Strong electrostatic adsorption

The Extension of Strong Electrostatic Adsorption to Alumina and Carbon.185... 

Finally, the dispersion data in Figure 6.23 and Figure 6.25 indicate that it is possible to control the particle size of Pt. Strong electrostatic adsorption with drying at 100°C and reduction at 200°C can be used to prepare particles with 100% dispersion, that is, where each metal atom is accessible for catalytic reaction. Larger particles can be produced by calcining at higher temperatures. 

The whole idea of strong electrostatic adsorption (SEA), then, is to control the pH of the excess liquid so as to arrive at the optimal pH where metal complex-surface interaction is strongest. Calculations and experimental vah-dation such as seen in Figures 3.1b and 3.2 can be used to anticipate the initial pH that gives the optimal final pH. The pH buffering effect has been reviewed in more detail [15] and will be discussed further in the last section of this chapter. 

Strong Electrostatic Adsorption of Metals onto Catalyst Supports... 

To achieve strong electrostatic adsorption over a catalyst support, attention must be paid to achieving the optimal (equilibrium) value of pH. This is not so straightforward, due to the coupling of the protonation-deprotonation chemistry of the surface hydroxyl groups with the bulk solution pH (see Figure 13.2). 

FIGURE 13.8 Pt/silica catalyst synthesis by strong electrostatic adsorption (SEA) (a) electrostatic mechanism, (b) PTA uptake-pH survey to locate optimal pH over silica, (c) reduction of sample prepared at optimum conditions yields 1 nm metal particles. 

It can be generalized that the role of modifiers in the electron transfer process between the electrodes and redox proteins consists mainly in their capability to form a suitable electrode/electrolyte solution interface. At this interface only such surface configurations of the proteins are possible which prevent their strong electrostatic adsorption resulting in more extensive denaturation changes of the protein molecule [207,210,212]. 

Synthesis and characterization of highly loaded Pt/carbon xerogel catalysts prepared by the Strong Electrostatic Adsorption method... 

Fig. 1. (a) Principles of the Strong Electrostatic Adsorption (SEA) method depending on the PZC of the support and on the impregnation pH, the adsorption of ositively or negatively charged species is favoured (b) due to steric effects, the Pt uptake is limited and the Pt surface density vs. pH curve presents a maximum (results from [4]). 

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