Mononuclear Fe in N-doped carbon: computational elucidation of active sites for electrochemical oxygen reduction and oxygen evolution reactions

Shang, Rui; Steinmann, Stephan N.; Xu, Bin; Sautet, Philippe

doi:10.1039/c9cy01935a

Cited by 38 publications

(45 citation statements)

References 56 publications

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“…Spin density plots are sometimes used in the FeNC literature to characterize and discuss the electronic structures. [ 131 ] In contrast to the indistinguishable electron densities, the spin density plots do show some discernible differences (Figure 6B,D). In the “initial” incorrect electronic structure description where one iron α d‐orbital was erroneously unoccupied, β spin density (yellow) is seen on the nitrogen donor atoms (Figure 6B).…”

Section: Resultsmentioning

confidence: 91%

Calibration of computational Mössbauer spectroscopy to unravel active sites in FeNC catalysts for the oxygen reduction reaction

Gallenkamp

Kramm

Proppe

et al. 2020

Int J of Quantum Chemistry

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Single-atom catalysts with iron ions in the active site, known as FeNC catalysts, show high activity for the oxygen reduction reaction and hence hold promise for access to low-cost fuel cells. Because of the amorphous, multiphase structure of the FeNC catalysts, the iron environment and its electronic structure are poorly understood. While it is widely accepted that the catalytically active site contains an iron ion ligated by several nitrogen donors embedded in a graphene-like plane, the exact structural details, such as the presence or nature of axial ligands, are unknown. Computational chemistry in combination with Mössbauer spectroscopy can help unravel the geometric and electronic structures of the active sites. As a first step toward this goal, we present a calibration of computational Mössbauer spectroscopy for FeN 4-like environments. The uncertainty of both the isomer shift and the quadrupole splitting prediction is determined, from which trust regions for the Mössbauer parameter predictions of computational FeNC models are derived. We find that TPSSh, B3LYP, and PBE0 perform equally well; the trust regions with B3LYP are 0.13 mm s −1 for the isomer shift and 0.36 mm s −1 for the quadrupole splitting. The calibration data is made publicly available in an interactive notebook that provides predicted Mössbauer parameters with individual uncertainty estimates from computed contact densities and quadrupole splitting values. We show that a differentiation of common FeNC Mössbauer signals by a separate analysis of isomer shift and quadrupole splitting will most likely be insufficient, whereas their simultaneous evaluation will allow the assignment to adequate computational FeNC models.

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Section: Resultsmentioning

confidence: 91%

Calibration of computational Mössbauer spectroscopy to unravel active sites in FeNC catalysts for the oxygen reduction reaction

Gallenkamp

Kramm

Proppe

et al. 2020

Int J of Quantum Chemistry

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“…A similar configuration has also been identified and regarded as a possible active site for the CO 2 RR [56] and other electrocatalytic reactions. [85] Figure 7. a) CO faradaic efficiency of different-sized Fe-N-C. b) Correlation between the variation of Fe doping and its corresponding catalytic performance as parameterized by the CO partial current density.…”

Section: The Activity Of Different Fen X Configurationmentioning

confidence: 99%

Carbon‐Supported Single Metal Site Catalysts for Electrochemical CO₂ Reduction to CO and Beyond

Zhu

Yang

Peng

et al. 2021

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The electrochemical CO 2 reduction reaction (CO 2 RR) is a promising strategy to achieve electrical-to-chemical energy storage while closing the global carbon cycle. The carbon-supported single-atom catalysts (SACs) have great potential for electrochemical CO 2 RR due to their high efficiency and low cost. The metal centers' performance is related to the local coordination environment and the long-range electronic intercalation from the carbon substrates. This review summarizes the recent progress on the synthesis of carbon-supported SACs and their application toward electrocatalytic CO 2 reduction to CO and other C 1 and C 2 products. Several SACs are involved, including MN x catalysts, heterogeneous molecular catalysts, and the covalent organic framework (COF) based SACs. The controllable synthesis methods for anchoring single-atom sites on different carbon supports are introduced, focusing on the influence that precursors and synthetic conditions have on the final structure of SACs. For the CO 2 RR performance, the intrinsic activity difference of various metal centers and the corresponding activity enhancement strategies via the modulation of the metal centers' electronic structure are systematically summarized, which may help promote the rational design of active and selective SACs for CO 2 reduction to CO and beyond.

