X-ray photoelectron spectroscopy of oxygen-containing layers formed by a linear potential scan on stepped gold (111) films in aqueous 1 M sulphuric acid

Abstract

X-ray photoelectron spectroscopy (XPS) data of oxygen-containing layers (O-layers) made on stepped gold (111) film electrodes from aqueous 1 M sulphuric acid by single linear potential scans at 0.10 V s − 1 and 298 K are reported. The potential scan covered from the open circuit potential to anodic switching potential E as = 2.50 V versus normal hydrogen electrode (NHE) and holding times at E as in the range 30–300 s. The anodic charge density q a determined from the oxidation and reduction voltammetric scan is in the range 0.20 ≤ q a ≤ 2.5 mC cm − 2 . For the potential E = 0.5 V, in the absence of O-layers, the S 2p core level spectrum indicates the presence of sulphate/bisulphate adsorbates. For E as > 1.3 V, the O 1s core level spectrum involves the contribution from water, OH- and O-species. These spectra are deconvoluted utilising either three or four Gaussian contributions with values of peaked binding energy and full width at half-maximum height (FWMH) in good agreement with expectations. The envelope of these XPS O 1s signals after correction for the contribution of sulphate/bisulphate adsorbates and adventitious carbon approaches the XPS signal that has been reported for the core level spectrum in the O 1s region of oxidised gold surfaces produced by laser pulses at different molecular oxygen pressures. The O/OH concentration ratio in the O-layer increases with E as ageing time t ag and cathodic charge density q c. The hydrous nature of the O-layer, evaluated through the analysis of the core level spectra in the O 1s region, decreases as E as and t ag are increased. Results are interesting to unravel the composition and structure of electrochemically grown O-layers at the surface of the gold substrate, and the influence of the history of these O-layers on the respective XPS features.