Hydrogen Flux through Size Selected Pd Nanoparticles into Underlying Mg Nanofilms

Abstract

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.

Magnetron-sputtered copper nanoparticles: lost in gas aggregation and found by in situ X-ray scattering

“…The method has acquired particular popularity as is evidenced by an increasing number of papers that have been published in recent years. Single-metal, [4][5][6][7][8][9][10][11][12][13][14][15] alloyed [16][17][18][19][20][21][22][23][24][25][26] and heterostructured NPs [27][28][29][30][31][32][33][34][35][36][37][38][39][40] have been successfully synthesized.…”

Computational Modeling of Nanoparticle Coalescence

“…Further, the implicit assumption of isotropic surfaces in the continuous phenomenological models would also prove wrong, as faceted clusters might be terminated by different surfaces with big differences in their surface diffusion coefficients . Finally, utilizing values obtained experimentally from bulk materials for properties at the nanoscale might incur problems related to the measurement methodologies, as these values were usually apparent values that were determined by numerous defects often present in bulk structures …”

“…Clearly, for nonspherical clusters the uniform curvature argument does not hold true as a stimulus for atomic diffusion. [37] With the advancement of characterization techniques which enabled the experimental observation of nanoparticle coalescence, it became evident that the constant rates that continuum modeling predicted for the sintering process was also a very rough approximation. [32,33] Further, the implicit assumption of isotropic surfaces in the continuous phenomenological models would also prove wrong, as faceted clusters might be terminated by different surfaces with big differences in their surface diffusion coefficients.…”

Atomic-scale structure and chemical sensing application of ultrasmall size-selected Pt nanoparticles supported on SnO2

“…A wide range of nanoparticle functionalities has been achieved with this method, e.g., percolating nanoparticle films for chemoresistive sensing, [24][25][26][27][28][29][30] nanoparticle-decorated metal oxide nanowire devices for chemoresistive sensing, [31][32][33] supported nanoparticles for catalysis and electrochemistry, [34][35][36][37] magnetic nanoparticles, 30,[38][39][40] nanoparticles embedded in multi-layered anodes for lithium ion batteries 41 and nanoportals for hydrogen storage applications. 42 Here, we demonstrate a new approach for the surface functionalization of micro-machined chemical sensor devices realized in complementary metal-oxide-semiconductor (CMOS) technology, in particular by depositing ultrasmall Pt nanocatalysts by magnetron sputtering inert-gas condensation onto nanocrystalline SnO 2 thin films integrated on a suspended microhotplate platform. We focus on studying the sensing performance for the toxic gas carbon monoxide (CO) in humid atmosphere, which is highly relevant for safety applications as well as environmental monitoring.…”