Hydrolysis Of Mg Research Articles

Microstructure and improved hydrogen generation performance via hydrolysis of Mg–Ca alloys with TiC and Ni addition

Mg-xCa (x = 3, 7, 11, 14, wt.%) binary hypoeutectic alloys are successfully synthesized via solidification in the present work. The microstructure, phase compositions and hydrogen generation characteristics of as-cast Mg–Ca alloys and ball milled Mg–Ca composites with TiC and Ni addition have been investigated in this work for a new hydrogen supply source application. A lamellar structure with alternately distributed Mg and Mg2Ca is formed in the eutectic regions of as-cast Mg–Ca binary alloys. It is found that as-cast Mg–Ca binary alloys show extremely sluggish hydrolysis kinetics and low hydrogen yield in both tap water and simulated seawater. Mg2Ca phase preferentially reacts with water during hydrolysis process in simulated seawater. Many cracks arise with hydrolysis reaction, meanwhile, the cracks further assist in the hydrolysis of the internal matrix via assisting water solution transfer. After ball milling with TiC and Ni of Mg–Ca binary alloys, the hydrolysis performance is substantially modified. Mg–14Ca-3wt.%TiC-5wt.%Ni composite generates 836.6 mL g−1 of hydrogen within initial 95 min. The conversion rate of Mg–14Ca-3wt.%TiC-5wt.%Ni composite in simulated seawater is as high as 99.4%, indicating a thorough hydrolysis of Mg and Mg2Ca phases with the catalysis of TiC and Ni. This work shows that microstructure refinement, catalysis, Mg(OH)2 exfoliation and water solution transfer account for the complete hydrolysis.

Carbon nano-tube coated with iron carbide catalysis for hydrolysis of magnesium to generate hydrogen

Hydrolysis of magnesium (Mg) or their composites are considered as an efficient, economical and enabling technique to produce hydrogen (H2). In this study, carbon nano-tube coated with iron carbide (CNT@Fe3C) was synthesized and applied as a catalyst to promote hydrolysis of Mg to generate H2. Ball milling technique was employed to prepare Mg-Xwt%CNT@Fe3C (X = 0.2, 2.0, 5.0 and 10.0) composites for hydrolysis in seawater. Among employed composites, the results demonstrated that the introduction of small amount of CNT@Fe3C promote the hydrolysis kinetics of Mg. Particularly, Mg-5.0 wt%CNT@Fe3C composite ball milled for 1 h released 866.5 mL/g H2 with 10072.0 mLg−1min−1 initial hydrogen generation rate mHGR and demonstrated an excellent composite. Furthermore, activation energy of Mg hydrolysis kinetic dropped to 23.6 kJ/mol. Hence, CNT@Fe3C inhibited the magnesium hydroxide (Mg(OH)2) from sticking to the unreacted Mg surfaces, which enhanced its galvanic corrosion and reactivity. In order to develop portable H2 generators, CNT@Fe3C supported Mg system can provide clean H2 to reduce the adverse environmental effect.

Tailoring of Hydrogen Generation by Hydrolysis of Magnesium Hydride in Organic Acids Solutions and Development of Generator of the Pressurised H2 Based on this Process

Hydrolysis of light metals and hydrides can potentially be used for the generation of hydrogen on-board fuel cell vehicles, or, alternatively, for refilling their fuel tanks with H2 generated and pressurised without compressor on site, at near-ambient conditions. Implementation of this approach requires solution of several problems, including the possibility of controlling H2 release and avoiding thermal runaway. We have solved this problem by developing the apparatus for the controlled generation of pressurised H2 using hydrolysis of Mg or MgH2 in organic acid solutions. The development is based on the results of experimental studies of MgH2 hydrolysis in dilute aqueous solutions of acetic, citric, and oxalic acids. It was shown that the hydrogen yield approaches 100% with a fast hydrolysis rate when the molar ratio acid/MgH2 exceeds 0.9, 2.0, and 2.7 for the citric, oxalic, and acetic acids, respectively. In doing so, the pH of the reaction solutions after hydrolysis corresponds to 4.53, 2.11, and 4.28, accordingly, testifying to the buffer nature of the solutions “citric acid/magnesium citrate” and “acetic acid/magnesium acetate”. We also overview testing results of the developed apparatus where the process rate is effectively controlled by the control of the acid concentration in the hydrolysis reactor.

