Synthesis and electrochemical properties of binary MgTi and ternary MgTiX (X = Ni, Si) hydrogen storage alloys

Mg-based hydrogen storage alloys are promising candidates for many hydrogen storage applications because of the high gravimetric hydrogen storage capacity and favourable (de)hydrogenation kinetics. In the present study we have investigated the synthesis and electrochemical hydrogen storage properties of metastable binary MgyTi1−y (y = 0.80–0.60) and ternary Mg0.63Ti0.27X0.10 (X = Ni and Si) alloys. The preparation of crystalline, single-phase, materials has been accomplished by means of mechanical alloying under controlled atmospheric conditions. Electrodes made of ball-milled Mg0.80Ti0.20 powders show a reduced hydrogen storage capacity in comparison to thin films with the same composition. Interestingly, for a Ti content lower than 30 at.% the reversible storage capacity increases with increasing Ti content to reach a maximum at Mg0.70Ti0.30. The charge transfer coefficients (α) and the rate constants (K1 and K2) of the electrochemical (de)hydrogenation reaction have been obtained, using a theoretical model relating the equilibrium hydrogen pressure, electrochemically determined by Galvanostatic Intermittent Titration Technique (GITT), and the exchange current. The simulation results reveal improved values for Mg0.65Ti0.35 compared to those of Mg0.80Ti0.20. The addition of Ni even more positively affects the hydrogenation kinetics as is evident from the increase in exchange current and, consequently, the significant overpotential decrease

Influence of nickel and silicon addition on the deuterium siting and mobility in fcc Mg-Ti hydride studied with 2H MAS NMR.

Fluorite-structured Mg–Ti hydrides are interesting for hydrogen storage applications because of their high gravimetric hydrogen storage capacity, and improved (de)hydrogenation kinetics compared to MgH2. In the present study we have investigated the potential catalytic effect of Ni and Si as third element on the siting and mobility of electrochemically loaded deuterium in ball-milled Mg0.63Ti0.27Ni0.10 and Mg0.63Ti0.27Si0.10 alloys. Magic angle spinning (MAS) 2H NMR reveals that Ni and Si induce new types of deuterium sites in addition to the Mg-rich and Ti-rich sites already present in Mg0.65Ti0.35D1.2. 2D exchange NMR spectroscopy shows a substantial deuterium exchange between the various types of sites, which reflects their close interconnectivity in the crystal structure. Furthermore, the time scale and temperature dependence of the deuterium mobility have been quantified by 1D exchange NMR. The obtained effective residence times for deuterium atoms in the Mg-rich and Ti-rich nanodomains in Mg0.65Ti0.35D1.2, Mg0.63Ti0.27Ni0.10D1.3, and Mg0.63Ti0.27Si0.10D1.1 at 300 K are 0.4, 0.3, and 0.8 s, respectively, and the respective apparent activation energies 17, 21, and 27 kJ mol–1. The addition of Ni promotes deuterium mobility inside Mg–Ti hydrides, which is in agreement with the observed catalytic effect of Ni on the electrochemical (de)hydrogenation of these materials

Influence of Nickel and Silicon Addition on the Deuterium Siting and Mobility in fcc Mg–Ti Hydride Studied with ²H MAS NMR

Fluorite-structured Mg–Ti hydrides are interesting for hydrogen storage applications because of their high gravimetric hydrogen storage capacity, and improved (de)­hydrogenation kinetics compared to MgH₂. In the present study we have investigated the potential catalytic effect of Ni and Si as third element on the siting and mobility of electrochemically loaded deuterium in ball-milled Mg_0.63Ti_0.27Ni_0.10 and Mg_0.63Ti_0.27Si_0.10 alloys. Magic angle spinning (MAS) ²H NMR reveals that Ni and Si induce new types of deuterium sites in addition to the Mg-rich and Ti-rich sites already present in Mg_0.65Ti_0.35D_1.2. 2D exchange NMR spectroscopy shows a substantial deuterium exchange between the various types of sites, which reflects their close interconnectivity in the crystal structure. Furthermore, the time scale and temperature dependence of the deuterium mobility have been quantified by 1D exchange NMR. The obtained effective residence times for deuterium atoms in the Mg-rich and Ti-rich nanodomains in Mg_0.65Ti_0.35D_1.2, Mg_0.63Ti_0.27Ni_0.10D_1.3, and Mg_0.63Ti_0.27Si_0.10D_1.1 at 300 K are 0.4, 0.3, and 0.8 s, respectively, and the respective apparent activation energies 17, 21, and 27 kJ mol^–1. The addition of Ni promotes deuterium mobility inside Mg–Ti hydrides, which is in agreement with the observed catalytic effect of Ni on the electrochemical (de)­hydrogenation of these materials

Recurrent <em>EZH1 </em>mutations are a second hit in autonomous thyroid adenomas.

Autonomous thyroid adenomas (ATAs) are a frequent cause of hyperthyroidism. Mutations in the genes encoding the TSH receptor (TSHR) or the Gs protein &alpha; subunit (GNAS) are found in approximately 70% of ATAs. The involvement of other genes and the pathogenesis of the remaining cases are presently unknown. Here, we performed whole-exome sequencing in 19 ATAs that were paired with normal DNA samples and identified a recurrent hot-spot mutation (c.1712A&gt;G; p.Gln571Arg) in the enhancer of zeste homolog 1 (EZH1) gene, which codes for a catalytic subunit of the polycomb complex. Targeted screening in an independent cohort confirmed that this mutation occurs with high frequency (27%) in ATAs. EZH1 mutations were strongly associated with known (TSHR, GNAS) or presumed (adenylate cyclase 9 [ADCY9]) alterations in cAMP pathway genes. Furthermore, functional studies revealed that the p.Gln571Arg EZH1 mutation caused increased histone H3 trimethylation and increased proliferation of thyroid cells. In summary, this study revealed that a hot-spot mutation in EZH1 is the second most frequent genetic alteration in ATAs. The association between EZH1 and TSHR mutations suggests a 2-hit model for the pathogenesis of these tumors, whereby constitutive activation of the cAMP pathway and EZH1 mutations cooperate to induce the hyperproliferation of thyroid cells