Electrochemical Activation of Carbon-Halogen Bonds: Electrocatalysis at Palladium-Copper Nanoparticles

Palladized Cu nanoparticles (Pd/Cu NPs) supported on glassy carbon (GC) were synthetized by electrolytic deposition of Cu on GC, followed by galvanic displacement of Cu with Pd. The electrodes were characterized by XPS and EDX, which show that, although the composition of the NPs depends on the deposition time of Pd, Cu is always the main component, whereas Pd is preferentially limited to the uppermost layer of the nanoparticle surface. The reductive cleavage of a series of organic chlorides was investigated at Cu, Pd, Cu NPs and Pd/Cu NPs both in DMF and DMF/H2O (3/1 v/v). A strong dependence of the electrocatalytic properties of the electrodes on the mechanism of dissociative electron transfer (DET) was observed in pure DMF; moderate electrocatalysis was found for the reduction of all alkyl halides undergoing concerted DET, whereas no appreciable catalysis was observed for the reduction of aromatic chlorides, which undergo stepwise DET. However, addition of H2O remarkably enhances the catalytic activity of the metals. In DMF/H2O, all investigated compounds are catalytically reduced at Cu, Cu NPs and Pd/Cu NPs with good to excellent catalytic effects.