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

• Published in: Nanomaterials (Basel, Switzerland) Vol. 10; no. 5; p. 880
• Main Authors: Pakrieva, Ekaterina, Kolobova, Ekaterina, Kotolevich, Yulia, Pascual, Laura, Carabineiro, Sónia A C, Kharlanov, Andrey N, Pichugina, Daria, Nikitina, Nadezhda, German, Dmitrii, Partida, Trino A Zepeda, Vazquez, Hugo J Tiznado, Farías, Mario H, Bogdanchikova, Nina, Cortés Corberán, Vicente, Pestryakov, Alexey
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 02-05-2020; MDPI AG
• Subjects: gold active sites; gold catalysts; gold electronic state; metal content; n-octanol oxidation; support modifiers; metal content; selectivity; support modifiers; DFT; gold active sites; gold catalysts; gold electronic state; n-octanol oxidation; acid-base centers; solvent adsorption; pretreatment atmosphere
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano10050880

This study aims to identify the role of the various electronic states of gold in the catalytic behavior of Au/M
O
/TiO
(where M
O
are Fe
O
or MgO) for the liquid phase oxidation of
-octanol, under mild conditions. For this purpose, Au/M
O
/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.