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 Fe₃C/C and Fe₂N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15% CH₄/H₂ and pure NH₃, respectively. By acid leaching of Fe₂N/C sample, only single sites of FeN₄ species were presented, providing an ideal model for identification of catalytic functions of the single sites of FeN₄ in ORR. A correlation was conducted between the concentration of Fe^IIN₄ in low spin state by Mössbauer 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^IIN₄ species as highly active sites for the ORR.

近年来，已经认识到Fe-NC物质的催化材料对氧还原反应（ORR）具有活性。然而，活性位点的鉴定仍然具有挑战性，因为它通常涉及热解过程并获得混合组分。在此，通过温度编程分别还原Fe前驱体在15％CH ₄ / H ₂和纯NH ₃中的合成Fe ₃ C / C和Fe ₂ N / C样品。通过Fe ₂ N / C样品的酸浸，仅显示了FeN ₄物种的单个位点，为鉴定FeN ₄单个位点的催化功能提供了理想的模型在ORR中。通过Mössbauer光谱在低自旋态下的Fe ^II N ₄浓度与碱性介质在0.8 V下的动电流密度之间建立了相关性，这种结构-性能相关性确保了低自旋Fe ^II N ₄物种的催化作用作为ORR高度活跃的网站。