A self‐consistent multiple‐peak structure of the photoemission spectra of metallic Fe 2<i>p</i> as a function of film thickness

Herrera-Gómez, Alberto; Cortazar‐Martínez, Orlando; Fabian‐Jocobi, Jesus‐Fernando; Carmona-Carmona, Abraham Jorge; Raboño‐Borbolla, Joaquin‐Gerardo; Bravo-Sánchez, Mariela; Huerta-Ruelas, Jorge A.

doi:10.1002/sia.6796

Cited by 6 publications

(3 citation statements)

References 27 publications

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“…The Anderson singularity index α describes the asymmetry of the lineshape due to the probability of electron-hole pairs excitation. The decision of using the Doniach-Šunjić function convoluted with a Gaussian distribution rather than the Voigt function, often preferred for quantitative analysis 47 , is justified by the fact that we are not interested in a composition analysis of the oxidized iron clusters, but in obtaining information about the asymmetry when it is present, as in clusters spectra before the oxidation process. Doniach-Šunjić functions convoluted with a Gaussian distribution have been extensively used in literature for fitting both metallic and oxidized surfaces 48 , 49 .…”

Section: Resultsmentioning

confidence: 99%

The highest oxidation state observed in graphene-supported sub-nanometer iron oxide clusters

et al. 2023

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Size-selected iron oxide nanoclusters are outstanding candidates for technological-oriented applications due to their high efficiency-to-cost ratio. However, despite many theoretical studies, experimental works on their oxidation mechanism are still limited to gas-phase clusters. Herein we investigate the oxidation of graphene-supported size-selected Fen clusters by means of high-resolution X-ray Photoelectron Spectroscopy. We show a dependency of the core electron Fe 2p3/2 binding energy of metallic and oxidized clusters on the cluster size. Binding energies are also linked to chemical reactivity through the asymmetry parameter which is related to electron density of states at the Fermi energy. Upon oxidation, iron atoms in clusters reach the oxidation state Fe(II) and the absence of other oxidation states indicates a Fe-to-O ratio close to 1:1, in agreement with previous theoretical calculations and gas-phase experiments. Such knowledge can provide a basis for a better understanding of the behavior of iron oxide nanoclusters as supported catalysts.

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Section: Resultsmentioning

confidence: 99%

The highest oxidation state observed in graphene-supported sub-nanometer iron oxide clusters

et al. 2023

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“…The complex structure of the metallic Fe 2p core level would necessitate the presence of satellite peaks, which include plasmon features, along with the main metallic lines. [ 40 ] On the other hand, Ni 2p 3/2 core‐level component of the as‐synthesized samples can be fitted with an asymmetric metallic peak at binding energy (BE) of 852.9 eV, its satellite features, as well as Ni 2+ hydroxide multiplet and its corresponding satellites. The presence of Ni(OH) 2 implies that in the as‐synthesized nanoalloys, Ni prefers hydroxylation to oxidation in a high humidity environment.…”

Section: Resultsmentioning

confidence: 99%

Tuning Electronic Structure and Composition of FeNi Nanoalloys for Enhanced Oxygen Evolution Electrocatalysis via a General Synthesis Strategy

