Emission-free transport is a fundamental pillar for the energy transition towards a green energy landscape. Proton Exchange Membrane Fuel Cells (PEMFCs), using hydrogen (H2) and oxygen (O2), are at the forefront of the portfolio of practical solutions that are emerging on the market. However, Europe, and a fortiori France and Germany, has to develop a strategic positioning for research and development to maintain in-house the manufacturing of advanced and strategic technologies involved in the energy transition and thus preserve its independence; unlike as, e.g., batteries and solar panels production in spite of large investments. The present project proposal aims at identifying and unlocking obstacles limiting the implementation of promising O2 reduction reaction (ORR) catalyst materials, identified after fundamental and model investigations in well-controlled laboratory conditions, into efficient PEMFC cathodes. To this goal, a library of materials composed of state-of-the-art ORR nanocatalysts (octahedral, cubic, hollow, nanowires and spongy) will be built, and the synthesis processes will be scaled-up in a stepwise manner to reach volumetric quantities allowing MEAs manufacturing. The (i) structure and the chemistry of these nanocatalysts and (ii) the ionomer content and distribution within the cathode structure will be determined at each step of the membrane-electrodes assembly (MEA) manufacturing to rationalize changes of performance in model and real PEMFC systems. A specific diagnostic toolbox, combining advanced experimental techniques and modelling, will be specifically developed and the output of this toolbox will be used to adapt the ink formulation from which the MEAs are manufactured (catalyst content and chemistry, ionomer content and chemistry, solvent composition, use of additives). Strategies to mitigate issues related to low density of catalytic sites (highly-active ORR nanocatalysts usually feature large crystallite size), incomplete wetting of the catalyst by the ionomer and poor accessibility for O2 to the catalytic sites will be also developed. Finally, accelerated stress tests (ASTs) will be carried out. After characterisation, the results of these tests will help rationalizing why the degradation mechanisms may be different in simulated and real PEMFC operating conditions. Ultimately, the key findings of the project will be transferred to Heraeus and Symbio for industrial development. The ambitious research program proposed in the frame of the BRIDGE project requires efforts of scientific teams with broad interdisciplinary expertise in chemistry and physics, materials science and engineering. Therefore, this proposal brings together two groups at LEPMI/CNRS and ZSW, and two industrial partners Heraeus and Symbio. LEPMI/CNRS will use its expertise in the synthesis of ORR nanocatalysts and electrocatalysis using model electrodes to understand the structural, compositional and morphological changes occurring during elaboration of MEAs, while the ZSW group will engineer them to implement them in real-life PEMFC. The two industrial partners, Heraeus and Symbio, are a well-established catalyst materials manufacturer and an automotive equipment supplier designing and developing a large range of PEMFC related products, from specifically designed MEAs to a few hundreds kW systems, for electric vehicles, respectively. The BRIDGE project thus covers all the facets of a critical technology that is expected to grow further for the development of independent European-based solutions in the field of sustainable energy transition. It also intends to setup solid foundations for future original contributions from the French-German consortium in the field of PEMFCs electrodes technology/concepts, and its transfer towards the European industry.