Influence of the support material and the resulting particle distribution on the deposition of Ag nanoparticles for the electrocatalytic activity of benzyl bromide reduction

Abstract

Silver nanoparticles (NPs) were deposited on nickel, titanium and gold substrates using a potentiostatic double-pulse method. The influence of the support material on both the morphology and the electrocatalytic activity of Ag NPs for the reduction reaction of benzyl bromide was investigated and compared with previous research regarding silver NPs on glassy carbon. Scanning electron microscopy (SEM) data indicated that spherical monodispersed NPs were obtained on Ni, Au and GC substrate with an average particle size of respectively 216nm, 413nm and 116nm. On a Ti substrate dendritic NPs were obtained with a larger average particle density of 480nm. The influence of the support material on the electrocatalytic activity was tested by means of cyclic voltammetry (CV) for the reduction reaction of benzylbromide (1mM) in acetonitrile+0.1M tetrabutylammonium perchlorate (Bu4NClO4). When the nucleation potential (En) was applied at high cathodic overpotential, a positive shift of the reduction potential was obtained. The nucleation (tn) and growth time (tg) mostly had an influence on the current density whereas longer deposition times lead to larger current densities. For these three parameters an optimum was present. The best electrocatalytic activity was obtained with Ag NPs deposited on Ni were a shift of the reduction peak potential of 145mV for the reaction of benzyl bromide was measured in comparance to bulk silver. The deposition on Au substrate yielded a positive shift of 114mV. There was no indication of an altered reaction mechanism as the reaction was characterized as diffusion controlled and the transfer coefficients were in accordance with bulk silver. There was a beneficial catalitic activity measured due to the interplay between support and NPs. This resulted in a shift of the reduction peak potential of 34mV (Ag NPs on Au) and 65mV (Ag NPs on Ni) compared to Ag NPs on a GC substrate.