Effective hydrogen production by hydrolysis of Mg wastes reprocessed by mechanical milling with iron and graphite

Effective hydrogen production by hydrolysis of Mg wastes reprocessed by mechanical milling with iron and graphite

A reusable dual functional Mo2C catalyst for rapid hydrogen evolution by Mg hydrolysis

A Mg–Mo2C composite is prepared with excellent hydrogen generation properties by hydrolysis. During Mg hydrolysis, Mo2C enhances the self-hydrolysis of Mg and induces the electrochemical hydrolysis of Mg using its high HER catalytic activity.

Conversion coating technology for recovery and reuse of waste Mg alloy polishing powder

The waste dust from Mg alloy grinding not only has the danger of explosion, but also reduces the performance of Mg due to the oxidation and hydrolysis of Mg, which seriously limits the reuse of Mg alloy waste dust. In order to avoid the oxidation of Mg alloy dust and recycle it, four inerting agents, including sodium citrate and sodium alginate, were selected to inertize waste Mg alloy dust. The results show that when used alone, none of the inerting agents can completely prevent the production of Mg(OH)2. After the combination of organic sodium citrate and inorganic sodium silicate, the inerting efficiency of Mg alloy dust can reach 99.4%, which is more than 20% higher than that of any inerting agent used alone. XRD and FTIR results showed that a composite conversion film composed of [SC-Mg] and hydrated magnesium silicate is formed on the surface of waste Mg alloy dust particles, which blocks the contact between external water molecules and Mg2+ ions. Stability test under different conditions showed that the composite conversion film can maintain good stability under different temperatures, disturbance speeds and Cl− concentrations. The inerted Mg alloy dust (0.4 wt% SC+0.2 wt% SS) has been verified in industrial application, and the reuse possibility of residual Mg alloy powder has been confirmed. This study not only provides a simple and effective method for recycling waste Mg alloy dust, but also reduces the explosion risk during dust collection and transportation.

Enhanced hydrogen generation via hydrolysis of Mg–Mg2NiH4 system

Producing hydrogen via hydrolysis of light weighted metal-based materials is a promising technology for exploiting portable hydrogen–air fuel cells. Various additives have been designed to catalyze the hydrolysis behavior of Mg-based materials. In most cases, however, the kinetic promotion is in the expense of the systematic hydrogen generation yield. In this work, Mg–Mg2NiH4 system with extraordinary hydrolysis property is explored for hydrogen generation in 3.5% NaCl aqueous solution for the first time. The Mg-10 wt% Mg2NiH4 composite releases 845.1 mL g−1 (yield of 94.7%) hydrogen in just 20 s, with a maximum hydrogen generation rate (mHGR) of 6391 mL g−1 min−1. Our results have experimentally shown the synergistic effect between Mg and Mg2NiH4 on hydrolysis reaction. The in-situ ultrafine Ni particles derived from the rapid hydrolysis of Mg2NiH4 form a large amount of micro-galvanic cells with Mg, accelerating the electrochemical corrosion of Mg efficiently. In turn, the hydrolysis reaction of Mg2NiH4 can be dramatically driven by the local solution heat due to the violent exothermic reaction of Mg. The cooperative effect provides fresh strategy designing high-property hydrolysis materials with no substantial loss of the hydrogen supply capacity.

