Photochemlstry of Colloidal Semiconducting Iron Oxlde Polymorphs

working in the potential region where the film is not active toward the substrate employed. When the electrocatalyst employed (first coating) is very efficient, is can be. evaluated by using eq 7 ( i K is large and the third term can be neglected). Then quantities iA and iL are obtained from the limiting currents of the current-potential curves recorded with singleand double-coated electrodes (Figure 4). In the case where the electrocatalyst is not able to generate a diffusioncontrolled current (Levich current), the system should be analyzed in terms of Koutecky-Levich plots (Figure 5), where the difference of the intercepts of the parallel plots is a direct measure in I/is. The high diffusion current found for iron ions in the [Ru(bpy)zCl(PVP)]C1 fim is of interest. We believe that the uncoordinated protonated pyridine groups at the polymer backbone play an important role for the polymer to achieve this property. However, we can not exclude contributions from porosity.