Structure of Au(111) and Au(100) single-crystal electrode surfaces at various potentials in sulfuric acid solution determined by in situ surface X-ray scattering

Kondo, Toshihiro*; Morita, Jun*; Hanaoka, Kazuya*; Takakusagi, Satoru*; Tamura, Kazuhisa   ; Takahashi, Masamitsu; Mizuki, Junichiro; Uosaki, Kohei*

Potential-dependent surface structures of Au(111) and Au(100) single-crystal electrodes in a 50 mM HSO solution were investigated at an atomic level using in situ surface X-ray scattering (SXS) techniques. It was confirmed that both the Au(111) and Au(100) surfaces were reconstructed with an attached submonolayer of an oxygen species, most probably water, at 0 V (vs Ag/AgCl). Results at +0.95 V supported a previously suggested model for both the Au(111) and the Au(100) electrodes that, based on infrared and scanning tunneling microscopy measurements, the surfaces were a (11) structure with the coadsorbed sulfate anion and hydronium cation (HO). At +1.05 V, where a small amount of an anodic current flowed, adsorption of a monolayer of oxygen species was observed on both surfaces.