Electrochemical activation of carbon–halogen bonds: Electrocatalysis at silver/copper nanoparticles

• Spherical and polyhedral Cu NPs were loaded on GC via double step deposition.
• Ag/Cu NPs were obtained via galvanic displacement of Cu NPs with Ag salt.
• Ag in the form of very small NPs is confined on the Cu NPs surface.
• Cu NPs are as active as bulk Cu electrode toward R–X reduction.
• Ag/Cu NPs are even more active than bulk Ag and Cu toward R–X reduction.

Cu nanoparticles (NPs) of average dimension of 20–30 nm were deposited following a double step potential deposition on glassy carbon (GC). Cu NPs morphology, shape, dimension and distribution were investigated by scanning electron microscopy (SEM). According to SEM the electrochemical deposition of Cu produces two different type of NPs (spherical and polyhedral), which result randomly distributed all over the GC support. In a second step, Ag was deposited over Cu NPs by displacement deposition giving a Cu nanostructured electrode decorated with very small Ag NPs (hereafter Ag/Cu). The electrodes were fully characterized by X-ray photoemission spectroscopy and energy dispersive X-ray spectroscopy, which provided the surface and bulk chemical composition of the electrodes.The reductive cleavage of a series of organic chlorides, including chloroaromatics, benzyl chlorides, trichloroethylene and polychloromethanes, was investigated both at Cu and Ag/Cu NPs in DMF + 0.1 M (C2H5)4NBF4. Cu and Ag/Cu NPs electrodes have shown remarkable electrocatalytic reduction properties for the halides following concerted dissociative electron transfer. The peak potentials recorded at Cu and Ag/Cu NPs electrodes at v = 0.2 V s−1 are positively shifted by 0.3–0.5 V with respect to the reduction potentials measured at a non-catalytic electrode such as GC and in some cases the catalytic effect is even better than bulk Ag and Cu.

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