Hydrogen Motion in Metals

Comment on “Structural and Electronic Properties of the Hydrogenated ZrCr2 Laves Phases”

“…By temperaturedependent NMR measurements, two diffusion processes could be found in hexagonal ZrCr 2 H 0.5 and cubic ZrCr 2 H 0.45 : a fast localized hydrogen motion between [Zr 2 Cr 2 ] sites, thus forming a hexagon of diffusion pathways, and a slower hopping from one such hexagon to a neighboring one. 12 The vast knowledge on diffusion processes in Laves phase hydrides 13 does not back the speculation given in ref 1 that the formation of H 2 plays a role in hydrogen diffusion.…”

Deuterium exchange dynamics in Zr2NiD4.8 studied by 2H MAS NMR spectroscopy

“…The kinetics of the hydrogen absorption and desorption processes will often determine the conditions for successful and efficient operation of proposed devices. Knowledge of the hydrogen diffusion parameters can provide valuable insights during selection and development of appropriate candidates in addition to gaining better understanding of the role of crystal structures and compositions on the fundamental transport mechanisms in the hydride phases [4,5] Nuclear magnetic resonance (NMR) provides information on both local (e.g., hops among a few closely separated sites or rotations of covalently bonded ions) and long-range (e.g., translations) motions from behavior of spectra and several kinds of relaxation times as described in various reviews [6,7]. The most common approach to obtain diffusion parameters using NMR is to measure the spectra or relaxation times over a temperature range appropriate for a given hydride, which are generally analyzed by well-developed microscopic models based upon an Arrhenius relations [6] with an attempt frequency and activation energy (E a ).…”

“…The most common approach to obtain diffusion parameters using NMR is to measure the spectra or relaxation times over a temperature range appropriate for a given hydride, which are generally analyzed by well-developed microscopic models based upon an Arrhenius relations [6] with an attempt frequency and activation energy (E a ). Over the years, NMR studies have been performed on nearly all binary metal hydrides and many intermetallic and alloy hydrides [4,5,6,7]. Unfortunately, these measurements are often insufficient to given more detailed assessments of the specific roles from multiple H-site occupancies on the diffusion processes in the more complicated host structures.…”

¹H NMR Study of Hydrogen Site Occupancy in Hydrides of Disordered Ti-V and Ti-V-Cr Alloys

“…In such perspectives, deeper knowledge on local structure and hydrogen mobility are helpfully required. Appreciable enlightening of main characteristics (static and dynamics) can be provided using nuclear magnetic resonance (NMR) method which is an especially powerful tool to investigate metal hydrogen systems [1,2].…”