Geometric and electronic characteristics of active sites on TiO2-supported Au nano-catalysts: insights from first principles

Abstract

Quantum chemical and ab initio thermodynamic calculations were used to investigate the mechanism of CO oxidation on Au/TiO(2) and the geometric and electronic character of active sites. We show that CO oxidation over Au/TiO(2) might proceed via a two site mechanism with oxygen adsorbing and dissociating at the Au/oxide interface or the perimeter of Au particles and CO adsorbing on Au sites away from the interface. The electronic fingerprint of active Au is a function of external conditions, and it is likely that most Au atoms are populated by CO and electronically neutral. Under highly oxidizing conditions, the Au/oxide interface can accommodate oxygen adsorbates, and these Au atoms will have a cationic fingerprint due to their interaction with oxygen. The choice of precursors used to synthesize catalysts as well as the catalyst preparation and pretreatment procedures significantly affect the electronic characteristics and catalytic activity of Au nano-structures. Based on our first-principles analysis we propose a hypothesis that might help us understand these experimental observations.

Gas‐phase oxidation of 2‐propanol over Au/TiO2 catalysts to probe metal–support interactions

“…The relevance of the Au particle, the Au atoms at the perimeter of the particle, or the interface between the Au particle and the metal oxides are discussed with respect to the possible active sites. Various forms of Au such as metallic gold (Au 0 ) [45,56], oxidized gold species (Au dþ ) [57], the interface between the Au particles and the support [58], or the Au perimeter [59] were suggested as active sites for CO oxidation. Both Au 0 and Au dþ species were also proposed as active sites in methanol oxidation [19,21,24].…”

The critical role of water at the gold-titania interface in catalytic CO oxidation

“…Unlike previous studies, our computational model (SM 2.5 and 2.6) includes both support OH groups and adsorbed water (13,14,18,29). This model substantially simplifies the real system, using a small Au cluster and a single water molecule to represent 3-nm particles and multiple water molecules.…”

Rapid removal and decomposition of gaseous acetaldehyde by the thermo- and photo-catalysis of gold nanoparticle-loaded anatase titanium(IV) oxide

“…catalyze oxidations by dissociating O 2 [29][30][31][32]. Thus, acetaldehyde would be oxidized to acetic acid at the S(Au-Ti) sites (Eqs.…”

“…Oxygen molecule and acetaldehyde are adsorbed at the S(Au-Ti) sites of Au/TiO 2 (step 1) [28][29][30][31][32]. The reaction of acetaldehyde with the adsorbed oxygen affords acetic acid (step 2).…”