Spontaneous Deposition of Ag. Influence of Composition of Ag-Containing Solution on the Electrocatalytic Activity of Pt-Modified Surface

Abstract

Using spontaneous and electrochemical deposition of Ag, Ag-covered Pt polycrystalline electrodes were prepared. The behavior of these Pt-based composite catalysts depends on their morphology, the crystalline and electronic properties, and in a minor extent, the solution composition containing Ag ion. This work deals with the study of methanol and carbon monoxide electrooxidation using Pt surfaces modified by Ag through spontaneous deposition. The main objective is to investigate the influence of the counterion nature of Ag-containing electrolytic solutions. For this purpose, the electrooxidation of methanol adsorbed residues and also of carbon monoxide was studied applying conventional electrochemical methods in aqueous 1 M H 2 SO 4 . Those reactions exhibit different behavior which is highly dependent on the nature of the Ag-containing electrolytic solution used to carry out the deposition process. The results demonstrate that in the adsorption process of both methanol residues and carbon monoxide, the interaction with Pt surface is achieved through electrodeposited Ag, but the counterion plays a significant role. A theoretical model is proposed in which it is considered the coadsorption of the counterion with water molecules preadsorbed on Pt surface and the interaction of the anions with residues adsorbed from carbon monoxide and methanol.

Hydrothermal synthesis of Pt–Ag alloy nano-octahedra and their enhanced electrocatalytic activity for the methanol oxidation reaction

“…The magnified TEM images (inset c) and EDX mapping patterns (insert d) show that these small-size nanocrystals are the Pt-Ag alloy cuboctahedra. The previous report has demonstrated that the Ag + ion can undergo under potential deposition (UPD) on the Pt surface, 32,33 which decreases the Gibbs free energy of Ag + reduction. Thus, Ag + ions liberated from AgCl at high temperature can be reduced by HCHO and deposit preferentially on the Pt nuclei surface according to the thermodynamic viewpoint.…”