Smooth Polycrystalline Platinum Electrodes

Figure 2. Diagram of electrode in adsorption position and "squeezed" position for adsorbate measurement (1) smooth, polycrystalline platinum electrode (2) polished glass scintillator detector (3) Macor ceramic disk, which forms cell bottom ( )) resin (5) electrode shaft.

Fig. 32 Potential oscillations during formic acid oxidation at a smooth polycrystalline platinum electrode (a) 5 M HCOOH/0.5 M H2SO4, applied current density of 1.5 mA cm-2 (b) 1 M HCOOH and 0.5 M H2SO4, 0.25 mA cm [127].

Methanol Oxidation at a Smooth Polished Polycrystalline Platinum Electrode d 3.3—The Electrochemical Reduction of CO[sub(2)]... 

Methanol oxidation at a smooth polished polycrystalline platinum electrode... 

Adsorption of aniline on minerals, such as kaolinite, montmorillonite and vermiculite as well as on a-alumina and iron powders, has been studied in order to better understand the interaction of the adsorbate with natural adsorbents154-157. However, the results, similarly to those obtained on a smooth polycrystalline platinum electrode158, are not useful for the removal of aniline from waste water. The commonly used activated charcoal is also deficient owing to slow kinetics of the removal of dissolved pollutants. In this situation, activated carbon fibers, woven as a C-cloth, seem to be the ideal adsorbents for removal of aniline from waste streams. The reports of Niu and Conway159,160 explained the adsorptive and electrosorptive behavior of aniline on C-cloth electrodes and suggested a methodology for clean-up of industrial waste waters. 

When the fact of hydrogen adsorption on platinum metals was well documented, a search for self-consistent models started, aimed to description of surface hydrogen coverage dependence on electrode potential and temperature. Breiter was the first who studied the temperature dependence of hydrogen adsorption on smooth platinum, rhodium and iridium. He demonstrated a possibility to present experimental dependences typical for polycrystalline platinum by combination of two Fmmkin isotherms (see below in Section IV. 5). 

HOR studies on smooth noble metal surfaces in acidic media show that platinum is the most active. The reaction mechanism on bulk polycrystalline platimun electrode is usually assumed to proceed through a Tafel-Volmer mechanism via reactions (4) and (5), the dissociative adsorption of hydrogen being the rate-determining step (r.d.s.) [51]. In alkaline electrolytes, HOR on polycrystalline Pt follows a Tafel-Volmer sequence and the r.d.s. is the dissociative hydrogen adsorption given by reactions (4) and (6) [52]. 

---