Effect on Oxygen Reduction Reaction of Iron Catalyst Synthesized by Aniline Monomer-Mediated Technique

An anion exchange membrane fuel cell (AEMFC), which uses hydroxyl conductive membranes instead of proton conductive ones, is highlighted as a replacement for a proton exchange membrane fuel cell. AEMFC has the advantage of using abundant and inexpensive transition metals, such as iron, cobalt, and nickel for catalysts owing to mild reaction conditions. Among numerous non-platinum metal catalysts (NPMCs), M-N-C catalyst has been reported considerably and Fe-N-C catalyst, which co-doped nitrogen and Fe, was considered the promising M-N-C owing to their high atomic utilization and excellent electrocatalytic performance. For the Fe-N-C catalyst, it is important to expose the maximum number of active sites and distribute the Fe in the Fe-N-C catalyst uniformly on a carbon support. Therefore, many researchers have been exploring Fe-N-C catalyst, in which Fe exist as a single atom. The common method for synthesizing single atom Fe-N-C includes the random mixing and high-temperature pyrolysis process, which tends to cause the aggregation of metals and leads to the degradation of catalytic activity. Thus, the research for preventing the aggregation of metals is crucial for high electrocatalytic activity.<br/><br/>This study explores the possibility of applying M-N-C to AEMFC through the development of Fe single atom. We adopted the method of aniline-mediated metal reduction and high-temperature pyrolysis for synthesizing the Fe-N-C catalyst. The Fe single atom reported high performance and durability and possess the optimal Fe-N_x coordination structure by optimizing the synthesis condition. The optimization of the synthesis conditions for the Fe-N-C catalyst proceeds through the control of the amount of Fe precursor and aniline and the temperature of pyrolysis. Several characterizations such as Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Inductively coupled plasma-mass spectrometry (ICP-MS), and Scanning transmission electron microscopy (STEM) were introduced to investigate the catalyst properties. The uniform distribution of the single atom on the carbon support was confirmed by STEM and XRD, and the Fe content was checked to be about 1wt.% using ICP-MS and TGA. Furthermore, electrochemical measurements were conducted to present the correlation between catalytic activity and structure. The catalyst, which possesses single atom active sites, showed high electrochemical performance and durability for oxygen reduction reaction and proposed the applicability for AEMFC. The study proved that the Fe single-atom catalyst was successfully synthesized by metal reduction and pyrolysis processes