High-purity pyrrole-type FeN<sub>4</sub> sites as a superior oxygen reduction electrocatalyst

Zhang, Nan; Zhou, Tianshou; Chen, Minglong; Hu, Feng; Yuan, Ruilin; Zhong, Cheng’an; Yan, Wensheng; Tian, Yangchao; Wu, Xiaojun; Chu, Wangsheng; Wu, Changzheng; Xie, Yi

doi:10.1039/c9ee03027a

Cited by 373 publications

(299 citation statements)

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“…[ 14 ] Among the various MN 4 coordination catalysts, FeN 4 is reported to exhibit the highest ORR activity, whose intrinsic activity is reported as high as 6.89 mA m −2 . [ 15a ] The current explanation of the promising ORR activity on FeN 4 mainly focus on the viewpoint of electronic structures or free energy diagram computed through DFT calculations. For example, Wu and co‐workers have computed the density of states (DOS) of FeN 4 with and without a 2% FeN bond contraction ( Figure a) and attributed the better activity of FeN 4 with FeN bond contraction to the positive shifting of the 3d orbitals of central Fe, which facilitates oxygen adsorption on FeN 4 sites (Figure 3b).…”

Section: Examples Of Spin‐electrocatalysis In Oer and Orrmentioning

confidence: 99%

“…For example, Wu and co‐workers have computed the density of states (DOS) of FeN 4 with and without a 2% FeN bond contraction ( Figure a) and attributed the better activity of FeN 4 with FeN bond contraction to the positive shifting of the 3d orbitals of central Fe, which facilitates oxygen adsorption on FeN 4 sites (Figure 3b). [ 15b ] Xie and co‐workers calculated the free energy diagrams of ORR on pyrrole‐type and pyridine‐type FeN 4 . They found that pyrrole‐type FeN 4 exhibits lower thermodynamic overpotential (0.35 eV) from the initial state (O 2 ) to the final state (H 2 O) than that of pyridine‐type (0.67 eV) in a typical 4e − pathway.…”

Section: Examples Of Spin‐electrocatalysis In Oer and Orrmentioning

confidence: 99%

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Spin‐Related Electron Transfer and Orbital Interactions in Oxygen Electrocatalysis

et al. 2020

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renewable and ecofriendly energy technologies, such as fuel cells and water splitting. Currently, theoretical insights of oxygen electrocatalysis mainly focus on the thermodynamic features of the adsorption/desorption of reactants and intermediates. Besides the thermodynamic features, the electron transfer between the adsorbed reactants/intermediates and the active sites, and the charge transport within the catalysts during the electrocatalysis, are also a crucial factor influencing the reaction kinetics. That is, a comprehensible understanding of oxygen electrocatalysis should consider both the orbital interactions and the electron transfer behavior. In the domain of oxygen electrocatalysis (at room temperature in water), the electron transfer exhibits highly spin-related character because the ground state of O 2 mole cule is a triplet state (↑OO↑) (Figure 1). That is why O 2 is paramagnetic. Therefore, either from H 2 O/OH − to O 2 (oxygen evolution reaction, OER) or from O 2 to H 2 O/OH − (oxygen reduction reaction, ORR), the involvement of the triplet O 2 requires spin-related electron transfer along these oxygen reactions, which plays a considerable role in the reaction kinetics. The aspect of spin-related electron transfer has been unintentionally neglected and only a few pioneer works have noticed and emphasized its role. An early attempt can be traced back Oxygen evolution and reduction reactions play a critical role in determining the efficiency of the water cycling (H 2 O ⇔ H 2 + 1 2 O 2), in which the hydrogen serves as the energy carrier. That calls for a comprehensive understanding of oxygen electrocatalysis for efficient catalyst design. Current opinions on oxygen electrocatalysis have been focused on the thermodynamics of the reactant/intermediate adsorption on the catalysts. Because the oxygen molecule is paramagnetic, its production from or its reduction to diamagnetic hydroxide/water involves spin-related electron transfer. Both electron transfer and orbital interactions between the catalyst and the reactant/intermediate show spin-dependent character, making the reaction kinetics and thermodynamics sensitive to the spin configurations. Herein, a brief introduction on the spintronic explanation of the catalytic phenomena on oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is given. The local spin configurations and orbital interactions in the benchmark transition-metalbased catalysts for OER and ORR are analyzed as examples. To further understand the spintronic oxygen electrocatalysis and to develop more efficient spintronic catalysts, the challenges are summarized and future opportunities proposed. Spin electrocatalysis may emerge as an important topic in the near future and help integrate a comprehensive understanding of oxygen electrocatalysis.

