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The effect of microwave (MW) irradiation on the hydrogen sorption properties of magnesium powder is explored in the present work. MgH 2 – 10 wt.% CFs (CFs = Carbons Fibers) was prepared by hand mixing, dehydrogenated under microwave irradiation for 20 s and then hydrogenated/dehydrogenated at about 300 °C – 1 MPa and 330 °C–0.03 MPa to investigate the effect of microwave irradiation on the solid/gas sorption properties. It has to be noted that the hydrogen absorption capacity and sorption kinetics of the MgH 2 – 10 wt.% CFs mixture increased after dehydriding under MW irradiation. The MgH 2 – 10 wt.% CFs mixture dehydrogenated by microwave irradiation can absorb about 5.8 wt.% and 5.3 wt.% H at 330 and 300 °C, respectively, within 2 h while the as-prepared MgH 2 – 10 wt.% CFs mixture absorb only 4.6 wt.% H within the same duration. It is also demonstrated that MgH 2 – 10 wt.% CFs mixture dehydrogenated by microwave irradiation exhibited good hydrogen desorption properties and, as an example, a microwave irradiated sample could release 5.8 wt.% H within 1 h at 330 °C in comparison to the as-prepared MgH 2 – 10 wt.% CFs mixture which desorbed 4.4 wt.% H within 3 h. Scanning electron microscopy (SEM) images revealed that the particle sizes of the MW dehydrogenated mixture decreased after several solid/gas sorption cycles. This contribute to the improvement of hydrogen storage properties of the microwaves dehydrogenated MgH 2 – 10 wt.% CFs mixture. In addition, the hydrogenated MgH 2 – 10 wt.% CFs mixture show reproducible and better microwave-assisted dehydriding reaction during second microwaves cycle. [ABSTRACT FROM AUTHOR]

In most of the Mg–Al alloys, Al forms with Mg the intermetallic compound Mg 17 Al 12. In order to understand the hydrogen production from the Mg–Al alloys waste by the hydrolysis reaction in "model" seawater (i.e. 3.5 wt % NaCl), hydrolysis with Mg 17 Al 12 was investigated. The effect of ball milling time, the nature of the additives (graphite, NaCl, MgCl 2 and AlCl 3) and the synergetic effects of both graphite and AlCl 3 were investigated. It has been established that increasing ball milling time up to 5 h is necessary to activate the intermetallic and to decrease sufficiently its crystallites and particles size. On one hand, the presence of AlCl 3 provides the best hydrolysis performance (14% of the theoretical hydrogen volume in 1 h). On the other hand, the mixture obtained by simultaneous addition of graphite and AlCl 3 shows the best hydrolysis performances with 16% of the theoretical H 2 volume reached in 1 h. • Mg 17 Al 12 can produce hydrogen by the hydrolysis reaction. • Ball milling with graphite and AlCl 3 are the best additives to improve Mg 17 Al 12 hydrolysis. • Hydrolysis of Mg–Al alloys may be enhanced by ball milling with graphite and AlCl 3. [ABSTRACT FROM AUTHOR]

Abstract: Magnesium hydride could be considered as a good candidate for the hydrolysis reaction because it can be produced at a relatively low cost. However, this reaction is incomplete and very slow because of the formation of a magnesium hydroxide layer on the surface of MgH2 particles. In order to overcome this problem, various treatments such as ball milling with or w/o additives, addition of acids, ultrasounds and increase of temperature, have been tried. Different characterization methods such as XRD, BET, particle size, SEM, etc. have been used to explain the effects of the treatments cited above on the improvement of the kinetics and the yield of the MgH2 hydrolysis reaction. [Copyright &y& Elsevier]

The corrosion behavior of pure Mg 17 Al 12 and the effect of ball milling in presence of additives (i.e. graphite (G) and magnesium chloride (MgCl 2)) are evaluated in 3.5 wt% NaCl aqueous solution using electrochemical polarization and impedance measurements. Pure Mg 17 Al 12 and milled Mg 17 Al 12 without additives and with MgCl 2 present an open current potential (OCP) of −1.2 V/SCE while Mg 17 Al 12 + G shows a slightly higher OCP (+10% maximum). Mg 17 Al 12 corrodes with low kinetics and an increase of corrosion rate for the milled Mg 17 Al 12 is observed. The corrosion current densities (J corr) derived from the Tafel plots, exhibit their corrosion reactivity as follow: Mg 17 Al 12 < Mg 17 Al 12 5h < Mg 17 Al 12 + G 5h < Mg 17 Al 12 + MgCl 2 5h. Electrochemical impedance spectroscopy (EIS) results are in good agreement with the measured J corr. Randles circuit models are established for all samples to explain their surface behavior in the aqueous NaCl solution. The variation of the fitted parameters is attributed either to the effect of ball milling or to the effect of the additive. Our results are helpful in elucidating the effect of ball milling and the additives. • Mg 17 Al 12 corrodes in a 3.5 wt% aqueous solution of NaCl with a corrosion current density of 5.3 μA/cm2. • Mg 17 Al 12 can act as cathode in Mg–Al alloy with an OCP of −1.2 V/SCE. • Electrochemical impedance spectroscopy can explain the effect of ball milling additives. • Ball milling with MgCl 2 increases the corrosion current density by 22 times. [ABSTRACT FROM AUTHOR]

