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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - CRESCENDO (Critical Raw material ElectrocatalystS replacement ENabling Designed pOst-2020 PEMFC)

Teaser

Summary

CRESCENDO aims to develop highly active, stable and durable electrocatalysts using non-platinum group metals (non-PGM) for the PEMFC cathode and includes the re-design of the cathode catalyst layer, with a project target power density of 0.42 W/cm2 at 0.7 V in single cells. CRESCENDO also has the objective to develop non-PGM or ultra-low PGM anode catalysts with greater tolerance to CO and H2S than current low loading Pt anodes. The development of innovative PEMFC materials having significantly lower platinum contents will avoid dependency on the supply of critical raw materials, consolidate Europe\'s competitive position, and reduce market pressure on the use of scarce noble metals. Provided that the non-PGM based MEAs are able to provide the high power density at high current density required by FCEVs, the resulting cost savings will be game-changing.

Work performed

The very ambitious fuel cell power density and durability targets of CRESCENDO are far beyond the state of the art. The project team is tackling, head-on, the crucial bottlenecks in non-PGM fuel cell catalysis by developing new methodologies for the determination of catalyst descriptors hitherto not considered, in parallel to new catalyst development, new approaches to catalyst stabilisation and cathode catalyst layer re-design specific to non-PGM catalysts.
In Work Package (WP) 2 on Requirements, Benchmarking, Industrial scale testing, Life cycle and Cost analyses and Exploitation Potential, fuel cell operating conditions and testing protocols were defined based on the automotive system requirements (BMW). The partners benchmarked commercial CCMs and catalysts to provide a reference for the project.
WP3 is dedicated to the development of non-PGM cathode catalysts. Following complementary synthesis strategies at partners TUB, CNRS, ICL and UNIPD, the new catalysts were evaluated using rotating ring disc and floating electrode techniques. Currently the highest activity observed (0.92 A/g at 0.90 V RHE) is considered to reach the mid-term target of 1 A/g at 0.90 V RHE. In initial fuel cell tests on hydrogen-oxygen, a current density of 15 mA/cm2 at 0.9 V was achieved, a considerable improvement from the project start point, and good progress towards the mid-term target of 25 mA/cm2. In a hydrogen-air fuel cell, where the project final target is to reach 0.7 V at 600 mA/cm2, the project status at this current density is 0.47 V. Although all materials have iron-nitrogen moieties as the catalytically active species, different limiting factors were identified for each catalyst type, and this learning will be use to guide the development pathways in the second period.
In WP4 on Diagnostics and Approaches for Improved Non-PGM Cathode Durability, the consortium optimised existing methods and established novel diagnostic tools for accelerated durability testing and for measuring the site density and turnover frequency in ex situ, post mortem and/or operando conditions. Sacrificial and regenerative scavengers for reactive oxygen species were investigated to improve the durability of an Fe-NC Reference catalyst. Using the second of these approaches provided probably the first demonstration of the rational stabilisation of PGM-free M-NC catalyst by a PGM-free co-catalyst, and potentially opens up a rich landscape of PGM-free co-catalysts with improved stability during PEMFC operation. Efforts will be focused in the next reporting period on optimisation of the co-catalyst/catalyst synthesis, since this is essential to achieve the final project durability target. Model surface studies shed new light on the stabilisation of Fe-NC catalysts by ultra-low amounts of platinum. Of fundamental importance for this particular catalyst design, it also represents a potentially new approach for novel catalytic systems for ORR in an acidic medium.
WP5 has produced valuable knowledge of the challenges to be overcome in both scaling-up an Fe-NC catalyst and in designing a successful catalyst layer from such a catalyst. This type of work is rarely reported in the public domain and it is expected that CRESCENDO will make a significant contribution to this field. Different synthesis approaches were explored at JMFC to scale-up a previously developed catalyst (Reference catalyst), which resulted in the successful synthesis of two batches at scales of 10 g and 20 g. Testing in 50 cm2 single fuel cells showed that the performance of the Reference catalyst on air was, initially, 500 mV lower than the ultimate project target of 0.7 V at 0.6 A/cm2. In-cell diagnostics were complemented by ex situ characterisation, which showed that the Reference catalyst formed layers with low pore volume and pronounced hydrophilicity, compared to a conventional Pt/C layer. By optimisation of the ink and catalyst layer properties, significant improvements to the layer performanc