Shengtao Zhang

Induced effect of Mn3O4 on formation of MnO2 crystals favourable to catalysis of oxygen reduction

Catalysts prepared from a mixture of Mn3O4 powders and carbon blacks carrying pyrolytic MnO2 were investigated for catalysis of oxygen reduction. It was found that the introduction of Mn3O4 to the pyrolysis process of manganous nitrate carried out on carbon blacks improved the performance of air electrodes as the amount of Mn3O4 was controlled within 15 wt% relative to the weight of carbon carrier. The mechanism of this improved behaviour was also investigated using X-ray diffraction (XRD). The results showed that Mn3O4 induced the formation of favourable MnO2 crystalline grains during the pyrolysis of manganous nitrate. The induced effect and the blocking effect of Mn3O4 on the catalysis of air electrodes catalysed by pyrolytic MnO2 were demonstrated both on carbon black and porous carbon carriers.

Stabilization of platinized carbon catalysts for PAFC

In phosphoric acid fuel cells operating with oxygen and hydrogen it is well known that the activation overpotential for oxygen reduction at the cathode is far larger than that for hydrogen oxidation at the anode. This is because the exchange current density for the oxygen electrode is as low as 10 ˇ10 mA cm ˇ2 at room temperature, whereas that for the hydrogen electrode is as high as 10 ˇ4 mA cm ˇ2 . It is also the case that only a few metals are suitable for use as an electrode for oxygen reduction. This is because most metals and their alloys, except those of the platinum group, are not stable at the potential of oxygen reduction, especially in acidic electrolytes. Even when platinum group metals are used as cathodic materials, their corrosion and sintering tend to increase during cell operation. This can lead to reduction in the cell output and, hence, in the overall operational eAciency. With the objective of solving such problems, a wide variety of studies have been made on carbon-based electrodes carrying platinum with other metals, such as platinum‐vanadium [1], platinum‐chromum [2], platinum‐chromum‐cobalt [3], platinum‐palladium and platinum‐ruthenium [4, 5] and platinum‐ruthenium‐ niobium‐nickel [6]. None of these catalysts, however, is completely satisfactory. Some of them have a suAciently high initial activity, but they tend to lose activity over a relatively short time, and others maintain activity for a long time, but the level of activity is insuAcient. Work in the authors’ laboratories has shown that a platinum alloy with iron and/or cobalt can provide electrocatalysts free from the drawbacks mentioned above [7, 8].

A first-principles study on the structural, elastic, electronic, and optical properties of CdRh2O4

The structural, elastic, electronic, and optical properties of CdRh2O4 with cubic

Corrosion inhibition of mild steel in acidic solution by some oxo-triazole derivatives

(Fd\overline{ 3} m)

The effect of some triazole derivatives as inhibitors for the corrosion of mild steel in 1 M hydrochloric acid

(Fd3¯m) and orthorhombic (Pnma) structures have been investigated using a pseudopotential plane wave (PP-PW) method within the local density approximation (LDA). The calculated lattice parameters agree reasonably with the experimental values. The single-crystal elastic stiffness constants Cijs of the cubic and orthorhombic phases are investigated using the stress–strain method. In addition, the polycrystalline elastic properties including bulk modulus, shear modulus, Young’s modulus, bulk modulus–shear modulus ratio, Poisson’s ratio, and elastic anisotropy ratio are determined based on Voigt–Reuss–Hill approach. The use of the hybrid functional sX-LDA leads to considerably improved electronic properties compared to standard LDA approach. On the other hand, the dielectric function, refraction index, reflectivity, conductivity function, and energy-loss spectra were obtained and analyzed on the basis of electronic band structures and density of states.