Supported metal NPs on magnesium using SCFs for hydrogen storage: Interface and interphase characterization (original) (raw)
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Mg-Based Nanocomposites with High Capacity and Fast Kinetics for Hydrogen Storage
The Journal of Physical Chemistry B, 2006
Magnesium and its alloys have shown a great potential in effective hydrogen storage due to their advantages of high volumetric/gravimetric hydrogen storage capacity and low cost. However, the use of these materials in fuel cells for automotive applications at the present time is limited by high hydrogenation temperature and sluggish sorption kinetics. This paper presents the recent results of design and development of magnesiumbased nanocomposites demonstrating the catalytic effects of carbon nanotubes and transition metals on hydrogen adsorption in these materials. The results are promising for the application of magnesium materials for hydrogen storage, with significantly reduced absorption temperatures and enhanced ab/desorption kinetics. High level Density Functional Theory calculations support the analysis of the hydrogenation mechanisms by revealing the detailed atomic and molecular interactions that underpin the catalytic roles of incorporated carbon and titanium, providing clear guidance for further design and development of such materials with better hydrogen storage properties.
Journal of Alloys and Compounds, 2009
Both hydrogen absorption and desorption, in the range 200-300 and 260-330 • C, respectively, of magnesium particles decorated with metallic nanoplots elaborated by Supercritical Fluid Chemical process are studied. The absorption data are fitted using Avrami-Erofeev model to first order. Unexpectively, magnesium decorated with copper nanoparticles lead to relatively high rates of sorption (absorption rate at 300 • C and desorption rate at 330 • C of about 0.4 wt%H min −1) but its activation energy remains high (∼70 kJ mol −1). The presence at the interface of MgCu 2 , acting as a chemical link between the nanoCu and the magnesium particle could be responsible for such behavior. Palladium nanoparticles react with magnesium during cycling so that the catalytic effect is decreasing with cycling and finally does not exist anymore after 10 cycles. Finally, the best results are obtained for the nanocomposite of magnesium with nickel nanoparticles for which the sorption rates are comparable with the ones obtained for optimized BM samples with catalysts, but with a lower energy cost of the process.
Magnesium nanoparticles with transition metal decoration for hydrogen storage
Journal of Nanoparticle Research
We report on the hydrogen storage behaviour of Mg nanoparticles (NPs) (size range 100 nm-1 mu m) with metal-oxide core-shell morphology synthesized by inert gas condensation and decorated by transition metal (TM) (Pd or Ti) clusters via in situ vacuum deposition. The structure and morphology of the as-prepared and hydrogenated NPs is studied by electron microscopy, X-ray diffraction including in situ experiments and X-ray absorption spectroscopy, in order to investigate the relationships with the hydrogen storage kinetics measured by the volumetric Sieverts method. With both Pd and Ti, the decoration deeply improves the hydrogen sorption properties: previously inert NPs exhibit complete hydrogenation with fast transformation kinetics, good stability and reversible gravimetric capacity that can attain 6 wt%. In the case of Pd-decoration, the occurrence of Mg-Pd alloying is observed at high temperatures and in dependence of the hydrogen pressure conditions. These structural transforma...
Applied Catalysis A: General, 2006
An effective catalyst doping method was developed for directly depositing nano-particles of various metal catalysts (palladium, platinum and ruthenium) on the outer surface of magnesium powders through a wet chemistry process. The catalyst-doped magnesium was characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). Catalysts of nano-meter size were uniformly deposited on the outer surface of the magnesium particles. The hydrogen storage and hydrogen release properties of magnesium and catalysts-doped magnesium were measured in situ by the tapered element oscillating microbalance (TEOM), and also by the volumetric method. Both the hydrogen absorption and hydrogen release kinetics of magnesium were significantly improved by doping the nanoparticle catalysts. Among the three metals-doped and examined, palladium showed the best catalytic effect. Upon doping 0.5 mol% nano-particle palladium, the hydrogen absorption and hydrogen release rates of magnesium increased 1 and 14 times, respectively, as revealed by the dynamic measurement of storage/release by TEOM, which indicated a strong catalytic effect.
