Morphology their stability

One of the main problems in the development of air gas-diffusion electrodes for metal-air cells is to find active and stable catalysts for the electrochemical reduction of oxygen. Carbon-based catalysts are mostly used, because of their highly developed surface area and capability for adsorption of 02, suitable morphology, chemical stability, good electric conductivity and comparatively low price. 

In the phase-space treatment the situation is very similar. However, rather than study the morphology of the potential energy surface, we must focus on the total energy surface. The geometry of this surface, which is defined on phase space instead of coordinate space, can also be characterized by its stationary points and their stability. In this treatment, the rank-one saddles play a fundamental result. They are, in essence, the traffic barriers in phase space. For example, if two states approach such a point and one passes on one side and the other passes on the other side, then one will be reactive and the other nonreactive. Once the stationary points are identified, then the boundaries between the reactive and nonreactive states can be constructed and the dynamical structure of phase space has been determined. As in the case of potential energy surfaces, saddles with rank greater than one occur, especially in systems with high symmetry between outcomes, as in the dissociation of ozone. 

In an effort to probe catalytic sites and their stability, the zeolite catalyst, ZSM-5 was Investigated by impedance and fourier transform infrared spectroscopies as a function of aluminium substitution and cation exchange. Samples were provided by Chemistry Division, DSIR, with (Si + A1)/A1 ratios of ao, 1000, 500, 200, 136 and 40. Crystallite size and morphology varied somewhat with aluminium content but typically the samples had crystal size distributions in the range 0.2 pus to 2 (im. 

Regarding the catalyst morphology, as discussed previously, there are varieties of catalyst shapes such as sphere, nanorod, nanofiber, nanotubing, core—shell, etc. For catalyst support, there are also different shapes similar to those of catalyst. Obviously, different combinations between different shape of catalyst and support could result in different ORR catalytic activities and stabilities. Normally, Pt-alloy catalysts with core—shell morphology could give the best ORR activities but their stabilities are questionable. The high ORR activity of Pt-alloy catalysts is... 

Small amounts of Ru or Ir were sputter-deposited on Pt-NSTF substrate to determine their stability and OER activity in a fuel cell environment. Ex situ characterization of as-grown material was first performed in order to characterize the morphology and surface state of each OER catalyst. Scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS) were employed to complete this task. Two different OER catalyst loadings were studied, 2 and 10 pg/cm, in order to explore the impact of layer thickness on the catalyst morphology and composition. 

It is important to characterize polymeric nanoassemblies to obtain informations such as their stability, size, and morphology. Many parameters such as the CMC (indicating... 

For poly(cu-(3-thienyl)alkanesulfonates), reported studies have been relatively sparse, but from those studies, many questions concerning these materials have emerged. For example, there is no information on how the regiochemistry of these polymers affects their physical properties. A full understanding of these materials requires more information on the correlation between morphology, conductivity, stability, and other physical attributes on the chemical structure and configuration. Compared to their non-sulfonated analogs, the poly(3-alkylthiophenes), we know little. 

Cheronov, A.A., and T. Nishinaga, 1987, Growth shapes and their stability at anisotropic interface kinetics theoretical aspects for solution growth, in Morphology of Crystals, ed. I. Sunagawa (Terrapub, Tokyo) ch. 3, pp. 207-267. 

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