Hydrolysis of Mg(BH4)2 and its coordination compounds as a way to obtain hydrogen

Three ligand-stabilized Mg(BH4)2–based complexes have been synthesized and evaluated as potential hydrogen storage media for portable fuel cell applications. The new borohydrides: Mg(BH4)2 × 0.5Et2O and Mg(BH4)2 × diglyme (diglyme – CH3O(CH2)2O(CH2)2OCH3) have been synthesized and examined by X-ray single crystal diffraction method. Hydrolysis reactions of the compounds liberate hydrogen in quantities ranging from 46 to 96% of the theoretical yield. The hydrolysis of Mg(BH4)2 and other borohydrides is also accompanied by the diborane formation. The amount of liberated diborane depends on the Mg-coordination environment. To explain this fact quantum-chemical calculations have been performed. It is shown that formation of Mg-O-Mg-bridges enables the side process of diborane generation. It means that the size and denticity of the ligand directly affects the amount of released diborane. In general, the larger the ligand and the higher its denticity, the smaller is amount of diborane produced. The new compound Mg(BH4)2 × diglyme decomposes without diborane formation that allows one to be considered as a new promising chemical hydrogen storage compound for the practical usage.

Enhanced hydrogen generation by hydrolysis of Mg doped with flower-like MoS2 for fuel cell applications

In this work, flower-like MoS2 spheres are synthesized via a hydrothermal method and the catalytic activity of the as-prepared and bulk MoS2 on hydrolysis of Mg is systematically investigated for the first time. The Mg-MoS2 composites are prepared by ball milling and the hydrogen generation performances of the composites are investigated in 3.5% NaCl solution. The experimental results suggest that the as-prepared MoS2 exhibits better catalytic effect on hydrolysis of Mg compared to bulk MoS2. In particular, Mg-10 wt% MoS2 (as-prepared) composite milled for 1 h shows the best hydrogen generation properties and releases 90.4% of theoretical hydrogen generation capacity within 1 min at room temperature. The excellent catalytic effect of as-prepared MoS2 may be attributed to the following aspects: three-dimensional flower-like MoS2 architectures improve its dispersibility on Mg particles; make the composite more reactive; hamper the generated Mg(OH)2 from adhering to the surface of Mg; and increase the galvanic corrosion of Mg. In addition, a hydrogen generator based on the hydrolysis reaction of Mg-0.2 wt% MoS2 composite is manufactured and it can supply a maximum hydrogen flow rate of 2.5 L/min. The findings here demonstrate the as-prepared flower-like MoS2 can be a promising catalyst for hydrogen generation from Mg.

High-temperature hydrolysis of magnesium nitrate hexahydrate

The high-temperature hydrolysis of magnesium nitrate hexahydrate is studied. The presence of basic magnesium nitrate in the decomposition product at 160°C is found by IR spectroscopy and X-ray diffraction analysis. A mechanism for the high-temperature hydrolysis of Mg(NO3)2 · 6H2O is proposed.

Hydrogen generation via hydrolysis of magnesium with seawater using Mo, MoO2, MoO3 and MoS2 as catalysts

MoS2 could significantly enhance the hydrolysis of Mg and the recycled MoS2 catalyst exhibited high recycling stability.

Fabrication of Mg–Ni–Sn alloys for fast hydrogen generation in seawater

Mg-2.7Ni-x wt.% Sn(x = 0–2) alloys were fabricated to promote hydrogen generation kinetics of Mg-2.7Ni alloy. The Sn in Mg-2.7Ni-Sn alloys exists as Mg2Sn phase at the grain boundary and solid solution at the Mg matrix. The Mg2Sn at the grain boundary acts as the initiation site for pitting corrosion and the dissolved Sn in the alloy causes pitting corrosion by locally breaking the surface oxide film in the Mg matrix in seawater. The Mg-2.7Ni-1Sn alloy showed an excellent hydrogen generation rate of 28.71 ml min−1 g−1, which is 1700 times faster than that of pure Mg due to the combined action of galvanic and intergranular corrosion as well as pitting corrosion in seawater. As the solution temperature was increased from 30 to 70 °C, the hydrogen generation rate from the hydrolysis of the Mg-2.7Ni-1Sn alloy was dramatically increased from 34 to 257.3 ml min−1 g−1. The activation energy for the hydrolysis of Mg was calculated to be 43.13 kJ mol−1.

