Working potential

In the case of Cleanser Chemicals, Inc., the company formed a multifunctional team to assess commonalities across its existing Safety, Loss Prevention, Security, Medical, Industrial Hygiene and Environment functions. As a result of this assessment, many common requirements and potential work processes were identified, including ... 

Electrode Active Potential- Working Selectivity Recom- Tempe- Electrical Recom- Manufac-... 

As the cell is discharged, Zn2+ ions are produced at the anode while Cu2+ ions are used up at the cathode. To maintain electrical neutrality, SO4- ions must migrate through the porous membrane,dd which serves to keep the two solutions from mixing. The result of this migration is a potential difference across the membrane. This junction potential works in opposition to the cell voltage E and affects the value obtained. Junction potentials are usually small, and in some cases, corrections can be made to E if the transference numbers of the ions are known as a function of concentration.ee It is difficult to accurately make these corrections, and, if possible, cells with transference should be avoided when using cell measurements to obtain thermodynamic data. 

Figure 4.41. Effect of Ag/YSZ catalyst potential, work function and feed partial pressure of dichloroethane on the selectivity to ethylene oxide (a) and to acetaldehyde (b). T=270°C, P=500 kPa, 8.5% 02,7.8% C2H4.77 Reprinted with permission from Academic Press.

The Work Function of Catalyst Films Deposited on Solid Electrolytes Rationalization of the Potential-Work Function Equivalence... 

In section 5.4.3 we have discussed the physical meaning and range of validity of the potential-work function equivalence equations of solid state electrochemistry ... 

In view of the potential-work function equivalence of solid state electrochemistry (Eq. 4.30 or 5.18) and of the fact that for non-activated adsorption, AEd>Pt=0=A AHo,pt, where AHo.pt is the enthalpy of chemisorption of O on Pt, these equations can also be written as ... 

This isotherm is consistent with the modified electrochemical Langmuir isotherm, the Nemst equation and the potential-work function equivalence. For intermediate 0j and Pj values the isotherm of Eq. (6.58) is well approximated both by the Fowler-Guggenheim and by the Temkin isotherms. 

THE WORK FUNCTION OF CATALYST FILMS DEPOSITED ON SOLID ELECTROLYTES RATIONALIZATION OF THE POTENTIAL -WORK FUNCTION EQUIVALENCE... 

Figure 9.10. Ethylene epoxidation on Ag/p"-Al203 Transient effect of a negative applied current (Na supply to the catalyst) on the rates of ethylene oxide and C02 formation and on catalyst potential (work function) and Na coverage22 T=260°C, P=5 atm, p02=17,5 kPa, Pc2H4=49 kPa, 0.6 ppm C2H4CI2. Reprinted with permission from Academic Press.

Fig. 7. Photoelectric work function for Au, Pt and Ag electrodes emersed from 0.1 M HC104 at different potentials. Work function was measured by means of UPS (He 1). Arrows indicate work functions of clean polycrystalline surfaces. After [20].

The membrane potential and the concentration gradient can reinforce each other or they can be in opposition to each other. The total force tending to move a molecule or ion through a membrane is called the electrochemical potential. When the concentration gradient and the electrical potential work to oppose each other, the stronger effect wins. If someone forces you to get quantitative (this may be a physiologist rather than a biochemist), see the section on the Nernst equation at the end of the chapter. 

Table 4.1 Ionization potential, /, work function, (p, sputter yield, Y, and secondary ion yield of positive ions, R Y, of selected elements and their oxides.

Substance or Substance Class Detection Potential Working Electrode Material Reference Number... 

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