Hydrogen dissolution

Supramaniam Srinivasan began his career as a customs officer in Sri Lanka, but came in 1960 to the University of Pennsylvania where he wrote a Ph.D. thesis on a new way to determine the path of the hydrogen dissolution reactions on electrodes. Several of his further contributions to the fundamental basis of fuel cells are described in our text. 

A FIRST-PRINCIPLES STUDY OF HYDROGEN DISSOLUTION IN VARIOUS METALS AND PALLADIUM-SILVER ALLOYS... 

In the present study, we have applied first-principles calculations to study of the interaction of the dissolved hydrogen with various metals and alloys. Our computations have focused on the heat of hydrogen dissolution, which should be directly related to the solubility of hydrogen. 

The heat of hydrogen dissolution was calculated according to the following expression,... 

Heat of Hydrogen Dissolution. Figure 5 shows E ,ss for the fee metals. As for Ni and Pd, the O-site occupation was found to be more stable than the T-site occupation, whereas the T-site occupation was found to be more stable for Pt, Cu, Ag and Au. 

To study the effects of alloying of Pd with Ag on the heat of hydrogen dissolution, /(1 SS for the Pd/Ag alloy was evaluated in the same manner. Figure 7 illustrates the periodic supercell models for the Pd/Ag alloy. These models consist of three Pd atoms, one Ag atom, and one hydrogen atom. There are two distinguishable O-sites in these models one is the center of the octahedron consisting of four Pd atoms and two Ag atoms (Oa-site), and the other is the center of the octahedron consisting of six Pd atoms (Op-site). 

Lattice Expansion of Pure Metals by Hydrogen Dissolution... 

As the experimental heat of hydrogen dissolution (AHs),n plotted on Figure 5 and Figure 6, was obtained by applying Sieverts s law, the values may have some errors in high... 

We focus on dissociative hydrogen adsorption, hydrogen dissolution, and palladium hydride formation (68). Figure 28 provides a comparison of H2-TDS spectra... 

The selective occupation of interstitial sites implies that the atoms in an alloy retain some individuality. This is a feature which has long been recognized as important in surface reactions on alloys, but it is a much more recent observation in respect of bulk properties. Certainly in the case of hydrogen dissolution in a wide range of alloys of Pd with transition or non-transition metal partners the H seems to be capable of differentiating between the metal atoms. 

Fig.6. Bond orders between Ni and H atoms and between M and H atoms in the HM Ni cluster, and comparison with the heat of hydride formation of M metal or heat of hydrogen dissolution in M metal.

Table V gives the change in the heat of adsorption with potential and coverage for polycrystalline Pt and Pd. While AHa varies with coverage on Pt as expected, it remains relatively constant on Pd for d < 0.4. This may result from firmly adsorbed hydrogen or hydrogen dissolution in the palladium lattice (104).

The equilibrium potential of the electron electrode calculated in somewhat differs from the earlier data (cited, e.g., in ) since allowance was made for the energy of atomic hydrogen dissolution in water. Note, that the original paper > contains an erratum the true value of the equilibrium potential given above was recalculated from the hydration energy of the electron (see also... 

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