EFFECT OF ELECTRODE MATERIALS ON KINETICS OF ELECTRON EXCHANGE REACTIONS

The electrode reaction Fe(CN)63-/Fe(CN) 64- is studied at sodium tungsten bronzes of compositions Na0.50WO3, Na0.70WO3, and Na 0.90WO3. The average standard exchange current densities of the order 101 A·cm mole-1 appear to be slightly dependent on the composition of bronzes. Transfer coefficient is found to be 0.5. On the basis of these results and those available in the literature for several redox reactions at various metals, a theory of heterogeneous electron exchange reactions is discussed. The influence of electrode material on the rate of electrode reaction is shown to depend on the density of states of electrons at the Fermi level of metals. The exchange integral, the other parameter where the influence of material should be contained, appears only slightly dependent either on a particular electrode reaction or on electrode material. Standard exchange current densities for some other redox reactions at platinum are predicted.