Adsorption of molecular hydrogen

Adsorption of Reaction Components In many cases, adsorption of a reactant is one of the hrst steps in the electrochemical reaction, and precedes charge transfer and/or other steps of the reaction. In many cases, intermediate reaction products are also adsorbed on the electrode s snrface. Equally, the adsorption of reaction products is possible. The example of the adsorption of molecular hydrogen on platinum had been given earlier. Hydrogen adsorption is possible on the platinum electrode in aqueons solntions even when there is no molecular hydrogen in the initial system at potentials more negative than 0.3 V (RHE), the electrochemical reaction... 

The comparison of experimental data on adsorption of various particles on different adsorbents indicate that absorbate reaction capacity plays a substantial role in effects of influence of adsorption on electric conductivity of oxide semiconductors. For instance, the activation energy of adsorption of molecular oxygen on ZnO is about 8 kcal/mole [83] and molecular hydrogen - 30 kcal/mole [185]. Due to such high activation energy of adsorption of molecular hydrogen at temperatures of adsorbent lower than 100 C (in contrast to O2) practically does not influence the electric conductivity of oxides. The molecular nitrogen and... 

Highly exothermic adsorption of molecular hydrogen, oxygen and nitrogen into the atomic state on clean metals is virtually unactivated [Fig. 2(a) and (d)],so we can write for such systems E12 = — AU21. When— AU2, is less than Em, molecular adsorption is activated and, in such cases, we suppose that Ed is zero and then E 2 = Em [see Fig. 2(b) and (c)]. 

Chemisorption of hydrogen — Process leading to the formation of strongly bound (chemisorbed) hydrogen atoms on an adsorbent (mostly on metal) either via the dissociative adsorption of molecular hydrogen (H2) or, in the case of electrified interfaces, by charge transfer process occurring, for instance, with H+(H30+) or H20 species... 

TIius, at low coverage, dissociative adsorption leads to a dependence of 0 on the square root of the partial pressure of hydrogen, while adsorption of molecular hydrogen leads to a linear dependence of 0 on the pressure. The adsorption of molecular hydrogen was studied in this manner on catalytic metals, such as platinum, palladium and nickel and found to be dissociative, following Eq. 51. 

The mechanism for the HOR on a platinum electrode [84, 85] is usually assumed to proceed by the adsorption of molecular hydrogen, which involves... 

AreUano, J.S., Molina, L.M., Rubio, A., and Alonso,. A. (2000). Density functional study of adsorption of molecular hydrogen on graphene layers. J. Chem. Phys., 112, 8114-19. 

Adsorbed atomic hydrogen, most probably arising from the dissociative adsorption of molecular hydrogen on pairs of vacant sites. 

P.N. Jones, E. Knozinger, W. Langel., R.B. Moyes J. Tomkinson (1988). Surf. Sci., 207, 159-176. Adsorption of molecular-hydrogen at high-pressure and temperature on M0S2 and WS2 - observed by inelastic neutron-scattering. 

The adsorption of molecular hydrogen on platinum is produced without barriers and dissocia-tively (432 kJ mol 1 of dissociation energy) in different configurations that are able to reconstruct the surface. This makes the hydrogen adsorption state attractive for reduction reactions because of its low stabilization energy. 

Kustov L M and Kazansky V B (1991), Infrared spectroscopic study of the interaction of cations in zeolites with simple molecular probes. Part 1. Adsorption of molecular hydrogen on alkaline forms of zeolites as a test for localization sites , J Chem Soc, Faraday Trans, 87, 2675. 

Senchenya 1 N and Kazansky V B (1988), Nonempirical quantum-chemical study of the adsorption of molecular hydrogen and the mechanism of its heterolytic dissociation on aluminium oxide , Kinet Catal, 29, 1158. 

Serykh A1 and Kazansky V B (2004), Unusually strong adsorption of molecular hydrogen on Cu" sites in copper-modified ZSM-5 , Phys Chem Chem Phys, 6, 5250. 

Researchers have reported the influence of various chemical species on the performance of palladium-based membranes. Observed reductions in hydrogen flux through dense metal membranes are typically attributed to the blocking of the adsorption of molecular hydrogen, which is a necessary step in the atomic transport mechanism [13, 80,112,114,120-123],... 

The adsorption of hydrogen on metal electrodes such as platinum has been studied extensively in electrochemical systems over the last several decades. The mechanism for the hydrogen oxidation reaction on a Pt electrode in an acid electrolyte proceeds through two pathways, Tafel-Volmer and Heyrosky-Volmer, both of which involve the adsorption of molecular hydrogen followed by a... 

Since an elementary step represents a molecular event, its equation Jor reaction may not be written arbitrarily. Rather it must be written the way it takes place. Many errors are perpetrated for lack of adherence to this rule. Thus again, Example Ila in the table, the adsorption of molecular hydrogen at the surface of a solid catalyst to give two adsorbed hydrogen atoms, may not be written as ... 

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