Bonding and Electronic Structure of Phosphides, Arsenides, and Antimonides by X-Ray Photoelectron and Absorption Spectroscopies

Grosvenor, Andrew P.; Cavell, Ronald G.; Mar, Arthur

doi:10.1007/978-3-642-01562-5_2

Cited by 7 publications

(5 citation statements)

References 99 publications

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“…This value is higher compared to that of the P in bimetallic phosphides, indicating that the oxidation state of the P in all of the bimetallic phosphides in this work is slightly anionic . The measurements agree with other works that have observed lower binding energies in phosphides in comparison to those in elemental P due to the charge transfer between the metals and P atoms …”

Section: Resultssupporting

confidence: 88%

“…55 The measurements agree with other works that have observed lower binding energies in phosphides in comparison to those in elemental P due to the charge transfer between the metals and P atoms. 56 The Mo 3d region was deconvoluted based on the method described in the Experimental Section. The Mo 3d 5/2 binding energy shifts are 227.74, 227.68, and 227.62 eV for FeMoP, CoMoP, and NiMoP, respectively, while the binding energy shift of Mo 3d 5/2 in RuMoP is 228.58 eV (Figure 3b).…”

Section: Resultsmentioning

confidence: 99%

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Periodic Trends from Metal Substitution in Bimetallic Mo-Based Phosphides for Hydrodeoxygenation and Hydrogenation Reactions

Bonita

Hicks

2018

J. Phys. Chem. C

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Bimetallic phosphides are promising materials for biomass valorization, yet many metal combinations are understudied as catalysts and require further analysis to realize their superior properties. Herein, we provide the synthesis, characterization, and catalytic performance of a variety of period 4 and 5 solid solutions of molybdenum-based bimetallic phosphides (MMoP, M = Fe, Co, Ni, Ru). From the results, the charge sharing between the metals and phosphorus control the relative oxidation of Mo and reduction of P in the lattice, which were both indirectly observed in binding energy shifts in X-ray photoelectron spectroscopy (XPS) and absorption energy shifts in X-ray absorption near-edge spectroscopy (XANES). For MMoP (M = Fe, Co, Ni), the more oxidized the Mo in the bimetallic phosphide, the higher the selectivity to benzene from phenol via direct deoxygenation at 400 °C and 750 psig. This phenomenon was observed in the bimetallic materials synthesized across period 4, where aromatic selectivity and degree of Mo oxidation both decreased in the following order FeMoP ≫ CoMoP > NiMoP. Alternatively, in the case of MMoP (M = Fe, Ru), the P in RuMoP is more oxidized compared to that in FeMoP, and the selectivity toward the hydrogenation pathway increased due to the interaction between the aromatic rings and the P species on the surface. For RuMoP and NiMoP, cyclohexanol was selectively produced from phenol with >99% selectivity when the reaction temperature was lowered to 125 °C at 750 psig, whereas FeMoP and CoMoP were not active under these conditions. Last, complete deoxygenation of phenol to benzene, cyclohexane, and cyclohexene was accomplished using mixtures of RuMoP and FeMoP in flow and batch experiments. These results highlight the versatility and wide applicability of transition metal phosphides for biomass conversions.

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Periodic Trends from Metal Substitution in Bimetallic Mo-Based Phosphides for Hydrodeoxygenation and Hydrogenation Reactions

Bonita

Hicks

2018

J. Phys. Chem. C

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“…This notion is supported by the lowering of the white line intensity of the high nZVI dose sample compared to the FeAsS and elemental arsenic data. A similar trend was noted in the data from Grosvenor et al showing that an increased anionic character of As with decreased concentration of P in FeAs x P y compounds corresponds to a reduction of the white line in the arsenic K-edge XANES spectra. Since the valence state of arsenic in FeAsS is −1, we propose the valence state for arsenic in the high nZVI dose sample to be −1 or lower.…”

Section: Resultssupporting

confidence: 86%

“…Oxidized species (As(V)) was observed to be predominantly at the outer surface of the oxide shell, while reduced species were enriched in a subsurface layer close to the Fe(0) core. In principle, the reduced arsenic may segregate as a separate phase or interact with Fe(0) to form iron–arsenic solid solutions or iron arsenide minerals such as loellingite. − Identifying the nature of the embedded arsenic requires techniques that are capable of probing the core or bulk of the nanoparticles and generating data related to the local bonding environment of arsenic. Although XPS is a powerful tool to investigate the chemical state and near-surface depth distribution of arsenic in nZVI, it is commonly conducted in ultrahigh vacuum and has a probing depth limited to ∼10 nm beneath the sample surface.…”

Section: Introductionmentioning

confidence: 99%

Intraparticle Reduction of Arsenite (As(III)) by Nanoscale Zerovalent Iron (nZVI) Investigated with In Situ X-ray Absorption Spectroscopy

Yan

Vasić

Frenkel

et al. 2012

Environ. Sci. Technol.

