The Fe-N-C electrocatalysts have emerged as a promising alternative to the Pt-based electrocatalysts currently used for the oxygen reduction reaction (ORR) at the cathode of proton exchange membrane fuel cells (PEMFCs) [1]. Although great progress has been made, there are still many challenges to solve to promote the use of this technology at an industrial level, such as the stablish a profitable and scalable method to synthesize both electrocatalysts and supports. Considering the above and given the climate problems that the planet is going through, the development of sustainable and environmentally friendly materials is essential, with the production of electrocatalysts from renewable inorganic substances obtained from biomass resources. Furthermore, being capable of convert a bio-waste into an effective electrocatalyst will represent a breakthrough in the field.  In this work, a straight-forward route is presented to obtain porous carbons from residues of Posidonia oceanica fibres doped with Nitrogen (N) and Iron (Fe) to be used as electrocatalysts for ORR. Posidonia oceanica is a grass from the Mediterranean Sea that usually accumulates in large quantities on the coasts, making it necessary to remove it from the beaches during tourist season. Therefore, Posidonia have become a problem that overload the capacity of the Mediterranean dumps and requires a solution. In this sense, exploring the viability of using Posidonia as precursor to create new electrocatalysts could partially solve this problem [2].

Using a waste to produce new catalysts is not worthy unless a suitable and environmentally friendly synthesis method is used. For this reason, hydrothermal treatment assisted with H₃PO₄ has been used, followed by carbonization. The N have been incorporated using a melamine precursor in a subsequent pyrolysis. To add Fe to the C-N material a two-step process has been used, where C-N support is prepared by pyrolysis in the presence of a Mg²⁺ salt, which is used as an active site template and porogen. Subsequently, the C-N materials obtained have been washed with HCl to eliminate the Mg species and free the active sites for the Fe coordination. The Fe-N-C materials have been prepared by the wet impregnation method in methanol reflux using FeCl₂ as Fe precursor. The Fe-N-C electrocatalysts have been tested in the oxygen reduction reaction in basic media (0.1 M KOH) in a Rotating Disk Electrode (RDE) configuration and its catalytic activity has been compared to the commercial Fe-N-C electrocatalyst.