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Article Dans Une Revue Advanced Materials Année : 2023

FeNC oxygen reduction electrocatalyst with high utilisation penta‐coordinated sites

Saurav Ch. Sarma
Alexander Bagger
Silvia Favero
Ricardo Garcia-Serres
Alain Li

Résumé

Atomic Fe in N-doped carbon (FeNC) electrocatalysts for oxygen (O$_2$) reduction at the cathode of proton exchange membrane fuel cells (PEMFCs) are the most promising alternative to platinum-group-metal catalysts. Despite recent progress on atomic FeNC O$_2$ reduction, their controlled synthesis and stability for practical applications remains challenging. A two-step synthesis approach has recently led to significant advances in terms of Fe-loading and mass activity; however, the Fe utilisation remains low owing to the difficulty of building scaffolds with sufficient porosity that electrochemically exposes the active sites. Herein, we addressed this issue by coordinating Fe in a highly porous nitrogen doped carbon support (~3295 m$^2$ g$^{-1}$), prepared by pyrolysis of inexpensive 2,4,6triaminopyrimidine and a Mg$^{2+}$ salt active site template and porogen. Upon Fe coordination, a high electrochemical active site density of 2.54×10$^{19}$ sites g$_{FeNC}$$^{-1}$ and a record 52% FeN$_x$ electrochemical utilisation based on in situ nitrite stripping was achieved. The Fe single atoms are characterised pre-and post-electrochemical accelerated stress testing by aberration-corrected high-angle annular dark field scanning transmission electron microscopy, showing no Fe clustering. Moreover, ex situ X-ray absorption spectroscopy and low-temperature Mössbauer spectroscopy suggest the presence of penta-coordinated Fe sites, which were further studied by density functional theory calculations.

Domaines

Matériaux
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Dates et versions

hal-03984630 , version 1 (13-02-2023)

Identifiants

Citer

Jesús Barrio, Angus Pedersen, Saurav Ch. Sarma, Alexander Bagger, Mengjun Gong, et al.. FeNC oxygen reduction electrocatalyst with high utilisation penta‐coordinated sites. Advanced Materials, 2023, 35 (14), pp.2211022. ⟨10.1002/adma.202211022⟩. ⟨hal-03984630⟩
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