Surface Diels–Alder adducts on multilayer graphene for the generation of edge-enriched single-atom FeN<sub>4</sub> sites for ORR and OER electrocatalysis

Amaro-Gahete, Juan; Salatti-Dorado, José Ángel; Benítez, Almudena; Esquivel, Dolores; García-Caballero, Valentin; López‐Haro, Miguel; Delgado, Juan J.; Giner‐Casares, Juan J.; Romero–Salguero, Francisco J.

doi:10.1039/d2se00004k

Cited by 7 publications

(1 citation statement)

References 117 publications

(135 reference statements)

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“…Among the different types of SACs, carbon-based SACs with an individual transition metal center have been widely explored for electrocatalysis. − Notably, the Fe-embedded N-doped graphene (Fe–N–C) is the most representative case among the carbon-based SACs, which have been studied as promising electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. − However, highly diverse FeN x sites and spin states, as well as coordinated ligands, are introduced into the Fe–N–C depending on the synthetic conditions, which makes the identification of active site very challenging and limits the mechanistic understanding of the Fe–N–C catalyst. − Thus, an in-depth understanding of the electrocatalytic behavior of Fe–N–C is quite necessary for further improvement of the catalytic performance and theory-guided design of catalysts.…”

Section: Introductionmentioning

confidence: 99%

Substantial Impact of Spin State Evolution in OER/ORR Catalyzed by Fe–N–C

Yu,

Li,

Kan

et al. 2024

ACS Catal.

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The Fe-embedded N-doped graphene (Fe−N−C) is the most representative single atom catalyst (SAC) that has shown great potentiality in electrocatalysis, such as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the active moiety of Fe−N−C is still elusive due to contradictory experimental results. Moreover, early simulations mainly focus on the thermodynamic potential of adsorbates, while the effect of spin multiplicity receives little attention. To explore the role of spin multiplicity in electrocatalysis, we employ the constant-potential density functional theory (DFT) to systematically study the structural evolution of the high-spin (HS) and intermediate-spin (IS) FeN 4 site (marked by FeN 4 HS/IS ) in OER and ORR processes. With the consideration of spin multiplicity, our simulation shows spontaneous oxidation from Fe(II)N 4 IS to Fe(III)N 4 HS at potential U = 0.4 V versus SHE. Further simulation indicates that the FeN 4 IS site undergoes a sequential adsorption of *OH and *OOH along with U increase, which leads to the spin state transition from IS to HS. According to the constant-potential free energy analysis, the FeN 4 HS *OOH is confirmed to be the practical active centers of OER, while the FeN 4 HS *OH and FeN 4 IS are assigned to the active center of ORR in low and high overpotentials. The predicted ORR activity of FeN 4 HS *OH agrees with the in situ X-ray absorption near-edge spectroscopy (XANES) and 57 Fe Mossbauer spectroscopy measurement by Xiao et al. [Microporous Framework Induced Synthesis of Single-Atom Dispersed Fe-NC Acidic ORR Catalyst and its In Situ Reduced Fe-N 4 Active Site Identification Revealed by X-Ray Absorption Spectroscopy. ACS Catal. 2018, 8, 2824−2832]. Based on the geometry and orbital analysis, the bond length of Fe−N and coordination number of Fe center are found to have a significant impact on the d orbital splitting energy and thus induce the turnover of HS/IS stability in the OER/ORR intermediates. Our study brings comprehensive insights into the evolution of coordination and spin state in Fe−N−C, which reveals the significance of spin multiplicity in electrocatalysis and benefits further theoretical design of SACs from the perspective of spin effects.

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Section: Introductionmentioning

confidence: 99%

Substantial Impact of Spin State Evolution in OER/ORR Catalyzed by Fe–N–C

Yu,

Li,

Kan

et al. 2024

ACS Catal.

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Sulfonated Graphene‐Based Materials as Heterogeneous Acid Catalysts for Solketal Synthesis by Acetalization of Glycerol

Gil‐Gavilán,

Amaro‐Gahete,

Rojas‐Luna

et al. 2024

ChemCatChem

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Acid catalysis plays a pivotal role in the industrial landscape due to its contributions to various chemical processes in numerous sectors, including petrochemicals, polymers, food processing, and biodiesel production, among others. Sulfonated graphenes hold notable relevance as heterogeneous acid catalysts due to their unique combination of graphene's structural properties and the introduction of sulfonic groups as catalytic acid sites. Herein, we report the preparation of three sulfonated graphene‐based materials ‐ sulfonated reduced graphene oxide (rGO‐SO3H), chlorosulfonated reduced graphene oxide (rGO‐HSO3Cl) and sulfonated graphene oxide (GO‐SO3H)‐ by different synthetic approaches. Physicochemical, textural, morphological, and acidic properties were characterized by different instrumental techniques. Innovatively, these materials have been evaluated as heterogenenous acid catalysts in the solketal synthesis by acetalization of glycerol, which is considered an interesting building block to produce added‐value products. The density of acidic active sites and hydrophobicity were found to be conditioning parameters of the resulting catalytic activity in terms of conversion and selectivity. The best catalytic performance was obtained by rGO‐SO3H, reaching the maximum conversion towards solketal in 15 minutes under mild reaction conditions. The reusability and stability of all materials were also examined after three consecutive acetalization reactions with only a slight loss of catalytic activity.

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Electron transfer-mediated peroxymonosulfate activation through monoatomic Fe–pyridinic N4 moiety in biochar-based catalyst for electron-rich pollutants degradation in groundwater

Zhou,

Wang,

Dong

et al. 2024

Chemical Engineering Journal

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Surface Diels–Alder adducts on multilayer graphene for the generation of edge-enriched single-atom FeN₄ sites for ORR and OER electrocatalysis

Abstract: The assembly of atomically dispersed iron-nitrogen (FeN4) sites into graphitic structures is a promising approach for sustainable production of bifunctional electrocatalysts for oxygen electroreduction (ORR) and oxygen evolution (OER) reactions....

Cited by 7 publications

References 117 publications

Substantial Impact of Spin State Evolution in OER/ORR Catalyzed by Fe–N–C

Substantial Impact of Spin State Evolution in OER/ORR Catalyzed by Fe–N–C

Sulfonated Graphene‐Based Materials as Heterogeneous Acid Catalysts for Solketal Synthesis by Acetalization of Glycerol

Electron transfer-mediated peroxymonosulfate activation through monoatomic Fe–pyridinic N4 moiety in biochar-based catalyst for electron-rich pollutants degradation in groundwater

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Surface Diels–Alder adducts on multilayer graphene for the generation of edge-enriched single-atom FeN4 sites for ORR and OER electrocatalysis

Abstract: The assembly of atomically dispersed iron-nitrogen (FeN4) sites into graphitic structures is a promising approach for sustainable production of bifunctional electrocatalysts for oxygen electroreduction (ORR) and oxygen evolution (OER) reactions....

Cited by 7 publications

References 117 publications

Substantial Impact of Spin State Evolution in OER/ORR Catalyzed by Fe–N–C

Substantial Impact of Spin State Evolution in OER/ORR Catalyzed by Fe–N–C

Sulfonated Graphene‐Based Materials as Heterogeneous Acid Catalysts for Solketal Synthesis by Acetalization of Glycerol

Electron transfer-mediated peroxymonosulfate activation through monoatomic Fe–pyridinic N4 moiety in biochar-based catalyst for electron-rich pollutants degradation in groundwater

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Surface Diels–Alder adducts on multilayer graphene for the generation of edge-enriched single-atom FeN₄ sites for ORR and OER electrocatalysis