Hydrogenation of Mg nanofilms catalyzed by size-selected Pd nanoparticles: Observation of localized MgH2 nanodomains

Kumar, Sushant; Singh, Vidyadhar; Cassidy, Cathal; Pursell, Christopher J.; Nivargi, Chinmay; Clemens, Bruce M.; Sowwan, Mukhles

doi:10.1016/j.jcat.2016.01.018

Cited by 15 publications

(9 citation statements)

References 55 publications

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“…The rather uniform distribution of the deposited NPs is clearly demonstrated in the exemplary low-magnification STEM images of Pd 3 Mg 20 and Pd 5 Mg 20 shown in Figure a,d, respectively, in accordance with previous studies. ,, The presence of evenly distributed Pd NPs on the oxidized surface of the Mg thin film was also verified via elemental mapping by EDX (Figure S1). High-magnification STEM images of both Pd 3 Mg 20 and Pd 5 Mg 20 reveal quasi-spherical polycrystalline particles, as shown in Figure b,e, respectively.…”

Section: Resultssupporting

confidence: 89%

Single Nanoparticle Activities in Ensemble: A Study on Pd Cluster Nanoportals for Electrochemical Oxygen Evolution Reaction

et al. 2019

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Comprehensive understanding of the electrochemical activity of single nanoparticles (NPs) is in critical need for opening new avenues in the broad field of electrochemistry. Published reports on single-NP electrocatalysts typically include complicated and difficult methods of synthesis and characterization; moreover, these methods usually fail to provide a reliable way to measure the activities of individual NPs within larger ensembles of particles, i.e., in real-life nanocatalyst systems. In the present work, we synthesized from the gas phase Pd NPs that act as nanoportals for electron transfer within surfaceoxidized Mg thin films. The physical synthesis method provided excellent control over the deposition density and, hence, enabled the design of a system where each individual open nanoportal forms an independent active single-NP electrode (SNPE). Being uncoupled from one another, these SNPEs contribute separately toward the total electrocatalytic activity while simultaneously providing a measure of their average, individual activities. We were thus able to fabricate a stable, steady-state electrode for the electrochemical oxygen evolution reaction (OER) and to study the activity and stability of the SNPEs over a period of 20 days; the former depended on the size of the NPs, while the latter depended on the SNPEs' resistance to aerial oxidation. The remarkable stability of the ensemble catalysts under OER conditions proves that this concept can be used for further studies on the activities of different single NPs in numerous real-life systems.

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Section: Resultssupporting

confidence: 89%

Single Nanoparticle Activities in Ensemble: A Study on Pd Cluster Nanoportals for Electrochemical Oxygen Evolution Reaction

et al. 2019

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“…Cluster nucleation, growth, and coalescence lead to the formation of Pd nanoparticles, which pass through a quadrupole mass filter (not shown) for selection according to their sizes . The resultant Pd nanoparticles with a narrow size distribution , are transported to the main chamber through a pressure differential and are subsequently deposited on the sample in the soft landing regime . A high-resolution TEM micrograph of a representative Pd nanoparticle can be seen in Figure b, which exhibits single-crystalline structure with lattice parameters corresponding to the face-centered cubic Pd lattice.…”

Section: Resultsmentioning

confidence: 99%

Thermal Oxidation of Size-Selected Pd Nanoparticles Supported on CuO Nanowires: The Role of the CuO–Pd Interface

et al. 2017

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The structure of heterogeneous nanocatalysts supported on metal oxide materials and their morphological changes during oxidation/reduction processes play a crucial role in determining the resulting catalytic activity. Herein, we study the thermal oxidation mechanism of Pd nanoparticles supported on CuO nanowires by combining in situ environmental transmission electron microscopy (TEM), ex situ experiments, and ab initio density functional theory (DFT) calculations. High-resolution TEM imaging assisted by geometric phase analysis enabled the analysis of partially oxidized, fully oxidized, and distinct onion-like Pd nanoparticles with subsurface dislocations. Furthermore, preferential crystalline orientations between PdO nanoparticles and the CuO nanowire support have been found. Hence, the CuO–Pd interface is crucial for the thermal oxidation of Pd nanoparticles, as corroborated by electron energy loss spectroscopy and DFT calculations. The latter revealed a considerably lower energy barrier for penetration of oxygen into the Pd lattice at the CuO–Pd interface, promoting nanoparticle oxidation. The obtained results are compared with those of literature reports on different material systems, and potential implications for catalysis and chemoresistive sensing applications are discussed.

