Chemical equilibrium analysis for hydrolysis of magnesium hydride to generate hydrogen

Magnesium hydride is a promising hydrogen source because of its high mass density of hydrogen, 15.2%, when it is hydrolyzed; MgH₂ + 2H₂O = Mg(OH)₂ + 2H₂ + 277 kJ. However, a magnesium hydroxide, Mg(OH)₂, layer forms rapidly on the surface of the unreacted MgH₂ as the pH increases, hindering further reaction. The purpose of this study is to find acids that could effectively accelerate the reaction by using a chemical equilibrium analysis where the relationships of pH to concentration of ionized Mg were calculated. For the best performing acid, the calculated and measured relationships were compared, and the effects of acid concentration on hydrogen release were measured. The analysis revealed that citric acid and ethylenediamine-tetraacetic acid were good buffering agents. The calculated and measured relationships between pH and concentration of ionized Mg were in good accord. Hydrogen release improved considerably in a relatively dilute citric acid solution instead of pure distilled water. The maximum amount of hydrogen generated was 1.7 × 10³ cm³ g⁻¹ at STP after 30 min. We estimated the exact concentration of citric acid solution for complete MgH₂ hydrolysis by a chemical equilibrium analysis method.     

SANS studies on catalyst ink of fuel cell

The structure of solid polymer electrode and catalyst ink of fuel cell has been investigated by focusing‐ (FSANS) and contrast‐variation small‐angle neutron scattering (CV‐SANS). The solid polymer electrode, consisting of carbon (C), platinum, and ionomer (polymer, P), exhibited a power‐law function with two asymptotes, i.e., from I(q) ～ q^?1 to I(q) ～ q^?4 with a crossover around q ≈ 0.005 Å^?1. The scattering functions of the catalyst ink, i.e., the polymer electrodes dispersed in water, were successfully decomposed to the corresponding partial structure factors, S_CC(q), S_PP(q), S_CP(q), exclusively representing C‐C, P‐P, and C‐P correlations. S_CC(q) was a monotonic decreasing function of q, dominating in the scattering from carbon clusters. On the other hand, S_PP(q) exhibited a scattering maximum characteristic of polyelectrolyte solutions. This suggests that ionic clusters in polyelectrolyte solutions are formed in catalyst ink. The cross term, S_CP(q), indicated that the carbon scattering is dominant and significant amount of ionomer is adsorbed on the carbon agglomerates. It is concluded that the catalyst ink consists of carbon agglomerates surrounded by ionomers and the presence of ionic‐cluster path plays a key role in the performance of the solid polymer electrodes in polymer electrolyte fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39842.     

13C CP/MAS NMR study of accommodation of various organic molecules in (±)-[Co(en)3]Cl3 ionic crystal and their local structure

Accommodation of various organic molecules into a one-dimensional nanochannel of tris(ethylenediamine) cobalt(III) chloride, [Co(en)₃]Cl₃, anhydrated racemic crystal was examined using weight increment measurements, thermogravimetric–differential thermal analysis (TG–DTA), powder X-ray diffraction (PXRD) and ¹³C cross-polarization/magic angle sample spinning (CP/MAS) NMR techniques. Results showed that the (±)-[Co(en)₃]Cl₃ ionic crystal accommodates n-alkanes, n-alkylalcohols, n-alkylamines, and acetonitrile in the 1D nanochannel without decomposition of the crystal lattice. The guest molecules are in all-trans conformation in the nanochannel. Furthermore, the activation energies of uni-axial molecular reorientation of n-alkanes and n-alkylalcohols in the nanochannel were determined using temperature dependence of the ¹H spin–lattice relaxation time in the rotating frame (T_1ρ). Results demonstrated that the activation energy per CH₂ unit (6.5 kJ mol^?1) in n-alkylalcohols was twice that in n-alkanes (3.3 kJ mol^?1), implying the possibility of dimer formation of n-alkylalcohols in the nanochannel by hydrogen bonding through OH group. These findings strongly suggest that the (±)-[Co(en)₃]Cl₃ ionic crystal has adsorption ability to various organic molecules. It will open new avenues to explore new types of zeolites that include ionic crystals.     

An Information-Spectrum Approach to Classical and Quantum Hypothesis Testing for Simple Hypotheses

The information-spectrum analysis made by Han for classical hypothesis testing for simple hypotheses is extended to a unifying framework including both classical and quantum hypothesis testing. The results are also applied to fixed-length source coding when loosening the normalizing condition for probability distributions and for quantum states. We establish general formulas for several quantities relating to the asymptotic optimality of tests/codes in terms of classical and quantum information spectra     

Polarization reversal of telluric acid ammonium phosphate

Experimental studies are reported concerning polarization reversal in the single crystal of telluric acid ammonium phosphate (TAAP). The switching currents have been measured under various temperatures and external electric fields. The experimental results have been used in order to obtain the effective growth dimension of reversed domain and the characteristic time of the polarization reversal on the basis of the Avrami theory. It becomes clear that the effective growth dimension depends on temperature and applied electric field.     

Preparation and characterization of active Ni/MgO in oxidative steam reforming of n-C4H10

Oxidative steam reforming of n-C₄H₁₀ over MgO-supported Ni catalysts is described. The Ni/MgO catalysts were prepared by the impregnation method from aqueous Ni(NO₃)₂ precursor solutions at two pH values. Ni/MgO prepared at pH 7 exhibited considerably higher activity than Ni/MgO prepared from a conventional acidic aqueous precursor solution (pH 3.5). The H₂ formation rate for the modified Ni/MgO was up to 2.3 times that for conventional Ni/MgO under a high space velocity of 1660 L(h g)⁻¹. Furthermore, after reduction at high temperature (1273 K), the modified Ni/MgO showed a higher H₂ formation rate than did Rh/MgO. The superior performance of the modified Ni/MgO was ascribed to stronger resistance to oxidation of Ni⁰ due to the formation of relatively large Ni⁰ particles.