The use of different types of reduced graphene oxide in the preparation of Fe-N-C electrocatalysts: capacitive behavior and oxygen reduction reaction activity in alkaline medium

Three different types of reduced graphene oxide (rGO) were prepared starting from graphite oxide (GO) produced with the Hummers’ method using three different exfoliation-reduction strategies: thermal annealing under N2 atmosphere at 700 °C, thermal annealing under H2–N2 (1:1 vol.) atmosphere at 500 °C and ultrasonication. Then, three non-noble metal catalysts (NNMC) for the oxygen reduction reaction (ORR) were synthesized using these three different rGO as carbon supports, by impregnation of a complex formed between Fe(II) ions and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ) as source of nitrogen, followed by a pyrolysis at 800 °C. The physical-chemical properties of rGO and Fe-N/rGO catalysts were characterized by N2 physisorption, XRD, XPS, SEM, and EDX. The capacitive behavior and the ORR activity of rGO and Fe-N/rGO catalysts were measured in alkaline conditions by cyclic voltammetry (CV) and rotating disk electrode (RDE), respectively. The three different reduction-exfoliation methods used for the rGO preparation influenced the physical-chemical properties, as well as the capacitive currents and the ORR activity of both rGO and Fe-N/rGO. This provides an insight about which synthesis process could be the most convenient for the final application.