Hydrogen storage characteristics of nanograined free-standing magnesium–nickel films

Abstract

Free-standing magnesium-nickel (Mg-Ni) films with extensive nanoscale grain structures were fabricated using a combination of pulsed laser deposition and film delaminating processes. Hydrogen sorption and desorption properties of the films, free from the influence of substrates, were investigated. Oxidation of the material was reduced through the use of a sandwiched free-standing film structure in which the top and bottom layers consist of nanometerthick Pd layers, which also acted as a catalyst to promote hydrogen uptake and release. Hydrogen storage characteristics were studied at three temperatures, 296, 232, and 180°C, where multiple sorption/desorption cycles were measured gravimetrically. An improvement in hydrogen storage capacity over the bulk Mg-Ni target material was found for the free-standing films. As shown from a Van't Hoff plot, the thermodynamic stability of the nanograined films is similar to that of Mg 2 Ni. These results suggest that free-standing films, of which better control of material compositions and microstructures can be realized than is possible for conven- The need for a safe, reliable, and efficient method of hydrogen storage for transportation applications is stronger now than ever before. This need has led to a continuous increase in both the breadth and depth of research in the field of hydrogen storage. Compressed gas, liquid hydrogen, and various chemical and metal hydride approaches have been proposed and studied over the past 20 years [1]. Despite extensive research effort, no definitive best method or best material has been identified. Weaknesses and difficulties for every method and material exist. Examples are the poor volumetric storage of hydrogen as a compressed gas, the boil off of liquid hydrogen, the poor irreversibility of chemical and metal hydrides [2].Metal hydrides consisting of a high fraction of lightweight elements have attracted much attention. The basic storage mechanisms of hydrogen by physisorption and chemisorption as well as the importance of catalysts have been elucidated [3][4][5]. More recently, the benefits of using nanometer-sized materials have also been explored [6][7][8]. Through nanostructuring, improvements in hydrogen uptake and release kinetics at little cost to hydrogen sorption capacities are possible. There are, however, very few material synthesis approaches that can generate a sufficient quantity of nanostructured light-weight metals (which are generally reactive upon exposure toward air and water) for reliable testing of their hydrogen storage properties. The majority of existing studies of metal hydrides are based on the characterization of ball-milled powders. For many materials of

The clamping effect in the complex hydride Mg2NiH4 thin films

“…3), though those authors used a substantially smaller temperature range, T < 363 K. 4 There are no data on the desorption thermodynamics of complex hydride Mg 2 NiH 4 lms except for free-standing thick (1.6 mm) Mg 2 Ni. The desorption pressures of these free-standing Mg-Ni lms, determined gravimetrically in the range 453-669 K by Rogers et al, 6 are consistent with bulk data on Mg 2 NiH 4 , but no thermodynamic parameters were given. The thermodynamic parameters of bulk Mg 2 NiH 4 have been extensively investigated over the last few decades.…”

An overview of progress in Mg-based hydrogen storage films*

“…[41][42][43][44][45][46][47][48][49][50][51] If the plasma is not generated by the bombardment of the particles, which are accelerated in the electric field, with the target, but by the interaction of pulsed laser with the target, then the deposition is called pulsed laser sputtering deposition or pulsed laser deposition (PLD). [52,53] For Mg-based thin films, hydrogenation can be achieved in two ways: air-exposed hydrogenation and plasma-based hydrogenation, which is realized in reactive sputtering. In addition, if between film deposition process and plasma-based hydrogenation film is air-exposed, then the deposition is called plasma-based ex situ hydrogenation.…”

Frontiers in Applied Atomic Layer Deposition (ALD) Research

“…It is worth mentioning that metal-organic HSD are also extensively studied and the reader is referred to [196] for an excellent review on that topic. Although fabrication of HSD by CVD [192,195] and PVD [191,193,[197][198][199][200][201][202][203][204] techniques has been demonstrated in the past, there aren't as many publication of device production made by ALD. Ten Eyck, G. A., et al studied the ALD formation of 2-5nm thin Palladium (Pd) films on tantalum, silica and on a parylene-N polymer for possible future use for HSD [205,206].…”