Reduction of Cu(II) to Cu(I) in solid CsCuCl3

The solid state reaction Cu + Cu2+ → 2Cu+ in CsCuCl3 was studied at 499 K using a cell in which the Cu(II) sample was put between two copper discs. Mass changes, thickness of the product layer and the total electrical resistance of the cell were measured as a function of time, both with and without (spontaneous) applied voltage. Applied voltage had an asymmetrical effect: it increased the rate at the anodic side, with no change at the cathodic one. The process was found to be under diffusive control, following a parabolic relationship with time. It was interpreted in terms of the movements of Cu(I) ions and electron holes.