Wang

Nong

Gong

et al. 2022

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Electrocatalytic water splitting has recently surfaced as a promising method by transforming them into hydrogen fuel. [2] The bottleneck in the development of electrochemical water splitting technology is the oxygen evolution reaction (OER), which is the half reaction at the anode. [3] OER has very sluggish kinetics because it is a four proton-electron transfer process. [4] It is also a vital half-reaction for rechargeable metal-air batteries. [5] Therefore, efficient electrocatalysts are required to overcome the high OER overpotential. Currently, both RuO 2 and IrO 2 are regarded as the state-of-theart electrocatalysts for OER. [6][7][8] However, both of them show poor dissolution resistance under high anodic potential. [9,10] Moreover, their high price and scarcity make it vital to develop cost-effective, highly active, and durable electrocatalysts for OER. [11] Nanomaterial electrocatalysts are generally more efficient than their bulk counterparts due to larger specific surface areas and higher mass activities. Therefore, electrocatalysts with smaller size are normally desired for improved electrocatalytic performance. [12] For example, reducing the size of Cu nanoparticles can significantly increase its catalytic activity because of the increased low-coordination sites acting as active sites. [13] Likewise, size-dependent electrocatalytic activity has also been observed for Au nanoparticles. [14] However, it is still challenging Developing low-cost and efficient oxygen evolution electrocatalysts is key to decarbonization. A facile, surfactant-free, and gram-level biomass-assisted fast heating and cooling synthesis method is reported for synthesizing a series of carbon-encapsulated dense and uniform FeNi nanoalloys with a single-phase face-centered-cubic solid-solution crystalline structure and an average particle size of sub-5 nm. This method also enables precise control of both size and composition. Electrochemical measurements show that among Fe x Ni (1−x) nanoalloys, Fe 0.5 Ni 0.5 has the best performance. Density functional theory calculations support the experimental findings and reveal that the optimally positioned d-band center of O-covered Fe 0.5 Ni 0.5 renders a half-filled antibonding state, resulting in moderate binding energies of key reaction intermediates. By increasing the total metal content from 25 to 60 wt%, the 60% Fe 0.5 Ni 0.5 /40% C shows an extraordinarily low overpotential of 219 mV at 10 mA cm −2 with a small Tafel slope of 23.2 mV dec −1 for the oxygen evolution reaction, which are much lower than most other FeNi-based electrocatalysts and even the state-of-the-art RuO 2 . It also shows robust durability in an alkaline environment for at least 50 h. The gram-level fast heating and cooling synthesis method is extendable to a wide range of binary, ternary, quaternary nanoalloys, as well as quinary and denary high-entropy-alloy nanoparticles.

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“…While these latter signals may be fit with either a series of symmetric components or an asymmetric peak shape, it is often better to fit them with symmetric peak shapes. [43][44][45] Asymmetry has been an important consideration in XPS peak fitting for many years. [46][47][48] Indeed, in their classic work on polymers, Beamson and Briggs fit their peak envelopes with asymmetric peaks, where in most cases these synthetic fit components showed some degree of asymmetry.…”

Section: Introductionmentioning

confidence: 99%

A discussion of approaches for fitting asymmetric signals in X‐ray photoelectron spectroscopy (XPS), noting the importance of Voigt‐like peak shapes

Major

Avval

Patel

et al. 2021

Surface & Interface Analysis

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Although the fundamental, theoretical peak shape in X-ray photoelectron spectroscopy (XPS) is Lorentzian, some Gaussian character is observed in most XPS signals. Additional complexity in the form of asymmetry is also found in many XPS signals, which requires more advanced peak shapes than the traditional, symmetric Voigt and Gaussian-Lorentzian sum and product (pseudo-Voigt) functions. Here, we discuss the merits and disadvantages of four approaches that have been used to introduce asymmetry into XPS peak shapes: addition of a decaying exponential tail to a symmetric peak shape, the Doniach-Sunjic peak shape, the double-Lorentzian, DL, function, and

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A self‐consistent multiple‐peak structure of the photoemission spectra of metallic Fe 2p as a function of film thickness

Cited by 6 publications

References 27 publications

The highest oxidation state observed in graphene-supported sub-nanometer iron oxide clusters

The highest oxidation state observed in graphene-supported sub-nanometer iron oxide clusters

Tuning Electronic Structure and Composition of FeNi Nanoalloys for Enhanced Oxygen Evolution Electrocatalysis via a General Synthesis Strategy

A discussion of approaches for fitting asymmetric signals in X‐ray photoelectron spectroscopy (XPS), noting the importance of Voigt‐like peak shapes

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