Hydroxide ions, reaction diameter

JLm diameter spheres, called lepispheres, which are composed of bladed crystals 30-50 nm thick. Kastner et al. (1977) reported that the formation of opal-CT results from dissolution followed by reprecipitation reactions that require a source of magnesium, alkalinity, and hydroxide ion. The presence of aluminosilicate phases commonly retards the formation of opal-CT (Hinman, 1998). 

In the above sections, we have presented the electrode kinetics of electron-transfer reaction and reactant transport on planar electrode. However, for practical application, the electrode is normally the porous electrode matrix layer rather thtin a planner electrode siuface because of the inherent advantage of large interfacial area per unit volume. For example, the fuel cell catalyst layers are composed of conductive carbon particles on which the catalyst particles with several nanometers of diameter are attached. On the catalyst particles, some proton or hydroxide ion-conductive ionomer are attached to form a solid electrolyte, which is uniformly distributed within the whole matrix layer. Due to the electrode layer being immersed into the electrolyte solution, this kind of electrode layer is called the flooded electrode layer . 

The reaction diameter for the reaction between hydrogen ions and hydroxide ions in aqueous solution is larger than the sum of the radii of these ions. The explanation for this fact is that water molecules can exchange hydrogen and hydroxide ions as described in Chapter 10. 

Li et al. developed a solid-state reaction process to synthesize perov-skite-type LaCoOs NCs with grain diameters of 15 0 run (Li et al., 2002). In the first step of the preparation, 5 run composite hydroxide NPs were s)mthesized by grinding metal nitrates liquid paste and mixing with KOH. Then the composite powders were calcined at 800 °C, yielding a single-phase oxide. Tien-Thao et al. prepared LaCo Cui J.O3 x < 0.3) by mechano-synthesis (Tien-Thao et al., 2008). The sample has various distinct Co " " ions in the perovskite lattice, which are more reducible. The reduced catalyst surface comprising cobalt and copper atoms is very selective for the hydrogenation of CO. 

The electrodeposition process can also be combined with an AAO template for the fabrication of a metal-embedded hollow nanotube structure, that is, Ni-embedded silica nanotubes, as demonstrated by Xu et al. [79]. The fabrication starts with the electrodeposition of multiple segments of Ag/Ni/Ag (3 pm/3 pm/ 3 pm) nanowires with a diameter of 300 nm on nanoporous AAO templates (Figure 13.7d). Subsequently, a hydrolysis reaction of tetraethyl orthosiUcate was performed for 2-5 h to coat a 70 nm thick silica layer. Then, Ag was selectively etched in a mixture (4 1 1) of methanol, hydrogen peroxide, and ammonia hydroxide to produce a hollow structure. Finally, Ag nanoparticles were functionalized on the surface by the reduction of Ag ions at 70 °C for 7 h in a composite solution of PVP (2.5xlO M in ethanol), silver nitrate (0.06 M), and ammonia hydroxide (0.12 M). The synthesized silica nanotubes exhibited a Ni-embedded hollow structure with Ag nanoparticles functionalized on the surface... 

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