MIL‐101‐Derived Mesoporous Carbon Supporting Highly Exposed Fe Single‐Atom Sites as Efficient Oxygen Reduction Reaction Catalysts
Xiaoying Xie, Lishan Peng, Hongzhou Yang, Geoffrey I. N. Waterhouse, Lu Shang, Tierui Zhang
Abstract
Abstract Fe single‐atom catalysts (Fe SACs) with atomic FeN x active sites are very promising alternatives to platinum‐based catalysts for the oxygen reduction reaction (ORR). The pyrolysis of metal–organic frameworks (MOFs) is a common approach for preparing Fe SACs, though most MOF‐derived catalysts reported to date are microporous and thus suffer from poor mass transfer and a high proportion of catalytically inaccessible FeN x active sites. Herein, NH 2 ‐MIL‐101(Al), a MOF possessing a mesoporous cage architecture, is used as the precursor to prepare a series of N‐doped carbon supports (denoted herein as NC‐MIL101‐T) with a well‐defined mesoporous structure at different pyrolysis temperatures. The NC‐MIL101‐T supports are then impregnated with a Fe(II)‐phenanthroline complex, and heated again to yield Fe SAC‐MIL101‐T catalysts rich in accessible FeN x single atom sites. The best performing Fe SAC‐MIL101‐1000 catalyst offers outstanding ORR activity in alkaline media, evidenced by an ORR half‐wave potential of 0.94 V (vs RHE) in 0.1 m KOH, as well as excellent performance in both aqueous primary zinc–air batteries (a near maximum theoretical energy density of 984.2 Wh kg Zn −1 ) and solid‐state zinc–air batteries (a peak power density of 50.6 mW cm −2 and a specific capacity of 724.0 mAh kg Zn −1 ).