Microporous Framework Induced Synthesis of Single-Atom Dispersed Fe-N-C Acidic ORR Catalyst and Its in Situ Reduced Fe-N<sub>4</sub> Active Site Identification Revealed by X-ray Absorption Spectroscopy

Xiao, Meiling; Zhu, Jianbing; Ma, Liang; Zhao, Jianmin; Ge, Junjie; Deng, Xinyang; Hou, Yang; He, Qinggang; Li, Jingkun; Jia, Qingying; Mukerjee, Sanjeev; Yang, Ruoou; Jiang, Zheng; Su, Dangsheng; Liu, Changpeng; Wang, Xing

doi:10.1021/acscatal.8b00138

Cited by 473 publications

(321 citation statements)

References 60 publications

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“…The activity gap between the state-of-the-art Pt/C and the best performing SA-Fe-N-1.5-800 catalyst, as reflected by the difference of E 1/2 , has been substantially reduced to ≈30 mV (0.841 vs 0.812 V vs RHE). [38] In this study, assuming that all the surface Fe atoms contribute to the ORR activity, the average TOF at 0.8 V is calculated to be 1.785 e s −1 sites −1 . [2,[35][36][37] The ORR activity of SA-Fe-N-1.5-800 is also superior to that of Fe-N-KJ-800 ( Figure S12, Supporting Information), further confirming the advantages of using SA as a Fe immobilizer and carbon source for developing M-N-C catalysts relative to traditional carbon supports.…”

mentioning

confidence: 96%

Atomically Dispersed Fe‐N_x/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy

Miao

Wang

Tsai

et al. 2018

Advanced Energy Materials

233

114

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the-state-of-the-art ORR catalysts but their uses are largely restricted by the prohibitive cost and limited activity/stability. [3][4][5][6][7] In this regard, the development of non-Pt group metal (non-PGM) catalysts derived from earth-abundant elements for ORR is the fundamental solution for the widespread applications of PEMFCs. [8][9][10] Among various non-PGM ORR catalysts developed in last decade, transition metalnitrogen-carbon (M-N-C) catalysts with M-N x coordination active sites embedded in the basal planes of carbon matrixes were the most promising ones due to their decent activity in both acidic and alkaline media and ease of scale-up production. [11][12][13][14][15] The ORR performance of M-N-C electrocatalysts in alkaline electrolyte has been well demonstrated notwithstanding, [9,[16][17][18][19][20] their performance in acidic environment is still deficient and often degrades rapidly due to the etching of metal species and/or decomposition of active sites. [21,22] Generally, the M-N-C catalysts are prepared via high-temperature (T > 800 °C) pyrolysis process of transition metal (e.g., Fe, Co, Ni), nitrogen, and carbon precursors, during which the metal atoms are very easy to agglomerate into large particles. The aggregated metal and metal oxide/carbide particles will hinder the accessibility of M-N x /C active sites and lower the utilization of M atoms seriously, thus compromising their ORR activity. Furthermore, metal aggregates will be easily etched away in acid, leading to The development of high-performance oxygen reduction reaction (ORR) catalysts derived from non-Pt group metals (non-PGMs) is urgent for the wide applications of proton exchange membrane fuel cells (PEMFCs). In this work, a facile and cost-efficient supramolecular route is developed for making non-PGM ORR catalyst with atomically dispersed Fe-N x /C sites through pyrolyzing the metal-organic polymer coordinative hydrogel formed between Fe 3+ and α-L-guluronate blocks of sodium alginate (SA). High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption spectroscopy (XAS) verify that Fe atoms achieve atomic-level dispersion on the obtained SA-Fe-N nanosheets and a possible fourfold coordination with N atoms. The best-performing SA-Fe-N catalyst exhibits excellentORR activity with half-wave potential (E 1/2 ) of 0.812 and 0.910 V versus the reversible hydrogen electrode (RHE) in 0.5 m H 2 SO 4 and 0.1 m KOH, respectively, along with respectable durability. Such performance surpasses that of most reported non-PGM ORR catalysts. Density functional theory calculations suggest that the relieved passivation effect of OH* on Fe-N 4 /C structure leads to its superior ORR activity to Pt/C in alkaline solution. The work demonstrates a novel strategy for developing high-performance non-PGM ORR electrocatalysts with atomically dispersed and stable M-N x coordination sites in both acidic and alkaline media.

