“…Hydrogen-related technologies represent a crucial field for moving to a low-carbon economy, which is expected to offer promising opportunities not only to fight climate change but also to enhance energy delocalization and safety, to revolutionize the transport sector both for goods and people and to develop local industries in many countries. , A clear evidence of this interest is proven by the enormous investments made in both Europe and in the United States for the development of hydrogen-based technologies, including fuel cells. − The high cost of these devices is due to the slow kinetics of the oxygen reduction reaction (ORR) at the cathode side, and so the use of Pt-based materials as catalysts is still required. − With their low cost, high availability, and good tolerance to poisoning, non-PGM is the best known alternative to Pt. , During past decades, various non-PGM catalysts were investigated: M–N–C based on porphyrin-like M–N x sites, non-precious metal oxide, chalcogenides, oxynitrides, and carbon oxynitrides . Among others, the most interesting and active are M–N–C with Fe metal center, where iron could coordinate from two up to five nitrogen functional groups, with the metal porphyrin-like Fe–N 4 site considered as the most important for the selectivity and activity in ORR. , A good catalyst is the result of a combination of several aspects like the site density, the intrinsic activity of sites, the carbon support hierarchical structure, the surface chemistry, the graphitization degree, and so forth. − Choosing the right carbon matrix is the turning point to improve catalytic performance. Indeed, increasing the density of the active sites is not sufficient to enhance the catalyst activity since it is also necessary to rationally design the textural and porous properties of the carbon support to facilitate the mass transport between micropores and the bulk solution. ,, Moreover, the catalytic enhancement can be obtained by the incorporation of heteroatoms like N, S, P, or B or another metal to form a bimetallic system. , …”