Design of Mg–Ni alloys for fast hydrogen generation from seawater and their application in polymer electrolyte membrane fuel cells

Mg and its alloys are very attractive for hydrogen generation via hydrolysis because their hydrolysis reaction occurs in neutral seawater instead of the alkaline water necessary for the hydrolysis of Al and its alloys. The hydrogen generation rate from the hydrolysis of Mg is proportional to the corrosion rate of Mg to Mg2+. Mg powder, though producing a high reaction rate in the hydrolysis, causes explosive dangers when in contact with air or moisture. However, Bulk Mg such as plate and sheet exhibits an extremely low hydrogen generation rate. To overcome the disadvantage, Mg–Ni alloys were designed to form an electrochemically noble phase (Mg2Ni) along grain boundaries (G.B.), and hence to significantly accelerate the hydrolysis rate by causing a galvanic and intergranular corrosion between the noble Mg2Ni and Mg matrix. In particular, the Mg–2.7Ni alloy among the designed Mg–Ni alloys exhibits the highest hydrogen generation rate (23.8 ml min−1 g−1) that is 1300 times faster than that of pure Mg. Furthermore, it was demonstrated that PEMFC stably produced 7.3 W for 20 min when it is operated by the hydrogen generated from the hydrolysis of 2 g Mg–2.7Ni alloy, that is, equivalent to 1.215 KWh/Kg-Mg–2.7Ni alloy.

How the synthesis conditions and structure of the starting nanocrystalline powders affect the optical properties of transparent ceramic MgAl_2O_4

Nanocrystalline powders of aluminum–magnesium spinel synthesized by the hydrolysis of Mg–Al double isopropylate have been studied, micrographs of the samples have been obtained, and x-ray phase analysis has been carried out. Hot uniaxial pressing was used to fabricate ceramic samples that possess the highest transmittance in the IR region. It is established that the heating rate, temperature, and heat-treatment time when the nanopowders are synthesized affects their structural and morphological properties, as well as the optical properties of the ceramic made from them. The optimum conditions for synthesizing the powders is determined, and the transmission spectra of the ceramic samples are studied.

Carbon Nanotube/Magnesium Composite as a Hydrogen Source.

Hydrogen produced using the steam reforming process contains sulfur and carbon monoxide that are harmful to the Pt catalyst in proton-exchange-membrane fuel cells (PEMFCs). However, CO-free hydrogen can be generated from the hydrolysis of either Al in strongly alkaline water or Mg in neutral water with chlorides such as sea water. The hydrogen generation rate from the hydrolysis of Mg is extremely slow and linearly proportional to the corrosion rate of Mg in chloride water. In this work, we fabricated a carbon nanotube (CNT)--reinforced Mg--matrix composite by Spark Plasma Sintering as a fast hydrogen generation source for a PEMFC. The CNTs distributed in the Mg matrix act as numerous local cathodes, and hence cause severe galvanic corrosion between the Mg-matrix anode and CNT-cathode in NaCl solution. It was found that the hydrogen generation rate from the hydrolysis of the 5 vol.% CNT/Mg composite is 3300 times faster than that of the Mg without CNTs due primarily to the galvanic corrosion effect.

