▎ 摘　　要

Oxygen reduction reactions (ORRs) occur at cathodes in fuel cells and require efficient electrocatalysts. Because of the cost and limited durability and stability of commercial Pt/C catalysts, the development of efficient Pt-free electrocatalysts is an active research topic. Here, we describe the solution-based production of Fe3O4 nanoparticles/N-doped graphene-based materials from FeCl2, graphene oxide (G-O), and hydrazine. Orders of production steps were varied by; i) reacting FeCl2 and G-O first and then adding hydrazine (Fe/G-N), ii) reacting G-O, FeCl2, and hydrazine at the same time (Fe/G/N), or iii) reacting G-O and hydrazine first and then adding FeCl2 (G/N-Fe). The hybrids produced showed better ORR electrocatalytic activity in alkaline media than single components such as N-doped graphene-based materials or Fe3O4. Furthermore, the electrocatalytic properties of the resulting hybrids were found to depend on orders of addition. Fe/G/N was found to be the best electrocatalyst and had better onset and half-wave potentials, thermodynamic current density, and 4-electron selectivity. All three hybrids show good cyclic durability and methanol tolerance.