Engineering Favorable Morphology and Structure of Fe‐N‐C Oxygen‐Reduction Catalysts through Tuning of Nitrogen/Carbon Precursors. Issue 4 (27th January 2017)

• Record Type: Journal Article
• Authors: Gupta, Shiva; Zhao, Shuai; Ogoke, Ogechi; Lin, Ye; Xu, Hui; Wu, Gang
• Is Part Of: ChemSusChem. Volume 10:Issue 4(2017)
• Page Start: 774
• Page End: 785
• Publication Date: 2017-01-27
• Subjects: electrocatalysis -- nonprecious metals -- oxygen reduction reaction -- polyaniline -- precursors; Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.201601397
• Languages: English
• ISSNs: 1864-5631

Abstract

Abstract: Structures and morphologies of Fe‐N‐C catalysts are believed to be crucial because of the number of active sites and local bonding structures governing the overall catalyst performance for the oxygen reduction reaction (ORR). However, the knowledge how to rationally design catalysts is still lacking. By combining different nitrogen/carbon precursors, including polyaniline (PANI), dicyandiamide (DCDA), and melamine (MLMN), we aim to tune catalyst morphology and structure to facilitate the ORR. Instead of the commonly studied single precursors, multiple precursors were used during the synthesis; this provides a new opportunity to promote catalyst activity and stability through a likely synergistic effect. The best‐performing Fe‐N‐C catalyst derived from PANI+DCDA is superior to the individual PANI or DCDA‐derived ones. In particular, when compared to the extensively explored PANI‐derived catalysts, the binary precursors have an increased half‐wave potential of 0.83 V and an enhanced electrochemical stability in challenging acidic media, indicating a significantly increased number of active sites and strengthened local bonding structures. Multiple key factors associated with the observed promotion are elucidated, including the optimal pore size distribution, highest electrochemically active surface area, presence of dominant amorphous carbon, and thick graphitic carbon layers with more pyridinic nitrogen edge sites likely bonded with active atomic iron. Abstract : Multiple precursors for ORR : The most favorable morphology and structure of Fe‐N‐C as catalyst for the oxygen reduction reaction are elucidated by tuning the nitrogen/carbon precursors. The favorable features in catalysts include an amorphous carbon phase with a low degree of graphitization, abundant microporosity, and thick graphitic carbon layers capable of accommodating a large number of active sites likely associated with pyridinic nitrogen atoms and atomic iron exposed at the carbon edges.