OHp = outer Helmholtz plane

Fig. 5-8. An interfadal double layer model (triple-layer model) SS = solid surface OHP = outer Helmholtz plane inner potential tt z excess charge <2h = distance from the solid surface to the closest approach of hydrated ions (Helmluritz layer thickness) C = electric capacity.

Pig. 5-27. Contact ion adsorption on metal electrodes in aqueous solution IHP = inner Helmholtz plane OHP = outer Helmholtz plane i,d = adsorbed ion ih = hy-dratedion oM = charge on the metal electrode o i = charge of adsorbed ions o i = charge of excess hydrated ions in solution. [From Bockris-Devanathan-MuUer, 1963.]... 

Fig. 7-2. Electron transfer of hydrated redox particles and of dehydrated adsorbed redox particles across an electrode interface (a) electron transfer of hydrated redox particles, (b) electron transfer of dehydrated and adsorbed redox particles on electrodes. (RED., OX,q) = hydrated redox particles (RED.d, OX.d) = dehydrated and adsorbed redox particles on electrode OHP = outer Helmholtz plane, IHP = inner Helmholtz plane.

Fig. 8-1. Potential energy barrier for tunneling transfer of electrons across an interface of metal electrode (a) cathodic electron transfer from an occupied level of metal electrode to a vacant level of l drated oxidant particles, (b) anodic electron transfer fiom an occupied level of hjrdrated reductant particles to a vacant level of metal electrode. M. = electrode surface OHP = outer Helmholtz plane cfuh = Fermi level of electnms in metal electrode. [From Gerischer, I960.]...

Fig. 9-7. Ionization of surface at oms followed by ion tnnsfer across an electrode interface in anodic dissolution of covalent semiconductor S = covalently bonded atom in semiconductor S. = surface atom of semiconductor s = surface radical = surfisce ion 825 = hydrated ion OHP = outer Helmholtz plane.

Figure 4.11. Triple-layer model (Grahame) IHP, inner Helmholtz plane OHP, outer Helmholtz plane (, water dipole +, positive end of the dipole).

What, therefore, is the potential difference to be used Is it MzfraP< ), the potential difference from the metal to the contact adsorption plane, or IHP (inner Helmholtz plane, see Fig. 6.88), or is it MzfOHP<[>, the potential difference from the metal to the OHP (outer Helmholtz plane, see Fig. 6.88), or MzfSpotential difference from the bulk of the metal to the bulk of the electrolytic solution In respect to P, does one consider it to multiply the whole potential difference across the interface or only a fraction of this potential difference Similarly, what concentrations of electron acceptors and donors must be fed into the basic equation Bulk values or the values at the OHP or the values at the contact-adsorbed species (Fig. 6.88) ... 

C is the potential difference between the oHp (outer Helmholtz plane) and the bulk of the solution (d potential). 

Apportioning the potential distributed across the oxide film, the inner Helmholtz layer and the outer Helmholtz layer, and assuming AV p to be constant with current based on dV/dq plots, b values of 120 mV were rationalized. A dK/d pH of -2.3RT/Fwasattributed topHdependenceof APo p, which results in R + = 1/2. (OHP = outer Helmholtz plane.)... 

Figure 14. Schematic representation of the electrode-solution interfacial region, (a) Helmholtz model (b) structured layer model (c) thermally disorganized layers and (d) resulting potential variations with distance of the electrode electrode potential Ojoi, solution potential OHP, outer Helmholtz plane (few A) Xq, extremity of the diffuse layer (few tens of A) x < xohP compact layer xqhp < x < x, diffuse layer.

Fig. 5.38. A. (a) An electrical double layer and (b) an electrical triple layer. B. Potential distribution at the interface. OHP = Outer Helmholtz Plane, IHP = Inner HP, <1> = Galvani potential.

OHP Outer Helmholtz plane. See Helmholtz Double Layer. 

FIGURE 1. A situation where the excess-charge density on the OHP is smaller in magnitude than the charge on the metal. — q > I ohpI- The remaining charge is distributed in the solution. The solvation sheaths of the ions and the water molecules on the electrode are not shown in the diagram. OHP, outer Helmholtz plane. 

FIGURE 17. Interfacial barrier at the n-type semiconductor-solution interface. The distribution of electronic states in ions in solutions is also given. OHP, outer Helmholtz plane. 

Fig. 2.1 Grahame s model of the electrochemical double layer. Anions and cations characterised by — or + signs, respectively. IHP inner Helmholtz plane and OHP outer Helmholtz plane. Reproduced from [19], with permission...

Figure 3. Schematic representation of an electrochemical double layer considered in Refs. 25, 26 S = solution Me = electrode IHP = inner Helmholtz plane OHP = outer Helmholtz plane Fh = potential drop in the Helmholtz layer Ko.ch = potential drop in the diffuse layer and x-distance from an electrode into solution.

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