DRIFTS-QMS Study of Room Temperature CO Oxidation on Au/SiO₂ Catalyst: Nature and Role of Different Au Species

Abstract

The nature and role of different Au species on a Au/SiO 2 catalyst in room temperature (rt) CO oxidation have been studied by operando diffuse reflectance infrared spectroscopy (DRIFT) coupled with quadruple mass spectrometry (QMS). It has shown that different pretreatments (oxidative and reductive) of Au/SiO 2 have a significant effect on the nature of Au species and thus the CO oxidation performance. High temperature (500°C) O 2 -treatment leads to cationic Au species which is inactive for rt CO oxidation. Reductive treatment (either H 2 or CO) results in metallic Au species that are immediately active for rt CO oxidation. Furthermore, CO oxidation activity is found in good correlation with the reduction degree of Au species, a clear indication of the essential role of metallic Au species played in rt CO oxidation. The accompanying slight deactivation with the oxidation of metallic Au species on reductively treated Au/SiO 2 in CO oxidation suggests that cationic Au species may play a negative role in rt CO oxidation. The effect of water in rt CO oxidation on Au/SiO 2 was also investigated. Two positive roles played by water in CO oxidation have been identified: activation of O 2 and assistance the reduction of cationic Au species.

Development of novel supported gold catalysts: A materials perspective

“…Third, we have established some correlations between structure and function by means of systematic characterization, although these correlations have not been summarized in detail here. Last but not least, the development of these gold catalysts has provided new opportunities for further fundamental and applied research [130,131,146,186,188,220,[275][276][277][278]. For instance, the development of Au/SiO 2 [75,76] and Au/FePO 4 [86] catalysts makes it possible to study the nature of active sites and reaction mechanisms [130,131,146], and the development of Au/Al 2 O 3 /TiO 2 [71] and SiO 2 /Au/TiO 2 [77,84] catalysts prompted the subsequent DFT studies [186,220].…”

“…Wu et al conducted a detailed FTIR study of CO oxidation on Au/fumed SiO 2 [130,131]. They found that the thermal treatment of Au/SiO 2 in O 2 resulted in the formation of gold nanoparticles on the SiO 2 support, as demonstrated by TEM.…”

“…Reproduced by permission of Elsevier from Ref. [76] 7 water or hydroxyl groups can activate oxygen and facilitate the reduction of cationic gold species [130,131]. This work is relevant, because it is based on very active, rather than not-so-active, Au/SiO 2 catalysts.…”

Synthesis of Gold Catalysts Supported on Mesoporous Silica Materials: Recent Developments

“…After 100 min of reaction, the 0.7% Au/SBA-15-CeO 2 catalyst showed high catalytic activity (100% lactose conversion) and a 100% selectivity towards LBA, when it was used at a catalyst/lactose ratio of 0.2 under alkaline (pH 9.0) and mild reaction temperature (65 °C). [129,[133][134][135][136][137][138][139] and bimetallic [140][141][142][143] gold catalysts supported amorphous SiO 2 , as well as for the preparation of Au/SiO 2 -based catalysts [136], has demonstrated that amorphous silica can be also employed as a support to prepare active Au/SiO 2 catalysts. Although this synthesis method has not been intensively investigated, it can be regarded as highly efficient for the preparation of gold catalysts supported on MSM.…”

“…Although this synthesis method has not been intensively investigated, it can be regarded as highly efficient for the preparation of gold catalysts supported on MSM. However, it should be noted that the [Au(en) 2 ]Cl 3 precursor must be kept protected from light to prevent its decomposition [129,[133][134][135][136][137][138][139].…”