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“…Pd NPs overlaid on the surface of a Mg film can locally inhibit the oxidation of Mg, [27] forming localized metal-metal interfaces on otherwise surface-oxidized Mg films. In this context, a potential hydrogenation mechanism through Pd NP nanoportals was proposed for an underlying surface-oxidized Mg film, as summarized in Figure 1.…”

Section: Model For the Hydrogenation Of A Mg Film Through Pd Nanoportalsmentioning

confidence: 99%

“…In this context, a potential hydrogenation mechanism through Pd NP nanoportals was proposed for an underlying surface-oxidized Mg film, as summarized in Figure 1. [27,28] Upon hydrogen exposure, hydrogen molecules adsorb and dissociate to individual atoms on the surface of the Pd NPs (A), which subsequently diffuse through interstitial octahedral sites of the Pd NPs toward the interface with the substrate. [29][30][31] If this is a Pd/MgO interface (B), hydrogen penetration is suppressed; if it is a Pd/Mg interface (C), hydrogen atoms diffuse through it, eventually forming MgH 2 .…”

Section: Model For the Hydrogenation Of A Mg Film Through Pd Nanoportalsmentioning

confidence: 99%

“…Hence, the idea of Pd nanoparticles (NPs) acting as nanoportals for hydrogen diffusion into oxidized Mg films was introduced to enable the decoupling and simultaneous study of both obstacles. [27,28] Herein, we investigate the crucial factors that can affect the hydrogen sorption behavior in a Pd NP-catalyzed Mg film. In doing so, we explore all the implicit and explicit assumptions of the proposed mechanism, both theoretically and experimentally, with an emphasis on the role of the various potential interfaces.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen Flux through Size Selected Pd Nanoparticles into Underlying Mg Nanofilms

Kumar

Pavloudis

Singh

et al. 2017

Advanced Energy Materials

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The application of Mg as a potential hydrogen storage material has been hindered due to the slow absorption rate of hydrogen in Mg films. Herein, we explore the hydrogenation process theoretically using DFT calculations, and compare the energy barriers for hydrogen diffusion through Pd nanoparticle/Mg film interfaces and their variations, i.e. Pd(H)/Mg(O).Decomposing the mechanism into basic steps, we show that Pd undergoes a strain-induced crystallographic phase transformation near the interface, and indicate that hydrogen saturation of Pd nanoparticles enhances their efficiency as nanoportals. Using energetic arguments, we explain why hydrogen diffusion is practically prohibited through native Mg oxide, and seriously suppressed through existing hydride domains. We experimentally investigate hydrogen flux through the nanoportals in Pd nanoparticle-decorated Mg films by PCT hydrogenation measurements, and demonstrate the effect of the surface oxide layer and film thickness on hydrogenation kinetics. We theoretically calculate an r~t 1/3 relationship for the radial growth of hemispherical hydride domains, and confirm this relationship by AFM. The diffusion constant of hydrogen in Mg films is estimated as D H film ≈8×10 -18 m 2 s -1 , based on TEM characterization. Our unique nanoportal configuration allows direct measurement of hydride domain sizes, thus forming a model system for the experimental investigation of the hydrogenation process in any material.

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Hydrogenation of Mg nanofilms catalyzed by size-selected Pd nanoparticles: Observation of localized MgH2 nanodomains

Cited by 15 publications

References 55 publications

Single Nanoparticle Activities in Ensemble: A Study on Pd Cluster Nanoportals for Electrochemical Oxygen Evolution Reaction

Single Nanoparticle Activities in Ensemble: A Study on Pd Cluster Nanoportals for Electrochemical Oxygen Evolution Reaction

Thermal Oxidation of Size-Selected Pd Nanoparticles Supported on CuO Nanowires: The Role of the CuO–Pd Interface

Hydrogen Flux through Size Selected Pd Nanoparticles into Underlying Mg Nanofilms

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