Oxygen adsorption and dissociation

A number of dissimilar surface compositions and structures develop at the NiAl ordered bulk alloy by preparation dependent effects. Completely different chemical behavior against oxygen adsorption and dissociation has been found for two CujAu surfaces, the (100) and (110) plane, consisting of the same surface composition. The (100) surface with Cu atoms surrounded by Au atoms turns up non-reactive alike Au. On the other hand, the (110) surface with Cu chains in the first layer acts similar to a Cu(l 10) surface. Intermixing or phase separation can be manipulated at CujAu too. Upon vanadium deposition on the bare alloy surface, strong intermixing and alloy formation towards a V3AU... 

Vines F, Sousa C, lUas F, Liu P, Rodriguez JA (2007) A systematic density functional study of molecular oxygen adsorption and dissociation on the (001) surface of group IV, V and VI transition metal carbides. J Phys Chem C 111 16982-16989... 

The TPO spectrum shows that the maximum of the N2 peak appears at lower temperature than the maximum of the N2O peak. This indicates that the production of N2O is dependent on the formation of NO(a) from NH(a) species or on the availability of free sites for oxygen adsorption and dissociation. 

The oxygen reduction reaction at the cathode (Eq. 4) can be broken down into several steps gas-phase diffusion, oxygen adsorption and dissociation at the cathode surface, surface or bulk diffusion of oxygen atoms, and incorporation into the electrolyte [4,5]. Any of these steps can limit the rate of cathodic reaction. The reaction site distributes three dimensionally aroimd the triple-phase boimdary (TPB) of electrode, electrolyte, and gas phase, as illustrated in Figme 2. In practical applications, LSM is often used as a composite with YSZ particles to increase the electrochemical reaction site. As YSZ can make a separate ionic path, the reaction site is made three dimensionally inside the electrode layer [6]. 

Hyman MP, Medhn JW. 2005. Theoretical study of the adsorption and dissociation of oxygen on Pt(lll) in the presence of homogeneous electric fields. J Phys Chem B 109 ... 

Figure 3.8 STM images of the same area on Ti02(l 1 0) at 357 K (V, = 1.5 V, /, = 0.1 nA) as a function of time (At = 60s) (a) clean Ti02(l 1 0) with bridging oxygen (BBO) vacancies (b) Ti02 (1 1 0) with a geminate hydroxyl pair formed by adsorption and dissociation of a water molecule. Hv marks the...

Another remarkable issue concerns the adsorption and dissociation of molecular oxygen on oxide surfaces. When such surfaces are metal terminated in UHV, the dissociative adsorption of oxygen may lead to oxygen terminations, very different from bulk terminations. This is exemplified for the case of CrjOsCOOOl). 

Epoxidation of butadiene occurs by addition of dissociatively-adsorbed oxygen to one of the localized C=C bonds to form epoxybutene. The addition of oxygen across the terminal carbon atoms does not occur to any measurable extent. The direct participation of molecular oxygen can be ruled out based both on selectivity arguments as well as the kinetic model for the reaction. The kinetics imply a dual site mechanism. One site, which is unpromoted, serves as the site for butadiene adsorption, while the second site, which is promoted, functions as the site for dissociative oxygen adsorption and epoxybutene formation. 

Fig. 8. One-dimensional potential energy diagram for the adsorption and dissociation of oxygen on an Ag catalyst after Dean and Bowker, 1989).

Evidence for the activation of the ammonia adsorption and dissociation promoted by oxygen on platinum is provided by PEP pulse experiments. The... 

A pre-oxidised catalyst deactivates much faster than reduced platinum sponge. Ammonia adsorption and dissociation are accelerated by the presence of oxygen. Thus, the NHx species cover much faster the platinum surface. The concentration profiles for nitrogen and nitrous oxide do not change, which indicates that the reaction mechanism is not changed for the pre-oxidised catalyst. 

A very important issue is the adsorption and dissociation of O2 on the Au/oxide systems since this seems to be a necessary step in total and partial oxidation reactions. " Can isolated Au nanoparticles dissociate O2 Is the Au/oxide interface necessary for the cleavage of 0-0 bonds Calculations based on density functional theory have been carried out for a series of unsupported Au nanoparticles as well as for extended systems containing low-coordinated sites. Strong adsorption of molecular oxygen on Au nanoparticles is a necessary but not sufficient condition for O2 dissociation. For reasonably large Au cubo-octahedral nanoparticles, there is a common pathway for O2 dissociation on nanoparticles which involves a particular configuration of adsorption sites and a critical particle size. If these conditions are not satisfied, the... 

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