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Section: Examples Of Spin‐electrocatalysis In Oer and Orrmentioning

confidence: 99%

Section: Examples Of Spin‐electrocatalysis In Oer and Orrmentioning

confidence: 99%

Spin‐Related Electron Transfer and Orbital Interactions in Oxygen Electrocatalysis

et al. 2020

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“…As shown in Figure 5(c), Fe-N-C catalysts were reported from Fe-dual pyridine coordination complexes, which exhibit highly efficient oxygen reduction [132]. Our group [133] revealed that, compared to pyridinic and graphitic N, a high-purity pyrrole-type FeN 4 electrocatalysts regulated the atomic and electronic structure of active sites ( Figure 5(d)), which greatly enhanced high intrinsic catalytic activity. Based on the X-ray absorption near edge structure (XANES) analysis and fitting results, the detailed arrangement of carbon in Fe-N x -C moieties was revealed as FeN 4 C 12 .…”

Section: Atomic Coordination Configurationmentioning

confidence: 84%

Local structure engineering for active sites in fuel cell electrocatalysts

et al. 2020

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In this review, we surveyed the significance of local structure engineering on electrocatalysts and electrodes for the performance of oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Both on precious metal catalysts (PMC) and non-precious metal catalysts (NPMC), the main methods to modulate local structure of active sites have been summarized. By change of atomic coordination, modulation of bonding distortion and synergy effect from hierarchical structure, local structure engineering has influence on the intrinsic activity and stability of electrocatalysts. Moreover, we emphasized the intimate correlation between lyophobicity of electrocatalysts and membrane electrodes by local structure engineering. Our review aimed to inspire the exploration of advanced electrocatalysts and mechanism study for PEMFCs based on local structure engineering. local structure engineering, proton exchange membrane fuel cells, oxygen reduction reaction, active sites

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“…[57] Highpurity pyrrole-type Fe-N 4 motifs were achieved via topochemical transformation from pyridinic N to pyrrolic N, with the assistance of the NH 3 -etching approach (Figure 3c). [58] The N-K edge X-ray absorption near edge structure (XANES) spectra indicate the presence of Fe-pyrrolic N coordination structure without pyridinic-N coordinated Fe sites in as-prepared catalysts. The pyrrole-type FeN 4 sites are preferable for oxygen adsorption and exhibit a better kinetic activity for ORR than these of other references in acidic electrolytes (Figure 3d), as supported by experimental and DFT results.…”

Section: Heteroatom Dopingmentioning

confidence: 99%

Section: Heteroatom Dopingmentioning

confidence: 99%

Structural Regulation and Support Coupling Effect of Single‐Atom Catalysts for Heterogeneous Catalysis

Liu

Ding

et al. 2020

Advanced Energy Materials

210

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Single atom catalysts (SACs) that integrate the merits of homogeneous and heterogeneous catalysts have been attracting considerable attention in recent years. The individual metal atoms of SACs can be stabilized on supports through various unsaturated chemical sites or space confinement for achieving the maximized atom utilization efficiency. Aside from the development of strategies for preparing high loading and high purity SACs, another key challenge in this field is precisely manipulating the geometric and electronic structure of catalytically active single metal sites, thus rendering the catalysts exceptionally reactive, selective, and stabile compared to their bulk counterparts. This review summarizes recent advancements in SACs for heterogeneous catalysis from the perspective of local structural regulation and the synergistic coupling effect between metal species and supports. Special emphasis is placed on the elucidation of the catalytic structure‐performance relationship in terms of coordination environment, valence state and metal‐support interactions by advanced characterization and theoretical studies. Select in situ or operando characterization techniques for tracking the SACs’ structure evolution under realistic conditions are highlighted. Finally, the challenges and opportunities are discussed to offer insight into the rational design of more intriguing SACs with high activity and distinct chemoselectivity.

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High-purity pyrrole-type FeN₄ sites as a superior oxygen reduction electrocatalyst

Abstract: High-purity pyrrole-type FeN4 sites have been developed as a superior oxygen reduction catalyst for proton exchange membrane fuel cells.

Cited by 373 publications

References 42 publications

Spin‐Related Electron Transfer and Orbital Interactions in Oxygen Electrocatalysis

Spin‐Related Electron Transfer and Orbital Interactions in Oxygen Electrocatalysis

Local structure engineering for active sites in fuel cell electrocatalysts

Structural Regulation and Support Coupling Effect of Single‐Atom Catalysts for Heterogeneous Catalysis

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High-purity pyrrole-type FeN4 sites as a superior oxygen reduction electrocatalyst

Abstract: High-purity pyrrole-type FeN4 sites have been developed as a superior oxygen reduction catalyst for proton exchange membrane fuel cells.

Cited by 373 publications

References 42 publications

Spin‐Related Electron Transfer and Orbital Interactions in Oxygen Electrocatalysis

Spin‐Related Electron Transfer and Orbital Interactions in Oxygen Electrocatalysis

Local structure engineering for active sites in fuel cell electrocatalysts

Structural Regulation and Support Coupling Effect of Single‐Atom Catalysts for Heterogeneous Catalysis

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High-purity pyrrole-type FeN₄ sites as a superior oxygen reduction electrocatalyst