Adsorption during atomization oxygen

Fig. 6.12. The kinetics of emission of O-atoms and adsorption of molecular oxygen during interaction of O2 with silver at 365 (/, 4), 320 (2) and 290 C.

Recently a novel experimental approach using Schottky diodes with ultra-thin metal films (see Fig. 11) makes direct measurement of reaction-induced hot electrons and holes possible. See for example Refs. 64 and 65. The chemical reaction creates hot charge carriers which travel ballistically from the metal film towards the Schottky interface and are detected as a chemicurrent in the diode. By now, such currents have been observed during adsorption of atomic hydrogen and deuterium on Ag, Cu and Fe surfaces as well as chemisorption of atomic and molecular oxygen, of NO and N02 molecules and of certain hydrocarbons on Ag. Similar results have been found with metal-insulator-metal (MIM) devices, which also show chemi-currents for many exothermic surface reactions.64-68... 

We shall assume that the surface of the catalyst contains chemisorbed atomic oxygen and that it is these chemisorbed oxygen atoms that act, when in the ion-radical state, as adsorption centers for CO molecules. In this case, during the adsorption of CO molecules, surface ion radicals C02-are formed as intermediate compounds, which, after being preliminarily neutralized, are desorbed in the form of C02 molecules. 

The DFT study of adsorption of silver dimer on rutile (110) surface within the cluster and periodic models shows that the interaction occurs both with chain oxygen atoms of the surface and with atoms located between the chains of 0(2c) atoms. Positive binding energy of Ag2 with rutile surface during adsorption between the oxygen chains was obtained only for the periodic model. The latter is concluded to be the preferable for theoretical study of Ag /Ti02 systems. 

It is important to control the surface area of manganese sulfide inclusions. During the rolling process for pipeline manufacture, for example, these inclusions get flattened to form platelets. This ino-eases the available surface area for hydrogen adsorption and therefore increases material susceptibility to HIC. One way to control this is the addition of calcium to ladle steel. Calcium reduces the oxygen and sulfur content of the steel. Calcium also results in the spheroidization of sulfide inclusions, thereby decreasing the available surface area for adsorption of atomic hydrogen. 

We used polycrystalline films of ZnO and Sn02 as adsorbents. The films were deposited from the water suspension of respective oxides on quartz substrates. These substrates contained initially sintered contacts made of platinum paste. The gap between contacts was of about lO" cm. All samples were initially heated in air during one hour at T 500 C. We used purified molecular oxygen an acceptor particle gas. H and Zn atoms as well as molecules of CO were used as donor particles. We monitored both the kinetics of the change of ohmic electric conductivity and the tangent of inclination angle of pre-relaxation VAC caused by adsorption of above gases and the dependence of stationary values of characteristics in question as functions of concentrations of active particles. 

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