Surface oxygen-terminated

Fig. 26. STM images of the oxygen pre-covered platinum(l 1 1) surface during reaction with hydrogen. Images were recorded at a temperature of T = 111 K with a time interval of 625 K. The white ring in the upper right corner is associated with a reaction front of OH intermediates from the autocatalytic reaction. The outside is characterized by an oxygen-terminated surface, whereas water molecules from the reaction are identified inside the ring. Adapted with permission from Reference (757).

Diamond surfaces after anodic oxidation treatment involve oxygen-containing surface functional groups. The electron-transfer kinetics for ions and polar molecules are expected to be quite different. Fe(CN)l /4 was highly sensitive to the surface termination of diamond. For an anionic reactant, there was an inhibition of the electron transfer for the oxygen-terminated diamond electrodes compared with the hydrogen-terminated diamond electrodes, and there was also an acceleration of the electron transfer for oxygen-terminated diamond for some cationic reactants such as Ru(NH3) +/3+ and Fe2+/3+. These results can be explained by electrostatic effects, which interact between the ionic... 

Zincite is usually colored red or orange by manganese impurities. Photographs of zincite are shown in Fig. 1.2. Zinc oxide crystals exhibit several typical surface orientations. The most important surfaces are the (0001) and (0001) (basal plane), (1010) and (1120) (prism planes) and (1121) (pyramidal plane) crystal faces. In principle, the (0001) planes are terminated by Zn atoms only, while the (0001) surfaces are terminated by oxygen atoms only. However, this simple picture does not hold in reality (see description of the surface structure in Sect. 4.2.1 of this book). Nevertheless, the etching behavior is noticeably different for these two surfaces [17] (see also Chap. 8). 

The wurtzite lattice of ZnO and its low-index surfaces are shown in Fig. 4.5. The basic low index surface terminations are (0001), (0001), (1010), and (1120). The (0001) and (0001) represent the zinc and oxygen-terminated surfaces of the polar 0001 direction, which corresponds to the 111 direction of the cubic zincblende lattice. In contrast to the polar (100) and (100) surfaces of the zincblende lattice, the surfaces with threefold symmetry (111)... 

The work functions and ionization potentials of sputter-deposited ZnO and ZnO Al films are shown in Fig. 4.13. The different Fermi level positions of ZnO and ZnO Al for deposition at room temperature in pure Ar are also observed in the work function. The undoped films prepared under these conditions have a work function of 4.1eV, while the Al-doped films show values of 3.2eV. The difference is almost of the same magnitude as for the Fermi level position and, therefore, explained by the different doping level. Also the ionization potentials are almost the same under these preparation conditions. The work function of the undoped material is close to the value reported by Moormann et al. for the vacuum-cleaved Zn-terminated (0001) surface [20], The same authors report a work function of 4.95 eV for the oxygen terminated ZnO(OOOl) surface, which is in good agreement with the values obtained for films deposited with >5% oxygen in the sputter gas. Since the Fermi level position of the undoped ZnO films does not depend on the oxygen content in the sputter gas (Fig. 4.12), the different work functions correspond to different ionization potentials. 

Fig. 8.14. SEM micrographs of etched ZnO single crystals. The crystals were etched either in hydrochloric acid (top) or in sodium hydroxide solution (bottom). The graph shows the zinc terminated (001) (left) and the oxygen terminated (001) (right) surface after the respective etching step. The angles 7 spanned by the two opposite edges and <5 between the (101) faces of the etch crater are about 130° and 123°, respectively...

In the cited work (Ivandini et al. 2006), the authors outlined that the oxygen-terminated BDD performed worst than the hydrogen-terminated one because the carboxyl functional groups of the oxalic acid molecule may be repulsed by the negative O-terminated electrode surface. 

The polyhedral (MO ) building blocks of virtually all polyoxoanions are linked in such a way as to result in each polyhedron having either one or two (mutually cis) unshared vertices. The metal atoms are displaced from the centers of their coordination polyhedra toward these unshared vertices. These displacements correspond to the formation of short metal oxygen terminal bonds resulting from oxygen Pjt donation into the metal s vacant d-orbitals. Such terminal oxygens, which are very weakly basic, form part of the external surfaces of the polyoxoanions and effectively prevent fruther polymerization. Very rarely (about three examples... 

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