Electrocatalysis of anodic and cathodic oxygen-transfer reactions

摘要

The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO(sub 3)(sup (minus))) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO(sub 3)(sup (minus)) to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO(sub 3)(sup (minus)) to produce an adsorbed product. An electrocatalytic link between reduction of IO(sub 3)(sup (minus)) and reduction of PtO is indicated. In addition, on oxide-free Pt electrodes, the reduction of IO(sub 3)(sup (minus)) is determined to be sensitive to surface treatment. The electrocatalytic oxidation of CN(sup (minus)) is presented as an example of anodic oxygen transfer in Part II. The voltametric response of CN(sup (minus)) is virtually nonexistent at PbO(sub 2) electrodes. The response is significantly improved by doping PbO(sub 2) with Cu. Cyanide is also oxidized effectively at CuO-film electrodes. Copper is concluded to serve as an adsorption site for CN(sup (minus)). It is proposed that an oxygen tunneling mechanism comparable to electron tunneling does not occur at the electrode-solution interface. The adsorption of CN(sup (minus)) is therefore considered to be a necessary prerequisite for oxygen transfer. 201 refs., 23 figs., 2 tabs.