Charge accumulation in nanoheterogeneous iridium oxide films

Iridium oxide films with different values of crystallinity degree K are syn thesized. Properties of the films and their morphological features are exam ined. The charging of the films in a 1 M H2SO4 solution is studied voltamme trically. The most amorphous films (K = 0.08-0.26) acquire the largest over all charge q (in a fixed potential ran ge) relative to films with higher cr ystallinity degrees; however, the q vs. K dependence is not additive, and t he charge remains virtually invariant beginning with K greater than or equa l to 0.26. The contribution of slow charging processes, which is quite perc eptible in the amorphous films, is absent in samples with higher crystallin ity degrees, which have faster charge kinetics. The fast charging processes , which are not limited by diffusion, occur in boundary regions of IrO2 cry stallites (and/or the "oxide" part of a crystalline hydrated iridium. oxide ) and the amorphous phase. The transport of charge-compensating ions in the boundary regions occurs without considerable complications, as in the loos e network of amorphous phase IrO2 . xH(2)O. The assumption about the format ion of a "metallic" highly-conducting IrO2 cluster at K greater than or equ al to 0.26 is substantiated. The cluster rules out large resistances in the course of charge transport, which is a possible reason for the slow chargi ng of amorphous films with K < 0.26.