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Iron atom-cluster interactions increase activity and improve durability in Fe-N-C fuel cells.

ABSTRACT: Simultaneously increasing the activity and stability of the single-atom active sites of M-N-C catalysts is critical but remains a great challenge. Here, we report an Fe-N-C catalyst with nitrogen-coordinated iron clusters and closely surrounding Fe-N₄ active sites for oxygen reduction reaction in acidic fuel cells. A strong electronic interaction is built between iron clusters and satellite Fe-N₄ due to unblocked electron transfer pathways and very short interacting distances. The iron clusters optimize the adsorption strength of oxygen reduction intermediates on Fe-N₄ and also shorten the bond amplitude of Fe-N₄ with incoherent vibrations. As a result, both the activity and stability of Fe-N₄ sites are increased by about 60% in terms of turnover frequency and demetalation resistance. This work shows the great potential of strong electronic interactions between multiphase metal species for improvements of single-atom catalysts.

SUBMITTER: Wan X

PROVIDER: S-EPMC9135695 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Iron atom-cluster interactions increase activity and improve durability in Fe-N-C fuel cells.

Wan Xin X Liu Qingtao Q Liu Jieyuan J Liu Shiyuan S Liu Xiaofang X Zheng Lirong L Shang Jiaxiang J Yu Ronghai R Shui Jianglan J

Nature communications 20220526 1

Simultaneously increasing the activity and stability of the single-atom active sites of M-N-C catalysts is critical but remains a great challenge. Here, we report an Fe-N-C catalyst with nitrogen-coordinated iron clusters and closely surrounding Fe-N<sub>4</sub> active sites for oxygen reduction reaction in acidic fuel cells. A strong electronic interaction is built between iron clusters and satellite Fe-N<sub>4</sub> due to unblocked electron transfer pathways and very short interacting distanc ...[more]

PMID: 35618792

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Project description:Frataxin, a mitochondrial protein that is directly involved in regulating cellular iron homeostasis, has been suggested to serve as an iron chaperone during cellular Fe-S cluster biosynthesis. In humans, decreased amounts or impaired function of frataxin causes the autosomal recessive neurodegenerative disorder Friedreich's ataxia. Cellular production of Fe-S clusters is accomplished by the Fe cofactor assembly platform enzymes Isu (eukaryotes) and IscU (prokaryotes). In this report, we have characterized the overall stability and iron binding properties of the Drosophila frataxin homologue (Dfh). Dfh is highly folded with secondary structural elements consistent with the structurally characterized frataxin orthologs. While the melting temperature ( T M approximately 59 degrees C) and chemical stability ([urea] 50% approximately 2.4 M) of Drosophila frataxin, measured using circular dichroism (CD) and fluorescence spectroscopy, closely match values determined for the human ortholog, pure Dfh is more stable against autodegradation than both the human and yeast proteins. The ferrous iron binding affinity ( K d approximately 6.0 microM) and optimal metal to protein stoichiometry (1:1) for Dfh have been measured using isothermal titration calorimetry (ITC). Under anaerobic conditions with salt present, holo-Dfh is a stable iron-loaded protein monomer. Frataxin prevents reactive oxygen species-induced oxidative damage to DNA when presented with both Fe(II) and H 2O 2. Ferrous iron bound to Dfh is high-spin and held in a partially symmetric Fe-(O/N) 6 coordination environment, as determined by X-ray absorption spectroscopy (XAS). Extended X-ray absorption fine structure (EXAFS) simulations indicate the average Fe-O/N bond length in Dfh is 2.13 A, consistent with a ligand geometry constructed by water and carboxylate oxygens most likely supplied in part by surface-exposed conserved acidic residues located on helix 1 and strand 1 in the structurally characterized frataxin orthologs. The iron-dependent binding affinity ( K d approximately 0.21 microM) and optimal holo-Dfh to Isu monomer stoichiometry (1:1) have also been determined using ITC. Finally, frataxin mediates the delivery of Fe(II) to Isu, promoting Fe-S cluster assembly in vitro. The Dfh-assisted assembly of Fe-S clusters occurs with an observed kinetic rate constant ( k obs) of 0.096 min (-1).

Dataset Information

Iron atom-cluster interactions increase activity and improve durability in Fe-N-C fuel cells.

Publications

Iron atom-cluster interactions increase activity and improve durability in Fe-N-C fuel cells.

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