Oxidation overpotential

C bond at low temperatures and to oxidize adsorbed CO at lower potentials, i.e., to reduce the oxidation overpotential. 

Direct electron transfer between CCP and an electrode was first reported (45) for the nonphysiological one-electron reduction and reoxidation of ferric CCP at fluorine-doped tin oxide. Overpotentials of around 0.5 V were required to drive this electrode reaction in either direction at measurable rates. A more successful approach to direct electroreduction of compound I, described by Armstrong and Lannon (46), employed edge-plane graphite electrodes in the presence of... 

Oxidation overpotential is said to occur if the potential of the metal is increased, relative to E M, as would be accomplished by attaching the positive terminal of a battery to the metal, thus raising the potential by removal of electrons. (This also induces metal ions to pass into solution.) A somewhat more descriptive statement is that for oxidation overpotential the metal is attached to an electron sink, such as a more noble half cell or the positive terminal of a battery, the negative terminal of which is attached to an inert electrode such as platinum,... 

With an oxidation overpotential, the removal of electrons from the electrode makes it more positive relative to the solution, an effect that the electrode attempts to counteract by increasing the rate of transfer of ions from metal to solution (i.e., ioxM is increased and iredM is decreased relative to their equilibrium value, i0 M), giving a net oxidation current density. 

Other recent studies focused on the understanding of the role of ad-atoms on the catalytic performance (in terms of both catalytic activity and glycerol oxidation overpotential) of Pt-based [11,65] and Pd-based [32,66] materials towards glycerol electro-oxidation in acidic and alkaline medium. 

Overpotentials may be positive or negative. The sign is determined by the nature of the process overpotentials for reduction are negative, since a more negative potential is more reducing. Conversely, overpotentials for oxidation are positive, since a more positive potential is more oxidizing. Overpotentials are not limited to reactions. They can be applied to electrode and electrolyte resistance, and to more complex processes, such as mass transfer limitations. Thus, overpotentials for cathodes are negative, whereas those for anodes are positive. In all cases, overpotentials express inefficiencies of the process. 

With the values of reversible and actual electrode potentials in L8-L11, the respective cathode and anode overpotentials are given in fines L12 and LI 3. Note that overpotential has units of Volts, since the effect of a reference electrode cancels in Eqs. 1 and 7. As mentioned above, overpotential is defined with respect to an increase in thermodynamic driving force. Thus, cathode (reduction) overpotentials are negative and anode (oxidation) overpotentials are positive. The cell overpotential will therefore be negative, according to Eq. 7. 

Platinum (Pt)-based catalysts are widely used as the anodic electrode material for hydrogen oxidation. The HOR on Pt catalysts has a lower oxidation overpotential and a higher kinetic rate. The apparent exchange current density of the HOR has been calculated to be =Q. Acm, which is extremely high... 

Potential loss in the bulk membrane (V), Equation 1.36 Ruthenium oxidation overpotential (V), Equation 5.231 Total cell overpotential (V), Equation 1.38 Heaviside step function... 

Redox films ean be produeed by electropolymerization of small redox molecules, whieh retain redox ehemistry in the polymerized state. The suggested structure of a polymerie version of poly (methylene blue) is shown in panel H of Table 9.1 [60]. In 1996, Zhou et al. demonstrated that methylene green could be electropolymerized on an electrode surface, resulting in a film with a half-wave potential in the vicinity of 0.21 V versus the standard hydrogen electrode (SHE) [100]. Furthermore, their work showed that this film eould mediate to NADH, reducing the required oxidation overpotential by 400 mV. Similar polymers have been demonstrated to mediate to NAD/NADH, sueh as poly(neutral red) [101]. 

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