Dissolution of platinum in methoxy propionitrile containing LiI/I2

The stability of vapour deposited Pt and Pd as electrocatalysts on fluorine doped, tin oxide coated glass for the use as counter electrodes in dye senzitized electrochemical solar cells has been investigated. The electrocatalytically active layers did not seem to be chemically stable in an electrolyte consisting of LiI and I₂ dissolved in methoxy propionitrile. Thermodynamical calculations suggest the dissolution of Pt and Pd from the electrode surface to be caused by the formation of PtI₄ and PdI₆. Formation of complex species as PtI²⁻₄ and PdI²⁻₄ is less thermodynamically favoured, but PtI²⁻₄ may also be present in the solution.