Water oxide structure

Red lead is insoluble in water. Like lead(II) oxide it can readily be reduced to lead. The structure of the solid, as the systematic name suggests, consists of two interpenetrating oxide structures, in which each Pb atom is surrounded octahedrally by six oxygen atoms, and each Pb" by three (pyramidal) oxygen atoms, the oxygen atoms being shared between these two units of structure. With dilute nitric acid the lead(ll) part dissolves, and the lead(IV) part precipitates as lead(IV) oxide ... 

Because of their greater thickness, CAA oxides serve to protect the metal surface from corrosion better than thinner oxides but the important factor for bond durability is the stability of the outer oxide structure when water diffuses to the oxide-polymer interphase. Accordingly, it would be expected that the performance of CAA treated adherends would be similar, although no better, than that of PAA, or BSAA. The wedge test data shown in Fig. 20 and other work [29,77,97,98] support this and demonstrate that when these processes are done correctly the wedge test crack will be forced to propagate entirely within the adhesive. Similar arguments are likely with BSAA adherends, also. 

Huang YS, Chen YE (1988) Electronic-structure study of RuS2. Phys Rev B 38 7997-8002 Salvador P, Alonso-Vante N, Tributsch H (1998) Photoelectrocatalytic study of water oxidation at n-RuS2 electrodes. J Electrochem Soc 145 216-225... 

McEvoy, J.P. and Brudvig, G.W. (2004). Structure-based mechanisms of photosynthetic water oxidation. Phys. Chem. Chem. Phys., 6, 4754 1763... 

In contrast the oxo-ruthenium complex c ,c -[ (bpy)2Runl(0H2) 2(//-0)]4+ and some of its derivatives are known to be active catalysts for the chemical or electrochemical oxidation of water to dioxygen.464-472 Many studies have been reported473 181 on the redox and structural chemistry of this complex for understanding the mechanism of water oxidation. Based on the results of pH-dependent electrochemical measurements, the basic structural unit is retained in the successive oxidation states from Rum-0 Ru111 to Ruv O Ruv.466... 

In the third step, the chemical structure is used to determine if the substance is compatible with materials which are common to the process unit, such as air, water, oxidizers and combustibles, acids, alkalies, catalysts, trace metals, and process utilities (see Section 2.2.4). Even if the substance is considered to be a non-explosion hazard (both nonenergetic and compatible with the... 

The quadrupole splitting of the heat treated FePc/XC-72 electrode measured ex situ, prior to the electrochemical experiments, was larger than that found in situ. Smaller values for A have been reported for certain ferric hydroxide gels and for small particles of FeOOH (Table II), and thus the effect associated with the immersion of the specimen in the electrolyte is most probably related to the incorporation of water into the oxide structure. For this reason, the material observed in situ at this potential will be referred to hereafter as FeOOH(hydrated), without implying any specific stoichiometry. 

Figure 38 Structural models of the manganese complex which constitutes the active site responsible for the water oxidation in WOC...

SoUd ice forms a crystal of diamond structure, in which one water molecule is hydrogen-bonded with four adjacent water molecules. Most (85%) of the hydrogen bonds remain even after solid ice melts into liquid water. The structure of electron energy bands of liquid water (hydrogen oxide) is basically similar to that of metal oxides, 6dthough the band edges are indefinite due to its amorphous structure. 

I have presented an overview of the current state-of-the-art in studies of the Mn complex in photosystem II. There are many unresolved questions and a clear picture of the structure and function of Mn in photosynthetic water oxidation is still not available. One useful approach to help determine the structure of the Mn complex in photosystem II involves the synthesis and characterization of Mn model complexes for comparison with the properties of the Mn complex in photosystem II. Recently, several tetrameric high-valent Mn-oxo complexes have been reported (see the chapter in this volume by G. Christou). Further characterization of existing and new high-valent tetrameric Mn-oxo model complexes, especially EPR and EXAFS measurements, will no doubt help clarify the present uncertain picture of the structure of the Mn complex in photosystem II. 

Two proposals for the water oxidation cycle Involving Mn/0 assemblies established in synthetic complexes have been published to date. These have attempted to describe the structural rearrangements of the Mn core and concomitant substrate binding... 

In the wetted condition, hydrothermal transformations of the waste form may occur at the temperature of service. Changes may occur either by dissolution and re-precipitation or by assimilation of water into the internal structures of the oxide matrices. The thermochemical essentials for hydrothermal recrystallisation have already been referred to previously in this paper. We also need to develop an adequate knowledge of the water-catalysed structural transformations. 

In this type of cell both electrodes are immersed in the same constant pH solution. An illustrative cell is [27,28] n-SrTiOs photoanode 9.5-10 M NaOH electrolyte Pt cathode. The underlying principle of this cell is production of an internal electric field at the semiconductor-electrolyte interface sufficient to efficiently separate the photogenerated electron-hole pairs. Subsequently holes and electrons are readily available for water oxidation and reduction, respectively, at the anode and cathode. The anode and cathode are commonly physically separated [31-34], but can be combined into a monolithic structure called a photochemical diode [35]. 

Thus, a new layer of oxide is generated as schematically shown in Fig. 10. Water molecules are present in the oxide structure incorporated during the oxidation process. This water combines with... 

Nevertheless, we recall that, in alkaline solutions, the silanol groups are partly dissociated into —Si—0 anionic sites owing to their acido-basic character. As a result, this oxide structure is loose and is permeable to water molecules and chemical reactants, so that the reaction can proceed by diffusion through the layer and lead to a uniform protecting layer. The acido-basic character is well demonstrated by the transformation operated by dipping the oxidized sample in an acidic HCl solution. The polarization resistance, which was equal to a few 10 f2 cm, suddenly is... 

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