2.1 Materials: Cuprous oxide (Cu2O, Merck), a carbon gas diffusion layer (Fuel Cell Systems), and tin (IV) chloride pentahydrate (Merck) were used as precursors for the Sn and Cl deposition on the Cu2O-coated gas diffusion electrode. Potassium hydroxide (KOH, Merck) was used to prepare the electrolytes. Deionized water was used to prepare all solutions and to rinse the samples and glassware.