Palladium mixed-metal surface-modified AB₅-type intermetallides enhance hydrogen sorption kinetics

Abstract

Surface engineering approaches were adopted in the preparation of advanced hydrogen sorption materials, based on 'low-temperature', AB 5 -type intermetallides. The approaches investigated included micro-encapsulation with palladium and mixed-metal mantles using electroless plating. The influence of micro-encapsulation on the surface morphology and kinetics of hydrogen charging were investigated. It was found that palladium-nickel (Pd-Ni) co-deposition by electroless plating significantly improved the kinetics of hydrogen charging of the AB 5 -type intermetallides at low hydrogen pressure and temperature, after long-term pre-exposure to air. The improvement in the kinetics of hydrogen charging was credited to a synergistic effect between the palladium and nickel atoms in the catalytic mantle and the formation of an 'interfacial bridge' for hydrogen diffusion by the nickel atoms in the deposited layer. The developed surface-modified materials may find application in highly selective hydrogen extraction, purification, and storage from impure hydrogen feeds.http://www.sajs.co.za

Surface-modified advanced hydrogen storage alloys for hydrogen separation and purification

“…XRD studies of the substrate alloy (see [34] for more details) showed that the material contains a major CaCu 5 -type intermetallic phase with the periods of hexagonal unit cell a = 5.00295(1)Å, c = 4.05111(2)Å. The XRD pattern also showed the presence of trace amounts of a mixed rare-earth-nickel oxide (RE 2 NiO 4 ), most probably originating from the surface oxidation of the material.…”

“…Further details on the preparation and characterisation of the surface-modified MH materials are discussed elsewhere [27][28][29][30][31][32][33][34]. Experimental details on hydrogen absorption from gas mixtures will be presented in Section 3.2.…”

Improved Hydrogenation Kinetics of TiMn1.52 Alloy Coated with Palladium through Electroless Deposition

“…The hydrogenation kinetic curves are presented in Figure 4 . In addition, Table 2 presents the results obtained through fitting of the experimental data on the Avrami–Erofeev model, which is described here [ 17 ]. Without vacuum activation, the uncoated TiMn 1.52 alloy exhibits slow hydrogen absorption, accompanied by a long incubation period of ~5 min.…”

“…Surface modification of the TiMn 1.52 alloy was conducted through autocatalytic deposition of Pd in a hypophosphite-based autocatalytic plating bath following the procedure described here [ 17 ]. Prior to palladium deposition, the materials were first sensitized and activated in a palladium–tin (Pd–Sn) colloidal solution [ 17 ] resulting in increased densities of Pd deposition and surface Pd loading on the intermetallide. The activated intermetallide was subsequently suspended in the palladium plating bath.…”

Improvement of hydriding kinetics of LaNi5-type metal alloy through substitution of nickel with tin followed by palladium deposition

“…Nevertheless, more energy associated with hydrogen compression is not economically favoured [3]. The most promising way is to store hydrogen in solid absorbents, such as metal alloys in which hydrogen bound to these materials to form metal hydrides [4]. An attractive feature of solid-state storage is that the absorption of hydrogen using many of these metal alloy materials is reversible, thereby reducing operational costs [5].…”