Mixed Potential, mp

the total current density, /total is composed of two components. It is a result of the addition of current densities of the two partial processes. 

When a catalytic surface S is introduced into an aqueous solution containing Mz+ ions and a reducing agent, the partial reaction of reduction, Eq. (43), and the partial reaction of oxidation, Eq. (44), occur simultaneously. Each of these partial reactions strives to establish its own equilibrium, Eeq. The result of these processes is a steady state with the compromised potential called the steady-state mixed potential, Em-p. The result of this mixed potential is that the potential of the redox couple Red/Ox, Eq. (44), is raised anodically from the reversible value eq.Red (Fig- 22) and the potential of the metal electrode M/Mz+, Eq. (43), is depressed cathodically 

the four basic characteristics of the steady-state mixed potential are as follows  

Both redox systems are shifted from their own characteristic equilibrium potentials by the amount i] (overpotential) 

A net electrochemical reaction occurs in each redox system since both reactions, Eqs (43 and 44), are shifted from their equilibrium by the introduction of the mixed potential. 

---

Steady-state electroless metal deposition at mixed potential mp is preceded by a non-steady-state period, called the induction period. 

Induction Period. The induction period is defined as the time necessary to reach the mixed potential mp at which the steady-state metal deposition occurs. It is determined in a simple experiment in which a piece of metal is immersed in a solution for electroless deposition of a metal and the potential of the metal recorded from the time of immersion (or the time of addition of the reducing agent), that is, time zero, until the steady-state mixed potential is established. A typical recorded curve for the electroless deposition of copper on copper substrate is shown in Figure 8.11 (31). 

Electroless Deposition of Copper. The basic ideas of the mixed-potential theory were tested by Paunovic (10) for the case of electroless copper deposition from a cupric sulfate solution containing ethylenediaminetetraacetic acid (EDTA) as a complexing agent and formaldehyde (HCHO) as the reducing agent (Red). The test involved the comparison between direct experimental values for mp and the rate of deposition with those derived theoretically from the current-potential curves for partial reactions on the basis of the mixed-potential theory. 

Elemental fluorine is produced commercially by the electrolysis of KF-2HF (mp 72 °C) using carbon anodes and steel cathodes. The voltage of the cells is 8-12 V (standard electrode potential for F2 = 2.85 V) and current is as high as 15kA, depending on cell size. The cathode and anode are separated by skirts to prevent mixing of F2 with H2 formed at the cathode. The western world production of fluorine is ca. 2-3 x 10 ta , of which about 55% is used for production of UFe and 40% is for SFe. Other uses include production of CF4, NF3, and fluorinated graphite for batteries. 

The authors have subsequendy surmised that MPS is resistant to the anabolic qualities of insuhn driven by mixed meals in the elderly. They clearly demonstrated that AA supplementation alone can overcome at least some of the age-related redueed stimidation (e.g., movement) or diminished sensitivity to normal anabohc faetors, suggesting a potential justification for long-term use of AA supplementation as a nutritional strategy for sarcopenia. 

---