FeNC Electrocatalysts with Densely Accessible FeN₄ Sites for Efficient Oxygen Reduction Reaction

Abstract

The development of iron and nitrogen co‐doped carbon (FeNC) electrocatalysts for the oxygen reduction reaction (ORR) in proton‐exchange membrane fuel cells (PEMFCs) is a grand challenge due to the low density of accessible FeN4 sites. Here, an in situ trapping strategy using nitrogen‐rich molecules (e.g., melamine, MA) is demonstrated to enhance the amount of accessible FeN4 sites in FeNC electrocatalysts. The melamine molecules can participate in the coordination of Fe ions in zeolitic imidazolate frameworks to form FeN6 sites within precursors. These FeN6 sites are then converted into atomically dispersed FeN4 sites during a pyrolytic process. Remarkably, the FeNC/MA exhibits a high single‐atom Fe content (3.5 wt.%), a large surface area (1160 m2 g−1), and a high density of accessible FeN4 sites (45.7 × 1019 sites g−1). As a result, FeNC/MA shows a much enhanced ORR activity with a half‐wave potential of 0.83 V (vs the reversible hydrogen electrode) in a 0.5 m H2SO4 electrolyte solution and a good performance in a PEMFC system with an activity of 80 mA cm−2 at 0.8 V under 1.0 bar H2/air. This work offers a promising approach toward high‐performance carbon‐based ORR electrocatalysts.

Alloying Co Species into Ordered and Interconnected Macroporous Carbon Polyhedra for Efficient Oxygen Reduction Reaction in Rechargeable Zinc–Air Batteries

“…The oxygen reduction reaction (ORR) is a crucial electrochemical process that occurs in rechargeable metal–air batteries, fuel cells, and other energy conversion and storage devices. [ 1–5 ] However, the sluggish kinetics of the ORR, which involves four electron and proton transfer steps, seriously restricts the overall energy conversion efficiency of these devices. Currently, noble Pt‐based materials are regarded as state‐of‐the‐art electrocatalysts for the sluggish ORR.…”

“…The oxygen reduction reaction (ORR) is a crucial electrochemical process that occurs in rechargeable metal-air batteries, fuel cells, and other energy conversion and storage devices. [1][2][3][4][5] However, the sluggish kinetics of the ORR, which involves four electron and proton transfer steps, seriously restricts the a hydrogel-derived process and found that it exhibited higher ORR activity than Co/PFC or Ni/PFC. [10] Su et al investigated the synergistic effect of Fe and Co in TM@N-C catalysts, demonstrating that alloying generates a favorable electronic environment on the surface of the material and thus improves its ORR activity.…”

Theory‐Guided Regulation of FeN4Spin State by Neighboring Cu Atoms for Enhanced Oxygen Reduction Electrocatalysis in Flexible Metal–Air Batteries

“…Generally, single metal atoms are more likely captured by graphitic carbon with rich nanopores due to abundant defects by heteroatom doping [8, 16, 35–38] . In the present study, three structures of the FeN 4 sites are considered computationally that are situated at different locations of a graphene sheet (details in the Supporting Information), on the basal plane (Fe 1 ‐1, panel (i) in Figure 1a), at the nanopore edge (Fe 1 ‐2, panel (ii) in Figure 1a), and adjacent to the nanopore (Fe 1 ‐3, Figure S1).…”

Rugae‐like N‐doped porous carbon incorporated with Fe‐N x and Fe 3 O 4 dual active sites as a powerful oxygen reduction catalyst for zinc‐air batteries

“…The success of N doping into carbon matrix was verified by the C N bond. 62 High-resolution N 1s spectrum displayed four component peaks at 397.8 (pyridinic N, 48.78%), 399.1 (Fe-N x , 9.80%), 63,64 400.2 (pyrrolic N, 29.13%), 401.8 eV (graphitic N, 8.85%), and 403.5 eV (oxidized N, 3.44%), proving that N was successfully doped into the carbon skeletons (Figure 3C). 65 By coordinating with pyridineand pyrrole-N, Fe can form atomically dispersed Fe-N x species.…”