In situ formation of hydrides and carbides in palladium catalyst: When XANES is better than EXAFS and XRD

Bugaev, Aram L.; Guda, Alexander A.; Lazzarini, Andrea; Lomachenko, Kirill A.; Groppo, Elena; Pellegrini, Riccardo; Piovano, Andrea; Emerich, Hermann; Soldatov, A. V.; Бугаев, Л. А.; Dmitriev, Vladimir; Bokhoven, Jeroen A. van; Lamberti, Carlo

doi:10.1016/j.cattod.2016.02.065

Cited by 114 publications

(134 citation statements)

References 95 publications

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“…During the refinement, we obtained the following lattice parameters: 3.907, 3.891, 3.893, and 4.01 Å for Pd-NPs NaBH 4 , Pd-NPs hydrazine , Pd-NPs ammonia,hydrazine , and Pd-NPs PEG , respectively (see Table 1 for the error bars). These lattice parameters are also close to those reported for palladium NPs and bulk palladium materials [12,17,24,30,33]. According to the analysis of peaks broadening, the mean crystallite size was 6.1 nm in the case of palladium reduced by NaBH 4 , and in case of reduction by hydrazine using ethanol and ammonia, the crystallite sizes were 8.4 nm and 13.7 nm, respectively, which is reported in Table 1 together with TEM results.…”

Section: Structure and Morphology Of Pd/sio2supporting

confidence: 85%

“…In particular, palladium is one of the best-performing metal catalysts for selective hydrogenation of alkynes [10][11][12][13][14]. Numerous studies focus on the size-and shape-dependent properties of palladium NPs [15][16][17][18][19], indicating that controlling the size and shape distribution of NPs during synthesis is an important step in designing functional materials with the required parameters for practical applications.…”

Section: Introductionmentioning

confidence: 99%

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Chemical Synthesis and Characterization of Pd/SiO2: The Effect of Chemical Reagent

Bugaev

Polyakov

Tereshchenko

et al. 2018

Metals

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The size and shape distribution of metal nanoparticles (NPs) are important parameters that need to be tuned in order to achieve desired properties of materials for practical applications. In the current work, we present the synthesis of palladium NPs supported on silica by three different methods, applying reduction by sodium borohydride, hydrazine vapors, and polyethylene glycol (PEG). The synthesized materials were characterized by X-ray diffraction, X-ray fluorescence, transmission electron microscopy, surface area and porosity measurements, and thermogravimetric analysis. Similar nanoparticle sizes with narrow size distribution centered at 8 nm were obtained after reduction by sodium borohydride and hydrazine vapors, whereas the smallest particle size of about 4.8 nm was obtained after reduction by PEG. The effect of modification of the initial palladium chloride compound by ammonium hydroxide was found to lead to the formation of larger particles with average size of 15 nm and broader size distribution. In addition, the process of the reduction of palladium by PEG at different reduction stages was monitored by UV-Vis spectroscopy. CO-stripping voltammetry showed that reduction in hydrazine and in PEG allowed the preparation of Pd NPs with high electrochemically-active surface area. Such NPs are promising materials for electrocatalysis.

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Section: Structure and Morphology Of Pd/sio2supporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Chemical Synthesis and Characterization of Pd/SiO2: The Effect of Chemical Reagent

Bugaev

Polyakov

Tereshchenko

et al. 2018

Metals

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“…Therefore Figure 3 shows XANES and EXAFS spectra of Pd foil (Goodfellow), PdO (CAS Nr. 1314-08-5, Chempur), and 1 wt.-% Pd/TiO2 catalyst in H2/H2O flow (the spectra of which correspond to β-PdHx phase [47][48][49][50]) which were further used as references for XANES and EXAFS analysis.…”

Section: Operando Xanes and Exafs Data Recorded During Direct Synthesmentioning

confidence: 99%

Revealing the Structure and Mechanism of Palladium during Direct Synthesis of Hydrogen Peroxide in Continuous Flow Using Operando Spectroscopy

Selinsek¹,

Deschner²,

Doronkin

et al. 2018

ACS Catal.

113

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The direct synthesis of H2O2 is a dream reaction in the field of selective oxidation and green chemical synthesis. However, the unknown active state of the catalyst and the lack of a defined catalytic mechanism preclude the design and optimization of suitable catalysts and reactor setups. Here direct synthesis of H2O2 over Pd-TiO2 in water was investigated in a continuous flow reactor setup utilizing undiluted oxygen and hydrogen to increase aqueous phase concentrations safely at ambient temperature and a pressure of 10 bars. In this experiment operando X-ray Absorption Spectroscopy (XAS) and online flow injection analysis for photometric quantification of H2O2 were combined to build catalyst structure-activity relationships in direct H2O2 synthesis. XAS at the Pd K absorption edge was used to observe oxidation state and local Pd structure together with H2O2 production for three reactant ratio (H2/O2) regimes: hydrogen rich (> 2), hydrogen lean (< 0.5) and balanced (0.5-2). During H2O2 production, oxygen was only found adsorbed on the surface of Pd nanoparticles and hydrogen was found dissolved in bulk palladium hydride (α-phase) indicating a reaction of surface oxygen with lattice hydrogen to form hydrogen peroxide. Under hydrogen rich conditions, formation of β-phase palladium hydride was found to coincide with zero H2O2 yield. This constitutes an operando study of direct H2O2 synthesis under elevated partial pressures of H2 and O2 in continuous flow. The results obtained will aid in rational design of future catalysts and optimization of process parameters, bringing the concept of a viable, efficient process for H2O2 synthesis one step closer to reality.

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“…To summarize, atomic-scale simulation of nanomaterial structure, guided by XAS data, is a new and rapidly developing field. The importance of and growing interest in such studies are supported by a number of recent publications devoted to this topic (15,17,19,26,(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45). The approaches described in these articles often rely on similar ideas, but their implementation varies because such combined studies are still a relatively new tool for modeling NP structure.…”

Section: Introductionmentioning

confidence: 99%

Solving the Structure and Dynamics of Metal Nanoparticles by Combining X-Ray Absorption Fine Structure Spectroscopy and Atomistic Structure Simulations

Timoshenko

Duan

Henkelman

et al. 2019

Annual Rev. Anal. Chem.

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Extended X-ray absorption fine structure (EXAFS) spectroscopy is a premiere method for analysis of the structure and structural transformation of nanoparticles. Extraction of analytical information about the three-dimensional structure and dynamics of metal–metal bonds from EXAFS spectra requires special care due to their markedly non-bulk-like character. In recent decades, significant progress has been made in the first-principles modeling of structure and properties of nanoparticles. In this review, we summarize new approaches for EXAFS data analysis that incorporate particle structure modeling into the process of structural refinement.

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In situ formation of hydrides and carbides in palladium catalyst: When XANES is better than EXAFS and XRD

Cited by 114 publications

References 95 publications

Chemical Synthesis and Characterization of Pd/SiO2: The Effect of Chemical Reagent

Chemical Synthesis and Characterization of Pd/SiO2: The Effect of Chemical Reagent

Revealing the Structure and Mechanism of Palladium during Direct Synthesis of Hydrogen Peroxide in Continuous Flow Using Operando Spectroscopy

Solving the Structure and Dynamics of Metal Nanoparticles by Combining X-Ray Absorption Fine Structure Spectroscopy and Atomistic Structure Simulations

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