Hydrogen weakly bound

Figure 4. The structure and orientation of (a) weakly bound hydrogen and its associated water on a Pt or Rh electrode (b) water on the electrode surface at potentials in the double layer region.

Chandra, A. K., Nguyen, M. T., 1998, A Density Functional Study of Weakly Bound Hydrogen Bonded Complexes , Chem. Phys., 232, 299. 

Figure3.4 (a) Experimental l-E curve obtained at 0 C and curves computed from the assumption of a Langmuir isotherm, a = experimental curve b = partial curve for the strongly bound hydrogen, c = partial curve Tor the weakly bound hydrogen, d = computed net curve, (b) Experimental l - E curve obtained at 70 C and curves computed from the assumption of a Frumkin isotherm, a = experimental curve b = partial curve for the strongly bound hydrogen, c = partial curve for the weakly bound hydrogen, d = computed net curve. After Breiter(1964).

The potential at which the Pt-H stretch appeared, and the correlation between its subsequent increase in intensity and the rise in the cathodic hydrogen evolution current, is extremely strong evidence that this form of Had9 is the intermediate in the H2-evolution reaction as studied by Schuldiner (1959). This resolved the paradox between the kinetic results and the electrochemical measurements since Bowden. Clearly, the on-top hydrogen is only present at extremely low coverage, presumably on active sites. The strongly and weakly bound hydrogen play no part in the reaction. 

FIGURE 6. Two isomers (a and b) of the weakly bound hydrogen-bonded OH ONO optimized at the UB3LYP/6-31H-G(d,p) level of theory... 

Alkylperoxy radicals, being relatively stable and unreactive, are quite selective and preferentially abstract the most weakly bound hydrogen. The selectivity of... 

Incorporation of rhodium into the system results in the reduction of the adsorption maximum related to the strongly bonded hydrogen already at 40 at % of Rh it degenerates into a shoulder. With further increase of rhodium concentration in the alloy, it practically disappears. At the same time, the current corresponding to the weakly bound hydrogen adsorption slightly increases. The position of the adsorption maximum shifts towards the anode side along the potential scale up to the value of = 0.090 V, typical for the Rh-electrode [3]. 

If the potential of the adsorption maximum of the weakly bound hydrogen is plotted on the ordinate axis, and the composition of the binary Ir-Rh system is plotted on the abscissa axis, then practically a linear dependence between these values can be traced (Figure 3). 

Cr porphyrin complexes react with O2 to form stable oxochromium(IV) species. Por example, the red [(TPP)CrO] contains a five-coordinate Cr displaced out of the porphyrin plane toward the oxygen atom (Cr-O, 157.2pm). There are also a few Cr scorpionates featuring terminally bound 0x0 ligands. The most recent of these is paramagnetic [Tp Cr(pz H)(0)]BARP (Cr-O, 160.2pm), which abstracts weakly bound hydrogen atoms from hydrocarbons. ... 

Spectroscopic techniques nicely compliment synthesis and capacity work. One paper reviewed recent work on neutron powder diffraction, where MOFs loaded with different deuterium pressure were studied to directly pin point the location of hydrogen in these porous systems. For the first time the absorbed hydrogen molecules were located in the organic linker, and this highlights then-importance. It would be interesting to test this approach on the other systems that store weakly bound hydrogen. 

Here the bisulfite radical is oxidized by O2 to a peroxybisulfate radical which is reduced by NO to a bisulfate radical. The H-R molecule is some species such as H2O2 or HO2 with a relatively weakly bound hydrogen. 

Based upon the Bom-Oppenheimer separation of electronic and nuclear energies, the B-0 potential sinface should be isotopically invariant and the stmcture of a molecule should also be isotopically invariant. Most of the ti tly bound molecules of interest to chemists conform very well to the B-0 approximation, although all molecules deviate when examined at sufficient precision. Weakly bound hydrogen-bonded species or van der Waals molecules such as Ar—HCl are exceptions that require special considerations [3]. 

At least five types of hydrogen adsorption states on platinum electrodes have been postulated. These are the so-called strongly bound hydrogen, the weakly bound hydrogen, the on-top hydrogen, the dihydride state, and the sub-surface state. Most of these can be detected by cyclic voltammetry and characterized at single crystal electrodes [37-42]. 

Adsorption bands from the complex between water and weakly bound hydrogen (after ref. 55)... 

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