Hydrogen absorption in Ni and Pd: A study based on atomistic calculations

Crespo, E.A.; Ruda, M.; Debiaggi, S. Ramos de

doi:10.1016/j.ijhydene.2007.12.010

Cited by 6 publications

(4 citation statements)

References 4 publications

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“…For periodic bulk simulations, a TPμ H2 N Pd ensemble, with constant pressure and variable volume, is required to allow for lattice expansion upon hydrogen uptake. Hence, we have extended the previously reported GC-MC/MD method to include stochastic volume changes in a fixed pressure ensemble, similar to the GC-MC methods employed to investigate Pd/H systems by Ray and co-workers , and by Debiaggi and co-workers. − The following MC moves are available in the TVμ H2 N Pd ensemble: (1) insertion of a hydrogen atom into the system at a random position, (2) deletion of a randomly selected hydrogen atom from the system, or (3) displacement of a hydrogen atom to a new random position in the system. The same MC moves are available in the TPμ H2 N Pd ensemble, with the addition of a volume-change MC move that allows the system volume to cubically expand or contract by a randomly selected amount.…”

Section: Theory and Methodsmentioning

confidence: 99%

A ReaxFF Investigation of Hydride Formation in Palladium Nanoclusters via Monte Carlo and Molecular Dynamics Simulations

2014

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Palladium can readily dissociate and absorb hydrogen from the gas phase, making it applicable in hydrogen storage devices, separation membranes, and hydrogenation catalysts. To investigate hydrogen transport properties in Pd on the atomic scale, we derived a ReaxFF interaction potential for Pd/H from an extensive set of quantum data for both bulk and surface properties. Using this potential, we employed a recently developed hybrid grand canonical-Monte Carlo/molecular dynamics (GC-MC/MD) method to derive theoretical hydrogen absorption isotherms in Pd bulk crystals and nanoclusters for hydrogen pressures ranging from 10–1 atm to 10–14 atm, and at temperatures ranging from 300 to 500 K. Analysis of the equilibrated cluster structures reveals the contributing roles of surface, subsurface, and bulk regions during the size-dependent transition between the solid solution α phase and the hydride β phase. Additionally, MD simulations of the dissociative adsorption of hydrogen from the gas phase were conducted to assess size-dependent kinetics of hydride formation in Pd clusters. Hydrogen diffusion coefficients, apparent diffusion barriers, and pre-exponential factors were derived from MD simulations of hydrogen diffusion in bulk Pd. Both the thermodynamic results of the GC-MC/MD method and the kinetic results of the MD simulations are in agreement with experimental values reported in the literature, thus validating the Pd/H interaction potential, and demonstrating the capability of the GC–MC and MD methods for modeling the complex and dynamic phase behavior of hydrogen in Pd bulk and clusters.

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Section: Theory and Methodsmentioning

confidence: 99%

A ReaxFF Investigation of Hydride Formation in Palladium Nanoclusters via Monte Carlo and Molecular Dynamics Simulations

2014

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“…29 A comparison based on Pd versus Pd-Ni alloy computed 27 that absorption energy per H atom of pure Pd is À0.126 eV compared to À0.015 eV for Pd 33 Ni 67 , meaning lower stability of hydrogen in the Pd-Ni alloy until a larger ΔE is applied. Nevertheless, hydrogen incorporated so, may be located at the surface and subsurface layers of the nanoparticles, as octahedral voids of the fcc lattice are preferred over relatively smaller-sized tetrahedral.…”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless, hydrogen incorporated so, may be located at the surface and subsurface layers of the nanoparticles, as octahedral voids of the fcc lattice are preferred over relatively smaller-sized tetrahedral. [28][29][30] This causes the lattice to expand by the change in the lattice parameter nearly about 1.8% in Pd 33 Ni 67 27 : multiplying which with the bulk modulus, K % 180 Gpa, yielded strain-induced pressure (P 5 3eK) to be 9.72 GPa 18,28 Pressure dependence of magnetism in Pd-Ni alloys is well known over decades attributed to hybridization effect between 1s electrons of hydrogen and 3d metals. This can affect magnetization.…”

Section: Discussionmentioning

confidence: 99%

Switching magnetic order in nanoporous Pd–Ni by electrochemical charging

Ghosh

2013

J. Mater. Res.

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The present work demonstrates an isothermal reversible variation of magnetization in nanoporous Pd 67 Ni 33 alloy during continuous charging and discharging of the alloy electrode in 1-M KOH solution. A custom-built electrochemical cell, containing the sample as working electrode performed the in situ charging experiments inside an extraction magnetometer at a constant applied magnetic field. The metal-electrolyte response was examined by varying the electrode potential, which apart from polarizing nanoporous structure, may also lead to electrodissociation of the electrolyte medium, being aqueous in nature. The result therefore analyzed hydrogenation as the key parameter for the observed reversible magnetization in the transition metal alloy at room temperature. In addition, electrochemical reactivity due to surface oxidation at the positive potential has been discussed, considering that a change in the band structure is also possible at the negative potential regime due to hydrogenation through cyclic voltammetry study.

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“…Recently, we used the same cluster approach to model several defects such as dislocation [23], vacancies [24,25], grain boundaries [26] and stacking faults [27,28], being this representation useful to study local effects during interactions with point and line defects. The same approach was also used successfully by Crespo et al [29] to model H absorption on Pd and Ni.…”

Section: The Pd Dislocation Modelmentioning

confidence: 97%