Influence of benzene on the HUPD and anion adsorption on Pt(1 1 0), Pt(1 0 0) and Pt(1 1 1) electrodes in aqueous H2SO4

We present new results on the influence of C6H6 ads on the HUPD 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 HUPD and anion adsorption. The results demonstrate that as long as C6H6 is present in aqueous H2SO4, the HUPD 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 HUPD 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 HUPD 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.