In this work, monometallic (1 wt% of Ru or 5 wt% of Ni) and bimetallic catalysts (1 wt% Ru-5 wt.% Ni) deposited on alumina (Al 2 O 3), magnesium aluminate spinel (MgAl 2 O 4), and yttria-stabilized zirconia (YSZ) were prepared by wet impregnation. The synthesis method of MgAl 2 O 4 was optimized and a well crystallized phase with high specific surface area was obtained by using wet impregnation, as a simple and low cost route, at 800 °C for 2 h. The catalytic activity was compared at atmospheric pressure and 750 °C toward methane dry reforming (DRM) reaction with a molar ratio CH 4 /CO 2 = 1/1 and a Weight Hourly Space Velocity (WHSV) of 60.000 mL g−1.h−1. Catalytic activity classification was obtained as the following: Ni/MgAl 2 O 4 > Ru-Ni/Al 2 O 3 > Ru-Ni/MgAl 2 O 4 > Ru-Ni/YSZ > Ni/Al 2 O 3 > Ni/YSZ > Ru/Al 2 O 3 > Ru/YSZ » Ru/MgAl 2 O 4. Between the different catalysts, 5 wt% Ni/MgAl 2 O 4 catalyst exhibited excellent catalytic activity for DRM. Furthermore, this catalyst was found to be very stable without any deactivation after 50 h under reacting mixture with a low carbon formation rate (3.58 mg C /g cat /h). Such superior activity and stability of MgAl 2 O 4 supported Ni catalyst is consistent with characterization results from BET, XRD, TPR, CO-pulse chemisorption and CHNS analysis. It can be due to a strong interaction between Ni and MgAl 2 O 4 leading to the incorporation of Ni into the spinel lattice and the formation of oxygen vacancies offering a benefit for DRM reaction. Furthermore, it seems that the addition of ruthenium onto Ni/MgAl 2 O 4 decreases the interaction between Ni and the spinel leading to a decrease in the catalyst performance. On the other side, the addition of ruthenium on Ni/Al 2 O 3 leads to an increase in the catalyst stability and efficiency by inhibiting the formation of poorly active phase NiAl 2 O 4 already observed in TPR. • 5 wt% Ni/MgAl 2 O 4 exhibits highest performance in DRM. • Strong Ni/MgAl 2 O 4 interaction leads to incorporation of Ni into spinel lattice. • Ru addition has positive effect on Ni/Al 2 O 3 for DRM contrary to Ni/MgAl 2 O 4 and Ni/YSZ. • 5 wt% Ni/MgAl 2 O 4 : high stability without deactivation after 50 h in reacting mixture. [ABSTRACT FROM AUTHOR]

Hydrolysis is an efficient method to generate in-situ H 2 from Mg-based waste. In order to produce hydrogen from these wastes by the hydrolysis reaction in seawater (i.e. 3.5 wt % NaCl), WE43 alloy was ball milled. WE43 is a magnesium-based alloy (i.e. W stands for Y and the first 4 indicates that the weight % of Y is 4; E stands for RE and the first 3 indicates that the weight % is 3). This alloy is known for its corrosion-resistant and flame-resistant behavior. The effect of the milling time, the nature of the additives (C and Ni) and the synergistic effects of both C and Ni were investigated. It has been established that a pre-milling for 3h is necessary to activate the alloy and to decrease sufficiently its particle size. On one hand, the presence of carbon provides the best hydrolysis performance compared to Ni (maximum theoretical yield reached in 12 min). On the other hand, the chronological order of the addition of both additives during ball milling affects the kinetics of the reaction. The mixture obtained by successive addition of Ni and C shows the best hydrolysis performances with a maximal yield reached in about 9 min. All the results are explained and discussed in terms of microstructural (XRD and SEM-EDS) and morphological (SEM) effects. • Adding C and/or Ni during ball milling of pre-milled WE43 enhances its hydrolysis. • The chronological order of the addition of additives influences the reactivity. • A full hydrolysis reaction of WE43 was obtained within less than 10 min. • Magnesium alloys can be valorized by our method. [ABSTRACT FROM AUTHOR]

