Probing Nanoalloy Structure and Morphology by X-Ray Scattering Methods

Andreazza, Pascal

doi:10.1007/978-1-4471-4014-6_3

Cited by 14 publications

(19 citation statements)

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“…EXAFS is also an invaluable complement to atomic-resolution electron microscopy for gaining statistical (averaged) information on metal dispersion, and thereby checking the homogeneity of SAC samples [20,38]. X-ray scattering techniques [39,40] such as X-ray diffraction [41,42] and small-angle X-ray scattering (SAXS) [43] allow one to determine in situ the atomic-level (crystalline phase and domain size, atomic order/disorder) and nanoscale (NP size, shape and spatial distribution) structural characteristics of nanocatalysts, respectively, in the course of their elaboration or evolution under catalytic conditions. Wide angle X-ray scattering (WAXS) appears better suited to investigate inhomogeneous atom arrangements in weakly crystalline nano-objects (e.g.…”

Section: Photon-based Techniquesmentioning

confidence: 99%

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Restructuring effects of the chemical environment in metal nanocatalysis and single-atom catalysis

Piccolo

2021

Catalysis Today

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Metal-based heterogeneous catalysts mostly consist of supported nanoparticles of a few nanometers in size, because these objects provide a good compromise between exposed active surface area and structural stability. However, far from being static, heterogeneous catalysts constantly evolve under reaction conditions, thereby creating and removing surface sites in response to their gaseous or liquid reactive environment. Modern ex situ and in situ investigations have shown that nanocatalysts at work can face a number of deep restructuring phenomena, such as morphological change, compound formation, segregation, leaching, as well as redispersion and other metal-support interaction effects. Recently emerging single-atom catalysts are -like subnanometric clusters -especially sensitive to their chemical environment. Using examples from the recent literature with a particular emphasis on operando characterization studies, this article reviews the main dynamic effects induced by the reaction medium on nanocatalysts (including nanoalloy catalysts) and single-atom catalysts.

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Section: Photon-based Techniquesmentioning

confidence: 99%

“…Besides XPS, surface-science techniques such as scanning probe microscopies like STM [56], and adaptations of X-ray and IR techniques to planar systems such as GISAXS [39,43], SXRD [57,58] and IRAS [59], provide valuable information on the interaction of model catalysts with chemical environments [6,60].…”

Section: Photon-based Techniquesmentioning

confidence: 99%

Restructuring effects of the chemical environment in metal nanocatalysis and single-atom catalysis

Piccolo

2021

Catalysis Today

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“…Pt NPs obtained for the three Argon working pressures (1.0, 4.0 and 9.0 Pa) are characterized using SAXS experiments [32][33][34] to determine the influence of the argon pressure on the Pt NPs mean size. SAXS is a very powerful tool for investigating in situ NPs without manipulating or destroying the samples.…”

Section: Characterization Of As-synthesized Pt Nps By Saxsmentioning

confidence: 99%

Synthesis of Platinum Nanoparticles by Plasma Sputtering onto Glycerol: Effect of Argon Pressure on Their Physicochemical Properties

et al. 2021

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Electrochemical energy conversion devices, such as polymer electrolyte membrane fuel cells (PEMFCs) and PEM electrolyzers are considered as possible candidates for integration in future renewable energy network 1,2 . However, the oxygen reduction reaction (ORR) kinetic at the cathode of a PEMFC is slow and the overpotential at the cathode is generally high (higher than 0.200 V), whereas that of the hydrogen oxidation at the anode is ca. 0.050 V 3 . For this purpose, platinum (Pt) or its alloys are often required as electrocatalyst because of their excellent catalytic activity for the ORR 4 . Electrocatalysis involves surface reactions, therefore, a high surface/inner atoms ratio is desirable to improve the Pt nanoparticles (Pt NPs) performance. NPs with size ranging between 2 to 4 nm are generally preferred 5 .NPs can be obtained through various physical, chemical or physicochemical routes 6,7 . The chemical methods are very versatile in terms of controlling NPs shape and size by varying the reaction conditions. However, NPs chemical synthesis requires additives, which generate by-products difficult to remove and NPs with limited purity. In contrast, physical methods (such as sputtering, thermal evaporation, laser ablation, spark discharge…) on solid substrates avoid the use of additives, allowing the production of pure metallic NPs with the same material composition as that of the starting material. Moreover, these methods can be considered as green approaches using non-toxic reducing agents and avoiding the formation of byproducts 8 . Among physical techniques for preparing electrocatalytic NPs, magnetron sputtering is known to produce efficient Pt NPs deposited on a microporous carbon layer 9 or on a polymer electrolyte membrane 10 to directly fabricate the catalytic layer composite. However, using the sputtering method for the deposition of metal NPs onto such substrates often makes the control of the NPs properties (size, dispersion and morphology) complex. Moreover, this process makes also difficult to create three phase boundaries by the addition of ionomer in comparison with the conventional liquid ink preparation techniques based on classical chemical processes for carbon supported NPs. A solution consists in synthesizing NPs directly in a liquid phase using magnetron sputtering technique and to disseminate the NPs onto a porous substrate. This innovative method

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“…En effet, la taille et la morphologie des particules métalliques sont des paramètres importants de l'activité (vitesse de réaction aux électrodes) et de la sélectivité (production d'eau à la cathode) des matériaux catalytiques [8]. Pour comprendre comment la pulvérisation plasma peut permettre le dépôt/croissance d'agré-gats appropriés pour les électrodes de piles à combustible, nous avons mené une étude conjointe de microscopie électronique en transmission et de diffusion de rayons X aux petits angles en incidence rasante (GISAXS, voir encadré 3) [9,10].…”

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