The Role of Polyaniline Molecular Structure in Producing High‐Performance Fe‐N‐C Catalysts for Oxygen Reduction Reaction. Issue 27 (22nd July 2019)

• Record Type: Journal Article
• Authors: He, Qian; Chen, Xiuhong; Jia, Fengqiu; Ding, Wei; Zhou, Yuanyuan; Wang, Jian; Song, Xiaoyun; Jiang, Jinxia; Liao, Qiang; Li, Jing; Wei, Zidong
• Is Part Of: ChemistrySelect. Volume 4:Issue 27(2019)
• Page Start: 8135
• Page End: 8141
• Publication Date: 2019-07-22
• Subjects: fuel cell -- oxygen reduction reaction -- metal-N−C -- polyaniline -- molecular structures; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201901329
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: The precise control of nano‐structure and increase active sites density are of crucial importance for the pyrolyzed Fe‐N−C catalysts′ performance optimization. Herein, the relationship between molecular structures of PANI precursors and the activity for oxygen reduction reaction (ORR) of the derived Fe‐N−C catalysts is investigated. The PANI molecular structure, especially the content of quinoid rings (QR), is controlled by varying molar ratios of ammonium persulfate (APS) to aniline monomers (AN). With the increase of APS/AN ratio from 0.5 to 4, the oxidation degree together with the QR content of PANI increases. Accordingly, the produced catalysts' morphology experiences an evolution from bulk, nanotube to flower‐like structure. And the ORR activity shows volcano‐relationship with the increase of the QR content in PANI precursors. Specifically, when APS/AN=2.5, the derived PANI with moderate QR content benefits to produce Fe‐N−C catalyst which shows the maximum ORR activity with a half‐wave potential of 0.74 V (vs RHE) in acidic electrolyte among the produced catalysts. Moreover, two opposite effects with the increasing QR content are revealed; i) the QR benefits the Fe coordination and Fe−Nx active sites formation which enhances the activity, and ii) the accompanying formed oligomers decrease the thermal stability and thus decrease the number of active sites. Abstract : Using different APS/AN ratio obtains PANI with different quinoid rings (QR) contents in PANI molecules. Pyrolyzation of these PANI and FeCl3 derives catalysts whose morphologies change from bulk, nanorods to flower‐like(see picture). QR benefits the Fe coordination and Fe−Nx active sites formation, but accompanying formed oligomers decrease the thermal stability and the amount of active site. Hence the ORR activity shows volcano shaped dependence on the QR content.