Nanoscale Mg-based materials for hydrogen storage
International Journal of Hydrogen Energy, 2008
Hydrogen storage materials research has entered a new and exciting period with the advance of the nanocrystalline alloys, which show substantially enhanced absorption/desorption kinetics, even at room temperatures. In this work, we study experimentally the structure and electrochemical properties of nanocrystalline Mg2Cu, (Mg1-xMx)2Ni alloys, as well as Mg2Cu/M′ and (Mg1-xMx)2Ni/M′ (x=0, 0.5; M=Al, Mn; M′=C, Pd) nanocomposites. These materials were
Exploring several different routes to produce Mg- based nanomaterials for Hydrogen storage
IOP Conference Series: Materials Science and Engineering, 2014
Severe mechanical processing routes based on high-energy ball milling (HEBM) or severe plastic deformation (SPD) can be used to produce Mg nanomaterials for hydrogen storage applications. In the last few years, we have been exploring in our research group different SPD processing routes in Mg systems to achieve good activation (first hydrogenation) and fast H-absorption/desorption kinetics, combined with enhanced air resistance. In this paper, we compare SPD techniques applied to Mg with HEBM applied to MgH2. Both advanced-melt spinning (MS), high-pressure torsion (HPT)-and more conventional-cold rolling (CR), cold forging (CF)-techniques are evaluated as means of production of bulk samples with very refined microstructures and controlled textures. In the best SPD processing conditions, attractive H-absorption/desorption kinetic properties are obtained, which are comparable to the ones of MgH2 milled powders, even if the needed temperatures are higher-350°C compared to 300°C.CR and CF stand out as the processes with higher potential for industrial application, considering the level of the attained hydrogen storage properties, its simplicity and low cost.
Mg-based hydrogen storage materials: Surface segregation in Mg2Cu and related catalytic effects
Materials Research Bulletin, 1980
Fresh surfaces of Mg2Cu polycrystals cleaved in UHV have been investigated by AES, XPS and X-ray induced AES at room temperature. They show chemical decomposition of the surface leading to pronounced increase of surface Mg content. In contrast to the Mg the Cu remains essentially metallic, even on air exposed samples. It is suggested that this segregation prevents the formation of a compact oxide or hydroxide layer, thereby enabling dissociation of molecular hydrogen at the metallic Cu precipitations and/or the metallic Mg2Cu subsurface. The results support comparable conclusions drawn earlier for LaNi5, FeTi and Mg2Ni.
Bimetallic Fe–V catalyzed magnesium films exhibiting rapid and cycleable hydrogenation at 200 °C
Applied Physics Letters, 2010
We examined hydrogen sorption in 1.5 m thick Mg-Fe-V films, using the binary alloys as baselines. At 200°C both Mg-V and Mg-Fe-V absorb in tens of seconds, and desorb in tens of minutes. The ternary alloys show minimal kinetic or capacity degradation even after 105 absorption/ desorption cycles. Pressure-composition isotherms yield the well-known enthalpies of ␣-MgH 2 formation ͑decomposition͒, agreeing with x-ray diffraction results. The x-ray spectrum also shows a broad hump centered near ͑011͒ reflection of CsCl-type Fe-V phase. Our hypothesis is that a densely distributed nanoscale Fe-V acts both as a potent hydrogen dissociation catalyst and a heterogeneous nucleation site.
Combustion-type hydrogenation of nanostructured Mg-based composites for hydrogen storage
International Journal of Energy Research, 2009
In this study Reactive Ball Milling in hydrogen gas was used to synthesize nanostructured hydrogenated composites of Mg and V-based alloy. After hydrogen desorption, the nanocomposites exhibited a dramatic facilitation of the rate of H absorption by Mg and reduction of the temperature of onset of hydrogenation. These favourable changes were caused by a synergy of catalytic effect of the V-based alloy on hydrogen absorption by Mg and heat release caused by exothermic hydrogen absorption by the V-based alloy. When the initial interaction temperature exceeded a threshold, rather low, value of 20-1251C, depending on the H 2 pressure, composition of the sample and its total amount, a combustion-type hydrogenation took place. With optimal interaction parameters applied, H absorption was completed in just 5-70 s and was accompanied by a significant heat release. The observed features can be utilized to reach fast recharge of the Mg-based H stores and to develop efficient heat management systems.