Hydrogen generation by the hydrolysis of magnesium–aluminum–iron material in aqueous solutions

Abstract Highly activated Mg–Al–Fe materials are prepared from powder by mechanical ball milling method for hydrogen generation. The hydrolysis characteristics of Mg–Al–Fe materials in aqueous solutions under different experimental conditions are carefully investigated. The results show that the hydrolysis reactivity of Mg–Al–Fe material can be significantly improved by increasing the ball milling time and Fe content. The increase of NaCl solution concentration and initial temperature is also found to promote the hydrogen generation reaction. At 25 °C, the Mg60–Al30–Fe10 (wt%) material ball-milled for 4 h shows the best performance in 0.6 mol L−1 NaCl solution, and the reaction can produce 1013.33 ml g−1 hydrogen with a maximum hydrogen generation rate of 499.50 ml min−1 g−1. In comparison to NaCl solution, natural seawater is found to have an inhibiting effect on the hydrolysis of Mg–Al–Fe material. Especially, the presence of Mg2+ and Ca2+ in seawater can greatly reduce the hydrogen conversion yield, and the SO42− can decrease the hydrogen generation rate.

Thickness-Dependent Hydroxylation of MgO(001) Thin Films

Hydroxylation of MgO surfaces has been studied from UHV to mbar pressure for MgO(001) films of different thickness grown on Ag(001) by X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and density functional theory calculations. In agreement with earlier studies on MgO(001) single crystals, a threshold water pressure on the order of 10−4 mbar is found for extensive hydroxylation of thick, bulklike MgO films. Decreasing the MgO film thickness shifts the threshold pressure to lower values, being 10−6 mbar in the limit of 2 monolayer MgO(001)/Ag(001). This result is explained on the basis of the precursor state of periclase MgO(001) dissolution involving hydrolysis of Mg−O surface bonds. The enhanced structural flexibility (polaronic distortion) of the ultrathin MgO film facilitates surface hydroxylation by lowering the barrier for hydrolysis.

The role played by pentacovalent intermediates in the sequence of stages of the hydrolysis of 5′-ATP with metal ions

The earlier developed model of irreversible hydrolysis of 5′-ATP catalyzed by the main metal ion Cu2+ was used to consider the influence of additional metal ions on the deactivation of active centers conjugated with hydrolysis. It was assumed that conjugation in enzymes occurred through a sequence of stages including the formation of pentacovalent intermediates at early hydrolysis stages and their subsequent slow pseudorotation with the participation of the γ phosphorus atom of the pentacovalent intermediate. From this standpoint, the formal kinetic laws of the hydrolysis of Mg·ATP were analyzed for two enzymes, luciferase from fireflies and nitrogenase Azotobacter vinelandii. The roles played by Mg2+ OH− ion formation with the participation of external OH− ions and the selective hydration of intermediate hydrolysis products by a coordinated water molecule of the second metal ion, including the transition metal ion participating in hydrolysis, were considered.

The effect of mixed surfactants of sodium dodecyl sulfate and Triton X-100 on the base hydrolysis of Malachite green

The base hydrolysis of Malachite green (MG+) was studied in aqueous solution of mixed surfactants of sodium dodecyl sulfate (SDS) and Triton X-100 (TX-100) at 25 °C. The results show that the SDS/TX-100 system compositions has relatively significant influence on the rate constant of the base hydrolysis of MG+ when compared with the reaction in the respective single surfactant systems.

The hydrolysis behaviour of Mg2Ni and Mg2NiH4 in water or a 6M KOH solution and its application to Ni nanoparticles synthesis

Abstract Both Mg 2 Ni and Mg 2 NiH 4 undergo hydrolysis in water and in a 6 M KOH alkaline solution. Mg 2 Ni spontaneously reacts with water to form Mg(OH) 2 , Ni and hydrogen. Mg 2 NiH 4 first dissociates into Mg 2 Ni and hydrogen, and then the Mg 2 Ni is further hydrolyzed into Mg(OH) 2 and Ni. The hydrolysis characteristics of both Mg 2 Ni and Mg 2 NiH 4 suggest that they are not suitable for use as electrodes in rechargeable batteries. After the Mg(OH) 2 in the hydrolysis product of Mg 2 Ni in distilled water was carefully removed using dilute hydrochloric acid, spherical Ni particles with a size of about 10 nm were obtained. The hydrolysis of Mg 2 Ni or Mg 2 NiH 4 therefore provides a new and relatively simple method for the production of nickel nanoparticles.