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confidence: 96%

Atomically Dispersed Fe‐N_x/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy

Miao

Wang

Tsai

et al. 2018

Advanced Energy Materials

233

114

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“…The M–N–C materials are usually recognized as single‐atom catalysts (SACs), since isolated N‐bonded metals atoms are embedded in carbons. It has been reported previously that Fe–N–C and Co–N–C catalysts can exhibit comparable ORR activity to the commercial platinum‐supported carbon (Pt/C) catalyst in alkaline electrolytes . The remarkable ORR performance is generally resulted from the active N‐coupled metal centers, in which the N‐coordination tunes the electronic structure of metal atoms and thus modifies proper interaction with oxygen molecules adsorption as well as dissociation .…”

Section: Methodsmentioning

confidence: 99%

N,P Co‐Coordinated Manganese Atoms in Mesoporous Carbon for Electrochemical Oxygen Reduction

Zhu

Amal

2019

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The increasing interest in fuel cell technology encourages the development of efficient and low‐cost electrocatalysts to replace the Pt based materials for catalyzing the cathodic oxygen reduction reaction (ORR). In the present work, a nitrogen and phosphorus co‐coordinated manganese atom embedded mesoporous carbon composite (MnNPC‐900) is successfully prepared via a polymerization of o‐phenylenediamine followed by calcination at 900 °C. The MnNPC‐900 composite shows a high ORR activity in alkaline media, offering an onset potential of 0.97 V, and a half‐wave potential of 0.84 V (both vs reversible hydrogen electrode) with a loading of 0.4 mg cm−2. This performance not only exceeds its phosphorus‐free counterpart (MnNC‐900), but also is comparable to the Pt/C catalyst under identical measuring conditions. The significantly enhanced ORR performance of MnNPC‐900 can be ascribed to: i) the introduction of phosphorus assists the generation of mesopores during the pyrolysis and endows the MnNPC‐900 composite with large surface area and pore volume, thus facilitating the mass transfer process and increases the number of exposed active sites. ii) The formation of N,P co‐coordinated atomic‐scale Mn sites (MnNxPy), which modifies the electronic configuration of the Mn atoms and thereby boosts the ORR catalytic activity.

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“…g) Room‐temperature 57 Fe Mössbauer spectrum of Fe‐N‐C‐950; h) ORR polarization plots in O 2 ‐saturated 0.1 m HClO 4 (5 mV s −1 , 1600 rpm). Reproduced with permission . Copyright 2018, American Chemical Society.…”

Section: Applications Of Mof‐derived Carbon‐supported Sacsmentioning

confidence: 99%

“…Significant particle agglomeration would occur when the size is reduced to 20 nm, leading to decrease of the activity. To make a comprehensive understanding of catalytic site structure and the ORR mechanism, Xiao et al performed 57 Fe Mössbauer, XAS for Fe L‐edge and in situ XANES studies . In the Fe‐N‐C catalysts, a high‐spin O x ‐Fe 3+ ‐N 4 configuration was considered to be active in the ORR, with an onset potential of 0.92 V (Figure g,h).…”

Section: Applications Of Mof‐derived Carbon‐supported Sacsmentioning

confidence: 99%

Recent Advances for MOF‐Derived Carbon‐Supported Single‐Atom Catalysts

et al. 2019

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Single‐atom catalysts have drawn considerable attention because of their unique catalytic properties. However, the high surface energy of single atoms restricts their fabrication and creates significant challenges for further developments. In order to overcome this problem, metal organic framework (MOF)‐derived carbon materials can be served as ideal supports to anchor atomically dispersed metal atoms, due to their tunable particle size and shape features, by providing high surface area, porosity, thermal, and chemical stability. This review highlights the recent advances in i) different types of construction strategies for MOF‐derived carbon‐supported single‐atom catalysts, and ii) the catalytic applications of these MOF‐derived carbon‐supported single‐atom catalysts. Further, this review offers a valuable insight into the current challenges and future opportunities for MOF‐derived carbon‐supported single‐atom catalysts.

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Microporous Framework Induced Synthesis of Single-Atom Dispersed Fe-N-C Acidic ORR Catalyst and Its in Situ Reduced Fe-N₄ Active Site Identification Revealed by X-ray Absorption Spectroscopy

Cited by 473 publications

References 60 publications

Atomically Dispersed Fe‐N_x/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy

Atomically Dispersed Fe‐N_x/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy

N,P Co‐Coordinated Manganese Atoms in Mesoporous Carbon for Electrochemical Oxygen Reduction

Recent Advances for MOF‐Derived Carbon‐Supported Single‐Atom Catalysts

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Microporous Framework Induced Synthesis of Single-Atom Dispersed Fe-N-C Acidic ORR Catalyst and Its in Situ Reduced Fe-N4 Active Site Identification Revealed by X-ray Absorption Spectroscopy

Cited by 473 publications

References 60 publications

Atomically Dispersed Fe‐Nx/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy

Atomically Dispersed Fe‐Nx/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy

N,P Co‐Coordinated Manganese Atoms in Mesoporous Carbon for Electrochemical Oxygen Reduction

Recent Advances for MOF‐Derived Carbon‐Supported Single‐Atom Catalysts

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Microporous Framework Induced Synthesis of Single-Atom Dispersed Fe-N-C Acidic ORR Catalyst and Its in Situ Reduced Fe-N₄ Active Site Identification Revealed by X-ray Absorption Spectroscopy

Atomically Dispersed Fe‐N_x/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy

Atomically Dispersed Fe‐N_x/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy