A template-free route to a Fe3O4–Co3O4 yolk–shell nanostructure as a noble-metal free electrocatalyst for ORR in alkaline media

Abstract

This paper reported a facile template-free route to prepare hierarchical Fe₃O₄–Co₃O₄ yolk–shell nanostructures. These highly porous architectures, with a diameter of about 2 μm, were assembled from Co₃O₄ flower-like shells and Fe₃O₄ sphere core. A series of experiments with different conditions were carried out to determine the key factors in this typical solvothermal synthesis that led to the formation of the obtained yolk–shell nanostructures, and a possible growth mechanism was proposed. Sequentially, some other similar metal oxide nanostructures were also obtained in this way. Importantly, the obtained Fe₃O₄–Co₃O₄ yolk–shell nanostructures exhibit excellent electrocatalytic ORR performance. The half-wave potential of the yolk–shell nanostructures is about 5 and 80 mV positive-shifted compared to that of the independent Co₃O₄ and Fe₃O₄ nanoparticles. The current density of O₂ reduction for the Fe₃O₄–Co₃O₄ yolk–shell nanostructures is also much higher than that of Co₃O₄ and Fe₃O₄ nanoparticles. The enhanced electrocatalytic performance for Fe₃O₄–Co₃O₄ yolk–shell nanostructures may make them available to be an efficient and cheap noble-metal free cathodic catalyst for PEMFCs.