Carbon Monoxide Oxidation by Polyoxometalate‐Supported Gold Nanoparticulate Catalysts: Activity, Stability, and Temperature‐ Dependent Activation Properties

Abstract

Nanoparticulate gold supported on a Keggin-type polyoxometalate (POM), Cs [α-SiW O ]⋅n H O, was prepared by the sol immobilization method. The size of the gold nanoparticles (NPs) was approximately 2 nm, which was almost the same as the size of the gold colloid precursor. Deposition of gold NPs smaller than 2 nm onto POM (Au/POM) was essential for a high catalytic activity for CO oxidation. The temperature for 50 % CO conversion was -67 °C. The catalyst showed extremely high stability for at least one month at 0 °C with full conversion. The catalytic activity and the reaction mechanism drastically changed at temperatures higher than 40 °C, showing a unique behavior called a U-shaped curve. It was revealed by IR measurement that Au was a CO adsorption site and that adsorbed water promoted CO oxidation for the Au/POM catalyst. This is the first report on CO oxidation utilizing Au/POMs catalysts, and there is a potential for expansion to various gas-phase reactions.

Importance of Size and Contact Structure of Gold Nanoparticles for the Genesis of Unique Catalytic Processes

“…However, the acidity is controlled by changing the countercations, and NPs were successfully deposited on Cs 4 [α-SiW 12 O 40 ]· n H 2 O (Cs–SiW) by SI using thiolate-protected Au NPs. The obtained Au(2.0)/Cs–SiW (2.0 indicating that Au colloids of 2 nm in size were used for SI) exhibited high catalytic activity for low-temperature CO oxidation, and the T 1/2 was surprisingly low (−67 °C) . The light-off curve for CO conversion by Au(2.0)/Cs–SiW was a U-shaped curve (Figure ), as observed for Au/SiO 2 and for Au/Mg­(OH) 2 : the conversion increased from −80 to 40 °C, markedly decreased as the temperature was increased to 100 °C, and then gradually increased again at higher temperatures (>120 °C).…”

“…The values in parentheses in the sample names indicate the particle size of thiolate-protected Au colloids used for SI. Reaction conditions: catalyst, 0.15 g; 1 vol % CO in air (50 mL min –1 ); SV, 20,000 mL h –1 g cat –1 . Reproduced with permission from ref .…”

Highly efficient base-free aerobic oxidation of alcohols over gold nanoparticles supported on ZnO-CuO mixed oxides

“…Inspired by pioneering work of Haruta et al [7] and Hutchings et al [8], the catalytic performance and reaction mechanism of gold catalysts have been comprehensively studied for more than 30 years. Gold catalysts have displayed extraordinarily high catalytic performance for a great deal of reactions [9][10][11][12][13]. As reported in the literature, the catalytic activity of gold catalysts is highly related to the size of gold [14], the type of support [15], and the interaction between gold and support [16].…”

Synthesis and performance of solid proton conductor molybdovanadosilicic acid

“…1,2 During the past decades, HPAs have attracted huge interest owing to their huge potential in many elds, for instance, catalysts, biomedicine and material science. [3][4][5][6][7] In particular, due to their high proton conductivity and proton transfer/storage abilities, HPAs have become one of the best candidate electrolyte materials for the development of fuel cells and supercapacitors. [8][9][10][11][12] So, a further investigation of the role and function of these compounds in electrochemical devices will give insight into developing solid electrolytes based on HPAs.…”