Poisoning of Pt3Co Electrodes: A Combined Experimental and DFT Study

Density functional theory calculations and rotating ring disk electrode experiments were performed to investigate the poisoning effects of sulfur species on the catalytic properties of elemental Pt and Pt3Co alloy surfaces. Experimental data indicates that there is a positive shift in the oxidation overpotential of Pt3Co accompanied by less oxidation/reduction cycles necessary in rotating ring disk electrode experiments (RRDE) in order to remove most of the sulfur species. Our theoretical calculations suggest that OH clustering is substantially reduced on the Pt3C(111) surface irrespective of the presence of Co atoms versus Pt(111). While the presence of Co does enhance adsorption of electronegative atoms/molecules on neighboring Pt sites, once Co atoms are oxidized or a Co−S bond is formed, they serve as a pin for the poison and subsequently reduce bonding of additional electronegative atoms/molecules at nearby sites. Additionally, our calculations indicate that a combination of effects due to less Pt3Co surface oxidation, more weakly adsorbed S species, and lower reaction barriers for SO2 oxidation on Pt3Co versus Pt subsequently leads to easier cleaning of the surface.