11.
Over recent years,catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction(ORR).However,the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained.Herein Fe
3C/C and Fe
2N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15%CH
4/H
2and pure NH
3,respectively.By acid leaching of Fe
2N/C sample,only single sites of FeN
4species were presented,providing an ideal model for identification of catalytic functions of the single sites of FeN
4in ORR.A correlation was conducted between the concentration of Fe
ⅡN
4in low spin state by Mossbauer spectra and the kinetic current density at 0.8 V in alkaline media,and such a structure-performance correlation assures the catalytic roles of low spin Fe
ⅡN
4 species as highly active sites for the ORR.
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