Palladized silver as new cathode material: Evidence of a one-electron scission for primary alkyl iodides

Abstract

Silver electrodes modified by ‘‘palladization” thanks to an immersion in acidic solutions of Pd2+ salts, exhibit exceptional catalytic capabilities especially in the cleavage of primary alkyl halides used as standard systems in order to evaluate the catalytic activity. Such chemically modified surfaces characterized by the formation of an Ag/Pd-based alloy showed large potential shifts compared to the use of glassy carbon or even smooth silver cathodes. Specifically, these palladium-doped silver surfaces were successfully used for cleaving carbon–iodine bonds. Thus, preliminary results have revealed that palladized silver electrodes behave quite differently from smooth silver and showed exceptional catalytic capabilities. Cathodic reductions were achieved in dimethylformamide, acetonitrile, and propylene carbonate. While smooth silver cathodes generally entailed two-electron cleavage reactions (evidence of two clearly separated steps in propylene carbonate), palladized silver interfaces always yield catalytic cleavages of carbon–iodine bonds according to single one-electron processes with the transient formation of a free alkyl radical leading to homo-coupling processes.