- D4.2 - Effect of addition of ROS on durability improvement - CONFIDENTIAL
A reference Fe-N-C catalyst, containing Fe mostly in the form of atomically-dispersed FeNx active sites for oxygen reduction reaction, was modified by addition of targeted solid-state catalytic ROS scavengers. The benefit toward improving the durability of the reference Fe-N-C material was assessed, first via ex situ peroxide degradation protocol (see D4.1). The results identify lower peroxide production and improved durability with a selected FeNC/additive composite. Future work will focus on more advanced functionalisation of FeNC to improve the additive dispersion and binding to FeNC, as well as verifying improved durability in fuel cell testing of such PGM-free composites.

- D.4.3 - Report on sacrificial organic compounds as ROS scavengers to actively protect Me-N-C catalysts against H₂O₂ - CONFIDENTIAL
A model Fe-N-C catalyst, containing Fe exclusively in the form of atomically-dispersed FeNx active sites for oxygen reduction reaction, was subjected to the ex situ peroxide degradation protocol (see Deliverable D4.1), in absence and then in presence of three different organic radical scavengers, which were selected for their reported antioxidant properties in the field of chemistry and biochemistry. The benefit toward improved stability of the reference Fe-N-C material after exposure to large amount of H₂O₂ was assessed by comparing the ORR activity of the Fe-N-C catalyst before and after the ex situ accelerated stress test (AST) peroxide protocol. Initial promising results were obtained with one of the organic radical scavengers. Its addition during the peroxide accelerated stress test resulted in reduced Fenton reactions on the model FeNC catalyst, as deduced from lower %H₂O₂ during ORR after the AST, when compared to the same FeNC catalyst in absence of the organic radical scavenger during the AST.

- D.4.4 - Durability of platinum-free cathode layers in single cell PEMFC - CONFIDENTIAL
The stabilisation of PGM-free catalysts (Fe-N-C and other metal-N-C) was investigated via the addition of solid-state scavengers for peroxide or reactive oxygen species in the cathode layer, or onto the M-N-C catalysts. ZrO₂, zinc-molybdates and MnOx materials were investigated as stabilisers, as well as ultralow amount of Pt. The stabilisation effects induced by the co-catalysts were studied in rotating (ring) disk electrode set-up, ex situ with catalase and peroxidase tests, and in a PEMFC.

- D5.1 - Identification of the main performance loss mechanisms seen in layers made from reference catalyst - CONFIDENTIAL
This deliverable report presents results obtained with the Reference hybrid 2% Pt/Fe-N-C catalyst. Layers were created with this catalyst and assembled into membrane electrode assemblies with an active area of 50 cm². State-of-the-art membranes were used with good conductivity and a thickness of 15 mm. Pt/C was
used as an anode catalyst at a loading of 0.20 mg Pt/cm². The Reference catalyst layer exhibited low performance, compared to state-of-the-art Pt/C cathode catalyst layers, and is currently 400 mV below the ultimate project target at 600 mA/cm².
This report contains characterisation studies of the catalyst and a series of diagnostic experiments carried out in 50 cm² fuel cells to gain better understanding of the limitations of the layers made with the Reference catalyst.

- D5.2 - Quantification of the performance improvement achieved by rational re-design of layers using the Reference catalyst - CONFIDENTIAL
This deliverable report presents a detailed optimisation of the cathode catalyst layer that has led to the highest performance in the project so far. This was achieved in 50 cm2 single cells using a second, scaled-up batch of the project Reference hybrid 2%Pt/Fe-N-C catalyst. It was observed that small changes in synthesis led to significant physical differences between the first and second batches of the project Reference catalyst. This was a significant learning exercise that highlights the difficulties in scaling up this type of catalyst. This report gives an in-depth characterisation of the properties of the catalyst and catalyst layers made from the project Reference catalyst, building on methods described in D5.1. It was deduced that a lack of porosity below 100 nm led to low performance at medium to high current densities. It was possible to improve performance, however, with the use of different solvent contents during the inkmaking step and with the addition of different additives. This approach was able to increase the porosity in the catalyst layer at