133

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While a high efficiency of contaminant removal by nanoscale zerovalent iron (nZVI) has often been reported for several contaminants of great concern, including aqueous arsenic species, the transformations and translocation of contaminants at and within the nanoparticles are not clearly understood. By analysis using in situ time-dependent X-ray absorption spectroscopy (XAS) of the arsenic core level for nZVI in anoxic As(III) solutions, we have observed that As(III) species underwent two stages of transformation upon adsorption at the nZVI surface. The first stage corresponds to breaking of As-O bonds at the particle surface, and the second stage involves further reduction and diffusion of arsenic across the thin oxide layer enclosing the nanoparticles, which results in arsenic forming an intermetallic phase with the Fe(0) core. Extended X-ray absorption fine-structure (EXAFS) data from experiments conducted at different iron/arsenic ratios indicate that the reduced arsenic species tend to be enriched at the surface of the Fe(0) core region and had limited mobility into the interior of the metal core within the experimental time frame (up to 22 h). Therefore, there was an accumulation of partially reduced arsenic at the Fe(0)/oxide interface when a relatively large arsenic content was present in the solid phase. These results illuminate the role of intraparticle diffusion and reduction in affecting the chemical state and spatial distribution of arsenic in nZVI materials.

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“…Transition metal phosphides are an interesting class of materials and worth investigating on the nanoscale because of their wide scope of properties and applications . Among these, iron phosphides and their ternary phases have been targeted for their magnetic characteristics, which include ferromagnetism, magneto-resistance, and magneto-caloric effects. , However, iron phosphides exist in a wide range of stoichiometries including Fe 3 P, Fe 2 P, FeP, FeP 2 , and FeP 4 , and the properties depend sensitively on their physical and electronic structure. − Thus, Fe 3 P and Fe 2 P are ferromagnetic, FeP is metamagnetic, and FeP 2 and FeP 4 are diamagnetic semiconductors. These properties are expected to vary with size and shape when prepared on the nanoscale, opening up new avenues of investigation and potential applications.…”

mentioning

confidence: 99%

Control of Phase in Phosphide Nanoparticles Produced by Metal Nanoparticle Transformation: Fe₂P and FeP

et al. 2009

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The transformation of Fe nanoparticles by trioctylphosphine (TOP) to phase-pure samples of either Fe(2)P or FeP is reported. Fe nanoparticles were synthesized by the decomposition of Fe(CO)(5) in a mixture of octadecene and oleylamine at 200 degrees C and were subsequently reacted with TOP at temperatures in the region of 350-385 degrees C to yield iron phosphide nanoparticles. Shorter reaction times favored an iron-rich product (Fe(2)P), and longer reaction times favored a phosphorus-rich product (FeP). The reaction temperature was also a crucial factor in determining the phase of the final product, with higher temperatures favoring FeP and lower temperatures Fe(2)P. We also observe the formation of hollow structures in both FeP spherical nanoparticles and Fe(2)P nanorods, which can be attributed to the nanoscale Kirkendall effect. Magnetic measurements conducted on phase-pure samples suggest that approximately 8 x 70 nm Fe(2)P rods are ferromagnetic with a Curie temperature between 215 and 220 K and exhibit a blocking temperature of 179 K, whereas FeP is metamagnetic with a Neel temperature of approximately 120 K. These data agree with the inherent properties of bulk-phase samples and attest to the phase purity that can be achieved by this method.

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Bonding and Electronic Structure of Phosphides, Arsenides, and Antimonides by X-Ray Photoelectron and Absorption Spectroscopies

Cited by 7 publications

References 99 publications

Periodic Trends from Metal Substitution in Bimetallic Mo-Based Phosphides for Hydrodeoxygenation and Hydrogenation Reactions

Periodic Trends from Metal Substitution in Bimetallic Mo-Based Phosphides for Hydrodeoxygenation and Hydrogenation Reactions

Intraparticle Reduction of Arsenite (As(III)) by Nanoscale Zerovalent Iron (nZVI) Investigated with In Situ X-ray Absorption Spectroscopy

Control of Phase in Phosphide Nanoparticles Produced by Metal Nanoparticle Transformation: Fe₂P and FeP

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Bonding and Electronic Structure of Phosphides, Arsenides, and Antimonides by X-Ray Photoelectron and Absorption Spectroscopies

Cited by 7 publications

References 99 publications

Periodic Trends from Metal Substitution in Bimetallic Mo-Based Phosphides for Hydrodeoxygenation and Hydrogenation Reactions

Periodic Trends from Metal Substitution in Bimetallic Mo-Based Phosphides for Hydrodeoxygenation and Hydrogenation Reactions

Intraparticle Reduction of Arsenite (As(III)) by Nanoscale Zerovalent Iron (nZVI) Investigated with In Situ X-ray Absorption Spectroscopy

Control of Phase in Phosphide Nanoparticles Produced by Metal Nanoparticle Transformation: Fe2P and FeP

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Control of Phase in Phosphide Nanoparticles Produced by Metal Nanoparticle Transformation: Fe₂P and FeP