Host-guest interactions promoted formation of Fe-N4 active site toward efficient oxygen reduction reaction catalysis

Fe-N-C is the most promising material to replace the noble metal catalyst for cathodic oxygen reduction reaction in proton exchange membrane fuel cells (PEMFCs). However, the practical performance of Fe-N-C catalyst is significantly limited by its low active site (Fe-N-4) density. Herein, we propose to promote the formation of Fe-N-4 active sites in Fe-N-C catalyst by strengthening the interaction of N precursors and Fe precursors during the carbonization synthesis. In our approach, ionic liquid (IL, [EMIM] [NTf2]) with high nitrogen content and good thermal stability is caged in the pores of Fe-ZIF-8 through the host-guest interactions. These interactions are critical for the preservation of Fe and N species and formation of active sites during the synthesis. The optimal catalyst developed with this approach (Fe-0.05-N-C/10) has a high density of accessible Fe-N4 sites (1.88*1019 sites g(-1)). Therefore, in both acidic and alkaline media, Fe-0.05-N-C/10 showed excellent ORR activity comparable to commercial Pt/C catalyst. Moreover, PEMFC performance with a peak power density of 300 mW cm(-2) was demonstrated with Fe-0.05-N-C/10 under H-2/O-2 conditions. The synthetic approach reported herein may be used for tailoring of advanced catalyst with high intrinsic activity. (c) 2022 Elsevier Inc. All rights reserved.