma treatment to provide a range of modified carbons with the target corrosion resistance, surface area/porosity and tap density. Calorimetric and thermogravimetric methods have been developed to evaluate the strength of the ionomer-support interaction, and the interaction strength shown to increase with nitrogen modified carbons. Detailed physicochemical characterisation has been performed of the novel cathode layer ionomers prepared in WP3, including ionomer colloid particle charge and size in the solvents typically used in catalyst ink formulation. Novel catalytic entities have been prepared, comprising both thin films and structured particles, as platinum only and as alloys, in particular with nickel and with yttrium. Newly developed PtNi(Rh) ternary alloy nanoparticles achieve 0.6 A/mg Pt nd the target electrochemical surface area of 40 m2/g (Milestone 1). PtY alloy catalysts have provided the highest reported power density at high current density of any fuel cell with Pt-rare-earth catalyst at the cathode. Systematic study of the effect of catalyst particle location within carbon support micropores and outside of such micropores has provided direction for future work and, in association with a novel carbon support, have led to 1.5 W/cm2 at 0.6 V under project operation conditions, and 1.6 W/cm2 at 3 A/cm2 with cathode loading of 0.2 mg/cm2 at higher gas stoichiometry.
In WP5, testing capabilities were established for 10-cell short stack performance and degradation cycles, and for full-size single cell testing. MEAs were developed using new materials from WP3, 4 and 6. MEAs with novel ionomers designed to give increased oxygen permeability for the cathode catalyst layer were assessed to analyse the local transport resistances under a range of operating conditions. Catalyst materials from WP4 using a new carbon support lead to MEAs with lower mass transport resistance in particular at low stoichiometries. Work to assess catalyst layer additives has given increased tolerance of the additive containing catalyst layer to carbon corrosion ASTs. Alternative catalyst coated membrane manufacturing methods are providing improved performance under a wide range of conditions. A current mapping capability was commissioned that will show how different layer designs perform in different regions/operating conditions. MEAs were provided to WP6 for two short stacks. The first, using the benchmark CCM and the first iteration of improved GDL from WP6, provided 1.46 W/cm2 under the EU harmonised operating conditions (Milestone 3). The second stack iteration included a further GDL improvement, and new cathode catalyst layer technology using new materials from WP4 and optimisations to improve stability.
In WP6, the development of more graphitised gas diffusion and microporous layers has led to improved cell performance under GAIA operating condition. In testing of automotive size short stacks, the second generation of MEA gave more favourable cell voltages at all GAIA operating points, a specific operating point not reachable with the benchmark MEA was achieved with the second generation MEA, and >1W/cm2 was achieved at 105 °C. Durability tests of 600 hours with benchmark MEAs are currently running. With regard to MEA characterisation, novel hardware allowing for fast freezing of the water in the MEA was developed and validated, and methodology for sample-transfer and water imaging under cryogenic conditions by scanning electron microscopy was implemented. Preliminary end of test MEA analyses were initiated and will be fully applied on short stack MEAs having undergone durability tests.
In WP7, framed by an internal protocol on dissemination & knowledge management, GAIA has conducted activities to communicate on, and disseminate, project results, including through the implementation of a project website, use of visual identity tools, by conference presentations, a review article, project brochure, and annual newsletter, and a video clip conveying to a lay audience how to prepare and test catalysts and MEAs.
GAIA had the great honour of being part of the project cluster recognised in the FCH JU Awards 2019 as ""Best Success Story"" for ""driving forward automotive fuel cell technology""."