In‐Situ Silica Xerogel Assisted Facile Synthesis of Fe‐N‐C Catalysts with Dense Fe‐N_x Active Sites for Efficient Oxygen Reduction

Abstract

In the past decade, atomically dispersed Fe active sites (coordinated with nitrogen) on carbon materials (FeNC) have emerged rapidly as promising single‐atom catalysts (SACs) for the oxygen reduction reaction (ORR) to substitute precious group metal (PGM) catalysts, owing to their earth abundance and low cost. Nonetheless, the production of highly active FeNC SACs is largely restricted by material cost, low product yield and difficulty of microstructure design. Herein, the authors demonstrate a facile in‐situ xerogel (ISG) assisted synthetic strategy, using cheap materials, to construct FeNC SACs (ISG FeNC). The porous silica xerogel, formed in‐situ with the FeNC precursors, encourages the emergence of enormous micropores/mesopores and homogeneous confinement/protection to the precursors during pyrolysis, benefiting to the formation of abundant accessible active sites (27.6 × 1019 sites g–1). Correspondingly, the ISG FeNC exhibits excellent ORR activity with a half‐wave potential (E1/2 = 0.91 V) in alkaline medium. The Zn–air battery assembled using the ISG FeNC SACs as the bifunctional catalyst of air cathode, demonstrates commendable performance with high peak power density of 249.1 mW cm–2 and superior long‐term stability (660 cycles with 220 h). This work offers an economic and efficient way to fabricate PGM‐free SACs for diverse applications.

Engineering g-C3N4 composited Fe-UIO-66 to in situ generate robust single-atom Fe sites for high-performance PEMFC and Zn–air battery

“…have shown their promising potential in replacing the conventional noble metal cathode catalysts. [12][13][14][15][16][17][18][19][20][21][22] Several research groups have also achieved several exciting breakthroughs. For example, Sun et al 23 reported a Fe/N/C ORR catalyst prepared by pyrolysis under NH 3 that exhibited a half-wave potential of 0.78 V in 0.1 M HClO 4 .…”

How pH Affects the Oxygen Reduction Reactivity of Fe–N–C Materials

“…Although Pt-group metal (PGM)-based catalysts display considerable ORR activity and enable the practical implementation of fuel-cell technologies, their high cost, low availability, and consequent sustainability issues severely hinder their potential in commercial applications. − Substantial efforts have been made toward the development of PGM-free materials, and among which, metal–nitrogen–carbon (M–N–C) catalysts that include dispersed earth-abundant metal atoms (e.g., Fe, Co, and Mn) have become increasingly popular. − Such novel catalysts exhibit high per-site ORR activity and tolerance toward CO and CH 3 OH . In particular, Fe–N–C catalysts have been established as one of the most promising candidates, − but there is still much room for improvement in ORR activity. , To improve their ORR performance, an in-depth understanding of the underlying reaction mechanisms of Fe–N–C catalysts is of vital importance.…”

Kinetically favorable edge-type iron–cobalt atomic pair sites synthesized via a silica xerogel approach for efficient bifunctional oxygen electrocatalysis

“…Recently, atomically dispersed transition metals coordinated with nitrogen distributed on carbon materials (M-NC), known as single-atom catalysts (SACs), have captivated increasing research interest for ORR catalysis as they possess advantages of low material cost and high catalytic activity, the latter of which benets from the high atom utilization and easily accessible active sites. [7][8][9] A vast array of synthetic strategies, including metal-organic frameworks (MOFs), wet impregnation and precipitation approaches, [10][11][12][13] have been developed for the preparation of SACs. Despite these signicant achievements, challenges, such as complicated synthetic routes and low product yields still severely restrict the large-scale production of high-performance SACs.…”