AN IODINE TRIIODIDE REDUCTION ELECTROCATALYST FOR AQUEOUS AND ORGANICMEDIA/

In view of the use of organic electrolytes in solar energy conversion systems and the imminent need to minimize energy efficiency losses and performance limitations imposed on the system by iodine reduction on the counterelectrode, a catalyst was developed. The specific temperatu re regime and procedure described for the thermal decomposition of pla tinum-chloride (platinum-bromide or possibly other Pt compounds) from anhydrous isopropanol (or possibly other organic solvents) produces an electrode interface that is a selective catalyst for iodine/triiodide reduction in organic electrolytes matching the kinetics reported in a queous iodide/iodine systems. This technology produces catalytic elect rodes that are electrochemically/chemically stable in their operating environment, in addition to providing superior mechanical endurance or robustness and good adherence to substrates. The catalyst has been st ructurally characterized as nanosized platinum metal clusters. The ver y low platinum loadings (less than 3 mu g/cm(2)) render these electrod es optically transparent, and economy in the quantity of platinum used is an additional advantage. The technology can be applied to all sola r energy conversion systems utilizing the iodide/triiodide redox coupl e as mediator or any iodide/triiodide-mediated electrochemical device involving. e.g., electrochromism, charge generation (fuel cells), or s torage.