Abstract The effects of the Mg content on the microstructure and hydrogen generation kinetics of Mg NdNiMg 15 composites by hydrolysis reaction in seawater (3.5 wt% NaCl) was investigated. The presence of NdNiMg 15 in Mg matrix promotes galvanic corrosion. Thus, a galvanic coupling was observed between the NdNiMg 15 phase (cathode) and the Mg phase (anode). An acceleration of the corrosion rate of Mg phase was observed due to this galvanic coupling. Electrochemical tests confirm that pure Mg has a corrosion rate in salt water up to 750 times lower than that of the Mg phase in the Mg NdNiMg 15 90% composite. The best hydrolysis performance (100% of the theoretical hydrogen generation yield in slightly more than 15 min) observed for Mg NdNiMg 15 90% composite, was explained by a combined effect of galvanic corrosion, intergranular corrosion and pitting corrosion. Highlights • Hydrolysis of Mg NdNiMg 15 composites are studied in NaCl solution. • Galvanic coupling between NdNiMg 15 phase (cathode) and the Mg phase (anode) exists. • Corrosion rate of composite is 750 times higher than the one of pure Mg. • NdNiMg 15 promote the galvanic and intergranular corrosion. [ABSTRACT FROM AUTHOR]

This paper dedicated to investigation the effect of carbons (graphite and carbon fibers), transition metals (TM = Ni, Fe and Al) and oxides (Nb 2 O 5 and V 2 O 5 ) on Mg–H hydrolysis reaction in aqueous media (3.5 wt% NaCl). Mg – 10 wt% X (X = C, TM and oxides) mixtures were prepared by mechanical milling (1, 3 and 5 h). Mg – 10 wt% G mixtures show the best hydrolysis performance (95% of theoretical hydrogen generation yield in almost 3 min) in comparison to Mg – oxide and Mg – TM mixtures. In addition to the presence of micro-galvanic cells, particle size, MgH 2 content, density defects, fractures and cracking have an important influence on the hydrolysis reaction. Synergetic effect of carbons and transition metals has been studied for Mg – 5 wt% G – 5 wt% Ni mixture. Activation energies were calculated using Avrami–Erofeev model. An activation energy of 14.34 kJ/mol was found for Mg/G/Ni mixture which demonstrates the best hydrolysis behavior (95% of theoretical hydrogen generation yield within 2 min). Hydrogen generated from Mg–H hydrolysis reaction was fed directly to a single Proton Exchange Membrane Fuel Cell (PEMFC). At 0.15 A, the cell voltage exhibited a stable value of approximately 0.52 V for roughly 35 min. [ABSTRACT FROM AUTHOR]

Hydrolysis is an effective method for generating hydrogen from Mg alloy waste provided from the sacrificial anode industry. Mg alloy was ball milled under H 2 to enhance its hydrolysis reactivity. The effect of ball milling time, the nature of the additives (graphite and AlCl 3) and the synergetic effect by chronological or simultaneous addition of 5 wt.% graphite and 5 wt.% AlCl 3 were examined. It has been established that increasing milling time without additive beyond 2 hours (h) decreases the hydrolysis performance. Using AlCl 3 slightly improves the hydrogen production properties when milling for 2 h. Incorporating graphite leads to the best hydrolysis properties (yield of 78% reached in 5 minutes when milled for 5 h). On the other hand, by combining both additives better results are obtained. The mixture prepared by milling for 2 h with 5 wt.% of graphite followed by additional milling for 2 h with 5 wt.% of AlCl 3 shows the best hydrolysis performance with a yield of 92% achieved in 5 minutes. When both additives are incorporated, the simultaneous or sequential addition and the order of incorporation strongly affect the microstructure and the morphology, and consequently the hydrogen production performance of the powders. • Mg alloy waste milled under H 2 produces H 2 by hydrolysis in 0.6 M MgCl 2 solution. • MgH 2 formed by BM increases the total H 2 production but reduces the performance. • Best hydrolysis performance obtained by BM with C(G) followed by BM with AlCl 3. [ABSTRACT FROM AUTHOR]