Influence of benzene on the HUPD and anion adsorption on Pt(110), Pt(111) and Pt(111) electrodes in aqueous H2SO4

We present new results on the influence of C6H6 (ads) on the H-UPD and anion adsorption on the Pt(1 1 0), Pt(1 0 0) and Pt(1 1 1) electrodes in aqueous H2SO4. We study the modification of cyclic-voltammetry (CV)profiles for Pt(1 1 0), Pt(1 0 0) and Pt(1 1 1) brought about by C6H6 (ads) and examine the inhibition of H-UPD and anion adsorption. The results demonstrate that as long as C6H6 is present in aqueous H2SO4, the H-UPD and anion adsorption is suppressed. Repetitive cycling of the C6H6 (ads)-modified Pt(1 1 0) or Pt(1 1 1) electrode in a benzene-free aqueous H2SO4 leads to a partial recovery of the CV profile characteristic of the H-UPD and anion adsorption. However, cycling of the C6H6 (ads)-modified Pt(1 0 0) electrode in a benzene-free aqueous H2SO4 does not affect the CV profile, whose features point to a continuous inhibition of the H-UPD and anion adsorption. The results indicate that the bond between C6H6 (ads) and Pt(1 0 0) is stronger than that between C6H6 (ads) and Pt(1 1 0) or Pt(1 1 1). Cathodic polarization of the C6H6 (ads)-modified Pt(1 1 0), Pt(1 0 0) and Pt(1 1 1) electrodes in benzene-free aqueous H2SO4 leads to reductive desorption Of C6H6 and recovery of the CV features characteristic of clean and well-defined surfaces. (c) 2004 Elsevier Ltd. All rights reserved.