Effects of Organic Adsorbates on the Underpotential and Bulk Deposition of Silver on Polycrystalline Platinum Electrodes.

摘要

The effects of various heterocyclic co-adsorbates (pyridine, pyrazine, 2,2'-bipyridyl, 44,4'-bipyridyl, 4-phenylpyridine, 4-mercaptopyridine, and 2-mercaptopyridine) on the electrodeposition of silver onto Polycrystalline platinum electrodes in 0.10M H2SO4 have been studied using cyclic voltammetry. Adsorbates bonding through a nitrogen hetero-atom significantly hinder both the silver underpotential (UPD) and bulk deposition processes. The existence of a Pt/Ag/adsorbate structure is proposed based on the significant overpotential necessary to initiate bulk deposition. The sulfur-containing heterocycles completely inhibit silver UPD as well as the formation of a PtO film on the polycrystalline electrode. The only observable processes were bulk deposition (at overpotentials on the order of 125m V) and subsequent bulk stripping of silver. The effects of having a polycrystalline surface have been assessed by comparing these results to those from studies of silver deposition onto Pt(111) surfaces in the presence of the same coadsorbed species.