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

Abstract

The effects of various heterocyclic coadsorbates (pyridine, pyrazine, 2,2′‐bipyridyl, 4,4′‐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 heteroatom significantly hinder both the silver underpotential (UPD) and bulk deposition processes giving rise to a diminution in the underpotential shift in the former and an overpotential in the latter. The diminution of the underpotential shift suggests a strong interaction of the adsorbate adlayer with the platinum substrate. In addition, the existence of a significant overpotential necessary for initiation of bulk silver deposition suggests a significant interaction between the UPD silver monolayer and the adsorbate adlayer. A Pt/Ag/adsorbate intermediary structure is proposed based on this voltammetric evidence. The sulfur‐containing adsorbates completely inhibit silver UPD as well as the formation of a normalPtO film on the polycrystalline electrode. The only observable processes were bulk deposition (at overpotentials of the order of 125 mV) and subsequent bulk stripping of the deposited 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.

A comparative electrochemical study of electrosorbed 2- and 4-mercaptopyridines and their application as corrosion inhibitors at C60 steel

“…Up-to-date, results of most investigations suggest that mercaptopyridines bond to the surface through S-atom after cleavage of the S-H bond and formation of a metal-S bond. [12][13][14][15][16][17][18][19][20] However, it has been suggested also that mercaptopyridines might bind to the gold surface through its N-atom. 21 Corrosion of pipes, pumps, turbine blades, coolers, superheaters, reheaters, fuel cells, and exhaust systems cause enormous industrial losses due to production downtime, accidental injuries, and replacement costs.…”

Effects of Mercaptopyridines on the Underpotential and Overpotential Deposition of Copper on Pt(111)

“…Platinum, 11 gold, 12 and silver 4 electrodes pretreated with organic adsorbates, e.g., mercaptans and aromatic carbon and nitrogen, not only inhibit copper 12,13 and silver 6,14 underpotential deposition (upd) but also delay the onset of bulk deposition. In fact compounds such as mercaptopyridines are able to displace copper and silver monolayers 8,14 deposited on these electrodes.…”

“…Although this is their best known application, these films can also be used as corrosion inhibitors or for the construction of nanostructure-based devices among other uses. Aromatic thiols have been studied on Ag(111), Pt(111), , and Au , by surface-enhanced Raman scattering (SERS) , electron energy loss spectroscopy (EELS), low-energy electron diffraction (LEED), Auger spectroscopy, and electrochemical methods. , The behavior generally accepted for both aliphatic and aromatic thiol compounds on these metals is that they form an ordered layer on the metallic surface, in which the molecules are bound through the S atom upon breakage of the S−H bond and formation of the metal−S bond.…”

Influence of Organic Adsorbates on the Under- and Overpotential Deposition of Copper on Gold Electrodes

“…On the other hand the adsorption of numerous organic species on Au [28][29][30][31][32][33][34][35][36][37][38][39][40][41] and on platinum electrodes [18,19] has been investigated showing that they are able to hinder or even inhibit the deposition of copper and silver on platinum substrates [20,21].…”