- D.5.3 - Most promising catalysts from WP3 and WP4 scaled up and shown to match performance of small batch samples - CONFIDENTIAL
This deliverable report presents the different catalyst variants developed in WP3 and WP4 and the selection criteria that identified the candidates for scale up in Task 5.3. From WP3, three FeNC type catalysts were identified and from WP4 three radical scavengers were also identified. In collaboration with the project partners, candidates for scale up at JMFC were selected based on activity, durability and ease of scalability. The team agreed to progress the CNRS (FeNC) cathode catalyst from WP3 with 1 wt% Pt added as a radical scavenger (from WP4). Precursors were sourced at JMFC for the synthesis of a 60-100 g batch size of the FeNC catalyst. JMFC and CNRS started a close collaboration to transfer the synthesis method. Some modifications were made to the CNRS method, mainly for compatibility with the equipment available at JMFC. The first iteration was successful and a 35 g batch was produced. The first batch of scaled-up catalyst was sent back to CNRS for characterisation and validation in the RDE and in MEA. After review of the results with CNRS, the scaled-up catalyst was qualified to progress towards MEA fabrication for activities planned in WP2 and, therefore, met project Milestone 6, ‘Go/no-go decision on catalyst scale-up for industrial-scale single cell with option for short stack’.

- D.5.4 - 50 cm² active area CCMs fabricated using the most promising catalyst for testing in BMW hardware in WP2 - CONFIDENTIAL
This deliverable reports the optimisation of cathode catalyst layers using the CRESCENDO scaled up catalyst. A set of four different cathode designs were produced using two different coating methods. A series of experimental parameters such as loading, use of an additive and coating method were varied. The additive was aimed at increasing the catalyst layer porosity in the smaller pore region, i.e. <30 nm. The use of spray deposition allowed the creation of higher loading layers, circa 3 mg catalyst/cm², with acceptable layer quality with respect to crack formation. On the other hand, the use of K-bar coating was better suited for lower loadings, i.e. 1 mg catalyst/cm². The scaled-up catalyst outperformed the project reference catalyst in the kinetic (low current) region under H₂/air. Using layer type 1 however, high mass transport losses were seen, thought to be due to low layer porosity. With layer type 2, the scaled-up catalyst clearly outperformed the reference catalyst, at the same loading and with the same layer configuration and was able to reach high current densities up to 1200 mA/cm². This good result demonstrates the higher activity of the scaled-up catalyst in an appropriate layer configuration. Out of this work, a set of five different cathode designs were produced and sent to BMW as part of WP2.

- D6.2 – Ultra-low PGM anode catalyst with improved resistance to CO poisoning - CONFIDENTIAL
This report describes the development of a novel ultra-low PGM anode catalyst with outstanding tolerance to carbon monoxide (CO) poisoning. When this newly developed catalyst was applied in the anode of a PEMFC, no performance degradation was observed even when cell was operated with hydrogen fuel containing 5000 ppm CO. The performance of this catalyst is closely matching the project targets and will be further optimised to enhance its absolute HOR activity. In parallel, floating electrode studies were carried out using Pt and PtRu catalysts to investigate the CO poisoning behaviour at ultra-low loadings and CO adsorption was modelled using Langmuir-Hill isotherm. It was found that at ultra-low loadings, both Pt and PtRu catalysts lose their activity significantly in the presence of CO. Model fitting revealed that 50% CO surface coverage of Pt is reached with a CO concentration of 14.7 ppm which is less than half of 35.4 ppm needed for PtRu. At a high CO concentration of 200 ppm, more than 90% Pt sites and over 80% PtRu sites are blocked resulting in almost their complete deactivation for hydrogen oxidation reaction (HOR).

- D6.3 – Report on activity, resistance to poisoning and stability under cell reversal conditions of down selected non-PGM and ultra-low PGM anode catalyst - CONFIDENTIAL
This report describes the characterisation of the down selected non-PGM and ultra-low PGM anode catalyst for the Hydrogen Oxidation Reaction (HOR) developed in the first part of the CRESCENDO project. The first part of the report describes the performances for hydrogen oxidation obtained with the Ni based bio-inspired catalyst at CNT modified electrode in aqueous acidic electrolyte (half-cell and floating electrode configuration) as well as in MEA configuration (hydrogen pump). The second part focuses on the characterisation of the ultra-low loading anode, tested in floating electrode configuration and directly in an H₂-O₂ fuel cell setup.