Recent advances and prospects of iron-based noble metal-free catalysts for oxygen reduction reaction in acidic environment: A mini review

The oxygen reduction reaction (ORR) occurred in acidic media, as the cathode reaction of proton exchange membrane fuel cells (PEMFCs) with great commercialization potential, has attracted much attention. However, the slow kinetics of ORR and the high cost of cathode catalysts (mainly platinum (Pt)-based materials in current) have become the main obstacle to the rapid development of PEMFCs. Therefore, the exploration of efficient and inexpensive non-precious metal-based ORR catalysts has emerged as an urgent issue. Non-noble transition metal-based materials have been widely investigated as ORR catalysts in acidic media. This review focused on the investigation of iron (Fe) based catalysts in acidic ORR processes. In this review, the ORR mechanism was first introduced. Subsequently, the fabrication method of Fe-based catalysts by co-pyrolysis of mixtures containing Fe, non-metal, and organic precursors was discussed. Finally, the recent advances of Fe-based materials (carbides, nitrides, oxides, phosphides, chalcogenides, hybrids, alloys and single atom catalysts) as acidic ORR catalysts were summarized, and mainly focused on catalytic performance, stability and catalytic mechanism studies with Density Functional Theory (DFT) calculation. Finally, the challenges and future perspectives of Fe-based catalysts were also proposed.