Current density reduction

Figure 8. Dependence of the BOD-catalyzed oxygen reduction current density on the difference in formal potentials between the O2/H2O couple and a range of cyano-metal complexes (M) for three values of solution pH. Arrows indicate reported values of the BOD formal potential F (Enz) relative to that of O2/H2O. Reproduced with permission from ref 159. Copyright 2003 Elsevier Science B.V.

Eor the reduction reaction of reaction (6.6), the reduction current density is... 

With an n-type Si electrode, the reduction current density increases exponentially with decreasing potential, the apparent Tafel slope was found equal to 140-160 mV/decade. This is much higher than the 60mV/decade required for the processes that are limited by the supply of electrons from the semiconductor whose space charge is under the accumulation regime. In other words, the HER at the Si surface is a slow electron transfer, that is, a relatively large overpotential is required to... 

In Section 2 we showed that the properties of amorphous carbon vary over a wide range. Graphite-like thin films are similar to other carbonaceous materials (glassy carbon, and the like) in their electrode behavior. Redox reactions proceed in a quasi-irreversible regime on these films. In particular, the cathodic reduction of nitrate previously studied on crystalline diamond electrodes (see Section 6.4.2) was performed with amorphous carbon films prepared by UHV laser deposition and comprising both sp2- and sp3-carbon [152], Reduction current density as high as 2 mA cur 2 was reached in neutral or alkaline solutions. The use of such electrodes in microgravimetry is discussed [153]. 

Fig. 3.4 Diagram illustrating dynamic equilibrium for the metal reaction M = Mm+ + me, where the oxidation current density, iox M, is equal to the reduction current density, ired M.

A corresponding model for the reduction reaction, Mm+ + me —> M, is expressed as a reduction current density in the form ... 

Since Eq 3.14 and 3.19 have been derived on the basis of equilibrium, the oxidation and reduction current densities must be equal and equal to the exchange current density ... 

In the derivations of Eq 3.14 and 3.19 for the metal oxidation current density, iox M, and the metal-ion reduction current density, ired M, it was not necessary to restrict the half-cell potential to its equilibrium value. Deviation from E M will occur if the potential of either the metal or the solution is changed, resulting in an overpotential defined in general by Eq 3.1. More specifically, small deviations are associated with charge-transfer polarization, and the overpotential is designated as ... 

It should be noted that Eq 3.41 and 3.42 have the relatively simple form of an exponential term involving the overpotential, r CT, multiplying the exchange current density to give the current densities of the oxidation and reduction components of the polarized half-cell reaction. When an overpotential exists, the oxidation and reduction current densities are no longer equal When r CT > 0, then iox M > ired M, and when r CT < 0, then ired M > i0X M-... 

The total oxidation and reduction current densities will be equal at the point at which the anodic line for the metal dissolution reaction intersects the cathodic line for hydrogen evolution. The potential at which these lines intersect is the corrosion potential. The rate of the anodic reaction at the corrosion potential is the corrosion rate (corrosion current density). The corrosion potential always takes a value between the reversible potentials for the two partial reactions. 

PPy/Au/ITO Oxygen reduction CV Increase in reduction current density [33]... 

Impurity Reduction Current density Days on line (/) i X t... 

The reduction current density i of Ru(NH3)6 across SAMs of n-alkanethiols with 8 < nc < 18 from aqueous 0.5 M KCl was thoroughly investigated by Majda and coworkers [85,... 

Figure 6.43 Rotating ring-disk experiment of passive film breakdown on Fe after injection of chloride ions. Parameters observed to vary as a function of time the current density of the disk the reduction current density of Fe " on the ring and the current density of formation of Fe on the disk. Electrolyte is borate solution of pH 7.3. Concentration of NaCl added at time t = 0 is O.Olmol 1 Dashed line shows the time to reach a uniform NaCl concentration [41].

Potentiodynamic (5 mV s positive sweep) O2 reduction current densities (/d) on the thin film RRDE with Pt/Vulcan catalyst (14 pgpt cm ) at 60 °C In 0.5 M H2SO4 saturated with 1 bar O2. (b) simultaneously recorded ring currents (/r) at 400 and... 

Figure 10 Oxygen reduction current density on stainless steel erqxrsed to natural seawater and continuously polarized at fixed cathodic potentials. The envelopes of cmves 1 and 2 correspond to the set of data on clean and already fottled stainless steel sttrfaces, respectively [83],...

---