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

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.

► Raman spectroelectrochemistry is used to study sulfur tolerance of Pt–Co/Ni alloys.
► Raman spectra show that BT readsorbs to Pt3Co at lower potentials.
► Less BT readsorbs to Pt3Co than to Pt4Ni or to Pt alone.
► In all films, BT desorbs through the breaking of the metal-S bond.
► Cyclic voltammetry agrees with Raman data that Pt3Co is the most resistant alloy.