A nitrogen and sulfur co-doped iron-based electrocatalyst derived from iron and biomass ligand towards the oxygen reduction reaction in alkaline media

Research on highly efficient nitrogen and sulfur co-doped carbon materials is crucial for the development of Fe-based non-noble metal electrocatalysts (NNMEs) as alternatives to platinum-group metal-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. In this work, complexes were derived from iron salt and biomass ligands, subsequently mixed with active carbon nanoparticles (NPs) and pyrolyzed at 800 °C to obtain the resulting electrocatalysts Fe/NSC (800) and Fe/NC (800). Through screening the synthetic parameters, it was found that the N and S co-decorated Fe-based electrocatalyst of Fe/NSC (800) displays better ORR performances in terms of the onset potential (Eonset) and the half-wave potential (E1/2) than those of the Fe-free electrocatalyst of NSC (800) and the N-doped electrocatalyst of Fe/NC (800). The improved ORR activity can be mainly ascribed to the FeN4 active sites, as well as the additional S-doping within the carbon matrixes. Additionally, Fe/NSC (800) displays good durability superior to that of 20 wt% Pt/C in 0.1 M KOH solution. This synthetic approach is beneficial for the synthesis of NNMEs with biomass ligands for boosting the ORR performances in an alkaline solution.