Abstract
The exploration of highly efficient catalysts to replace noble metal platinum for the oxygen reduction reaction, on which M/N/C catalysts have shed brilliant light, is greatly significant but challenging. This paper presents a strategy for synthesizing highly efficient and stabilized hollow structure Fe/N/C catalysts with iron and nitrogen doped into the carbon layer by the self-template method. The prepared Fe/N/C catalysts with NaCl protection during pyrolysis are characterized by a unique hollow structure, porous morphology and Fe-N coordination as the active sites, all of which significantly endow the materials with excellent properties towards the ORR, including high electrical conductivity, long-term durability and outstanding capacity for methanol tolerance. We employed X-ray absorption fine structure spectrometry to investigate the chemical state and coordination environment of the central iron atoms of the Fe/N/C catalysts, which also clarified the promoting effect of the NaCl protection for Fe-N coordination during pyrolysis. In particular, the Fe/N/C catalysts exhibit positive half-wave potentials (0.84 V vs. RHE) and Tafel slope comparable to 20% commercial Pt/C, possessing four-electron transfer pathway as well as excellent long-term stability and methanol tolerance in alkaline medium.