A Raman spectroelectrochemical study of potential-controlled benzenethiol desorption from Pt–Fe group alloy films

Abstract

A combination of in situ Raman spectroelectrochemistry and cyclic voltammetric (CV) stripping methods is used to study the adsorption/desorption of benzenethiol (BT) at platinum (Pt) alloy electrodes. The data from both methods confirm that alloying Pt with Fe group metals enhances the sulfur tolerance of the alloy over Pt. The Raman signal of BT adsorbed at electrodeposited films of Pt3Co and Pt4Ni diminishes to a greater extent after only one oxidation/reduction cycle than that observed for BT adsorbed at pure Pt films. Oxidatively desorbed BT readsorbs at Pt3Co at a potential that is ∼50 mV lower than that at which it readsorbs at either Pt or Pt4Ni films, further demonstrating its enhanced sulfur tolerance. Sulfate bands are absent from the spectra of all films, indicating that the metal–S bonds that form upon adsorption are broken during oxidative removal of BT rather than cleavage of C–S bonds in the BT adsorbate. The CV stripping data confirm that BT is more readily electrochemically stripped from the alloy films than from pure Pt films. The combination of Raman spectroelectrochemistry and CV stripping enables more comprehensive characterization of sulfur-tolerant electrocatalyst surfaces in situ, under electrochemical conditions.