An Iodine/Triiodide Reduction Electrocatalyst for Aqueous and Organic Media

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 temperature regime and procedure described for the thermal decomposition of platinum‐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 aqueous iodide/iodine systems. This technology produces catalytic electrodes that are electrochemically/chemically stable in their operating environment, in addition to providing superior mechanical endurance or robustness ana good adherence to substrates. The catalyst has been structurally characterized as nanosized platinum metal clusters. The very low platinum loadings (less than 3 μg/cm2) render these electrodes optically transparent, and economy in the quantity of platinum used is an additional advantage. The technology can be applied to all solar energy conversion systems utilizing the iodide/triiodide redox couple as mediator or any iodide/triiodide‐mediated electrochemical device involving, e.g., electrochromism, charge generation (fuel cells), or storage.