Absorbed sulfur has been implicated in the reduction of the catalytic activity of Pt nanoparticles (NPs), yet it has also been shown to promote the activity of Pt as a site-modifier in formic acid, formaldehyde, and methanol electro-oxidation. These contradictory observations could be explained through better understanding of the exact chemical state of adsorbed S.

YuYe Tong and co-workers, Georgetown University, USA, have performed electrochemical studies of S adsorption on commercial carbon-supported Pt (Pt/C) and Pt black (Pt–B) NPs. By combing electrochemistry and surface enhanced Raman scattering experiments with discrete Fourier transform (DFT) calculations, the team has shown for the first time that the chemical state of S_ads on Pt NP surfaces is a sulfide (S^2–).

Different S partition patterns were seen, depending on the adsorption or desorption process. This will have important ramifications for prevention of sulfur poisoning of metals NPs.

• Chemical State of Adsorbed Sulfur on Pt Nanoparticles
  I.-S. Park, B. Xu, D. O. Atienza, A. M. Hofstead-Duffy, T. C. Allison, Y. Y. J. Tong,
  ChemPhysChem 2011.
  DOI: 10.1002/cphc.201000998