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“…In our approach, the electrode and adsorbates, as well as the surface charge which tunes the electrochemical potential are described via DFT while the electrolyte and solvent are represented by the solution of the linearized Poisson-Boltzmann (PB) equation. 50,51 Previously, we have successfully applied this approach not only to the characterization of the electrochemical interface, 52,53 but also to the elucidation of reaction mechanisms at electrified interfaces such as the oxygen evolution reaction on CoOOH 54 or on iron doped graphenes 55 and even for the electrochemical promotion of catalysis, 56,57 demonstrating its great versatility.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the Active Sites at the MoS₂/H₂O Interface via Grand-Canonical DFT: The Role of Water Dissociation

Abidi

Bonduelle‐Skrzypczak

Steinmann

2020

ACS Appl. Mater. Interfaces

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MoS 2 is a promising low-cost catalyst for the hydrogen evolution reaction (HER). However, the nature of the active sites remains debated. By taking the electrochemical potential explicitly into account using grand-canonical density functional theory (DFT) in combination with the linearized Poisson-Boltzmann equation, we herein revisit the active sites of 2H-MoS 2. In addition to the well-known catalytically active edge sites, also specific point-defects on the otherwise inert basal plane provide highly active sites for HER. Given that HER takes place in water, we also assess the reactivity of these active sites with respect to H 2 O. The thermodynamics of proton reduction as a function of the electrochemical potential reveals that four edge sites and three basal plane defects feature thermodynamic over-potentials below 0.2 V. In contrast to current proposals, many of these active sites involve adsorbed OH. The results demonstrate that even though H 2 O and OH block "active" sites, HER can also occur on these "blocked" sites, 1 reducing protons on surface OH/H 2 O entities. As a consequence, our results revise the active sites, highlighting the so far overlooked need to take the liquid component (H 2 O) of the functional interface into account when considering the stability and activity of the various active sites.

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Mononuclear Fe in N-doped carbon: computational elucidation of active sites for electrochemical oxygen reduction and oxygen evolution reactions

Abstract: First principles simulations show that in Fe and N co-doped carbon, Fe coordination controls the activity for oxygen reduction and oxygen evolution reactions, and that including the electrostatic potential has a major influence at high potential.

Cited by 38 publications

References 56 publications

Calibration of computational Mössbauer spectroscopy to unravel active sites in FeNC catalysts for the oxygen reduction reaction

Calibration of computational Mössbauer spectroscopy to unravel active sites in FeNC catalysts for the oxygen reduction reaction

Carbon‐Supported Single Metal Site Catalysts for Electrochemical CO₂ Reduction to CO and Beyond

Revisiting the Active Sites at the MoS₂/H₂O Interface via Grand-Canonical DFT: The Role of Water Dissociation

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Mononuclear Fe in N-doped carbon: computational elucidation of active sites for electrochemical oxygen reduction and oxygen evolution reactions

Abstract: First principles simulations show that in Fe and N co-doped carbon, Fe coordination controls the activity for oxygen reduction and oxygen evolution reactions, and that including the electrostatic potential has a major influence at high potential.

Cited by 38 publications

References 56 publications

Calibration of computational Mössbauer spectroscopy to unravel active sites in FeNC catalysts for the oxygen reduction reaction

Calibration of computational Mössbauer spectroscopy to unravel active sites in FeNC catalysts for the oxygen reduction reaction

Carbon‐Supported Single Metal Site Catalysts for Electrochemical CO2 Reduction to CO and Beyond

Revisiting the Active Sites at the MoS2/H2O Interface via Grand-Canonical DFT: The Role of Water Dissociation

Contact Info

Product

Resources

About

Carbon‐Supported Single Metal Site Catalysts for Electrochemical CO₂ Reduction to CO and Beyond

Revisiting the Active Sites at the MoS₂/H₂O Interface via Grand-Canonical DFT: The Role of Water Dissociation