Single oxides, surface and passive layers

O Grady et al. [227] studied the reduction and evolution of oxygen on RuO on titanium and reported that the cathodic reaction involves the formation of peroxide in solution. From y 1/2 vs. xi 1/2 plots obtained using rotating disk electrodes, the authors concluded that the reaction 02/H202 was in equilibrium at the surface [227], Miles et al. [428] also studied the oxygen electrode reactions on several metal oxides (Ir, Ru, Pd, and Rd) 

Danzfuss and Stimming [60] reported that oxygen reduction proceeds at 

The cathodic reduction of oxygen on catalytically active substrates is very inhibited by deposited hydrated oxide layers. Such is the case of Fe00H-xH20 (sandwich oxide electrode) on gold at pH 7.2 [94] and Ni(OH)2 deposited on platinum [447]. This inhibition is probably related to the electronic properties of the surface layer, since simple outer sphere couples are highly inhibited also (Sect. 5.3). 

Passive layers on copper and its alloys, which have technological relevance in corrosion, have been investigated in studies of oxygen reduction. Balakrishnan and Venkatesan [448] reported a two-step reduction of oxygen via peroxide on copper(I) surface oxides in neutral solutions. 

Although the thermodynamic potential for the oxygen electrode reaction [i.e. 1.229 V (RHE)] is lower than that of the chlorine electrode, in practice the kinetics of the chlorine electrode reactions are substantially faster than 

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