Effect of Gold Electronic State on the Catalytic Performance of Nano Gold Catalysts in -Octanol Oxidation.

This study aims to identify the role of the various electronic states of gold in the catalytic behavior of Au/MO/TiO (where MO are FeO or MgO) for the liquid phase oxidation of -octanol, under mild conditions. For this purpose, Au/MO/TiO catalysts were prepared by deposition-precipitation with urea, varying the gold content (0.5 or 4 wt.%) and pretreatment conditions (H or O), and characterized by low temperature nitrogen adsorption-desorption, X-ray powder diffraction (XRD), energy dispersive spectroscopy (EDX), scanning transmission electron microscopy-high angle annular dark field (STEM HAADF), diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy of CO adsorption, temperature-programmable desorption (TPD) of ammonia and carbon dioxide, and X-ray photoelectron spectroscopy (XPS). Three states of gold were identified on the surface of the catalysts, Au, Au and Au, and their ratio determined the catalysts performance. Based on a comparison of catalytic and spectroscopic results, it may be concluded that Au was the active site state, while Au had negative effect, due to a partial blocking of Au by solvent. Au also inhibited the oxidation process, due to the strong adsorption of the solvent and/or water formed during the reaction. Density functional theory (DFT) simulations confirmed these suggestions. The dependence of selectivity on the ratio of Brønsted acid centers to Brønsted basic centers was revealed.