Molten-salt-assisted thermal emitting method to transform bulk Fe2O3 into Fe single atom catalysts for oxygen reduction reaction in Zn-air battery

Abstract

Efficient, durable and low-cost electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics are urgently needed for the energy conversion techniques, such as metal-air batteries and fuel cells. In this work, we develop a molten-salt-assisted thermal emitting approach to transform the cheap and easily obtainable bulk ferric (III) oxide powder into a highly efficient Fe single atom catalyst for cathodic oxygen reduction reaction. Benefiting from the strong polarity force of ionized cations and anions, the molten salt effectively facilitates breakage of chemical bonding in bulk Fe2O3 and volatilization of Fe species far below the melting point of Fe2O3 (1841 K), lowering the consumption of energy and time needed in the synthetic procedure. The vaporized Fe species are subsequently anchored onto the surface of nitrogen-doped porous carbon, evolving the single-atom “Fe-N4-O2” site catalyst. The obtained catalyst presents an excellent oxygen reduction reaction performance with half-wave potential of 0.896 V vs RHE in alkaline media, comparable to the most efficient non-precious metal catalysts and outperforming the benchmark system Pt/C. Furthermore, this method is demonstrated to be valid for synthesis of non-noble-metal single atom catalysts (metal = Co, Mn, Cu, Ni) by changing different metal oxides precursors.