Elucidation of Active Sites of Gold Nanoparticles on Acidic Ta₂O₅ Supports for CO Oxidation

Abstract

Gold nanoparticles of small sizes with a highly uniform dispersion were successfully deposited on several crystalline forms of Ta 2 O 5 (pseudohexagonal, orthorhombic, and pyrochlore) by the sol immobilization method. The pseudohexagonal Ta 2 O 5 (TT-Ta 2 O 5 ) synthesized by a hydrothermal method showed the highest catalytic activity for CO oxidation as a support for gold catalysts. The temperature at 50% CO conversion was −11 °C for 1 wt % Au/ TT-Ta 2 O 5 , and the temperature was 23 °C at 100% CO conversion (space velocity of 20000 mL h −1 g cat −1). To investigate the reaction mechanism, in situ diffuse reflectance infrared Fourier transform spectroscopy for Au/TT-Ta 2 O 5 was performed, and the sequential delivery of adsorbed CO on Ta 2 O 5 sites and Au sites to the active sites was observed at −120 °C. The results of temperatureprogrammed CO reduction suggested that the oxygen adsorbed at −100 °C contributed mainly to the high catalytic activity of CO oxidation, while the lattice oxygen played a minor role for CO oxidation from −60 to 100 °C, which was the same temperature range with the actual reaction condition.

Defective NiO as a Stabilizer for Au Single-Atom Catalysts

“…Based on the Au nanoparticles is the face-centered cubic (fcc) structure, and the deposited Au nanoparticle is supposed to be a hemisphere (see the Supporting Information for details). 33…”

Au3+ Species Boost the Catalytic Performance of Au/ZnO for the Semi-hydrogenation of Acetylene

“…As a rule, the blue shift in frequency suggests electron-deficient species relative to metallic Au 0 , that is, positively charged Au sites . According to previous reports, the bands at ∼2120 and 2150 cm –1 could be attributed to Au δ+ (1 > δ > 0) and Au + , respectively. ,,− For Au/ZnO-D–O, two bands were detected at ca. 2100 and 2150 cm –1 , which were attributed to Au 0 and Au + , respectively.…”

Praseodymia–titania mixed oxide supported gold as efficient water gas shift catalyst: modulated by the mixing ratio of oxides

“…6(d) ). 37 The CO adsorbed on Pr a Ti b O x also shows the band at 2122 cm −1 , after loading Au on it (Au/Pr a Ti b O x ), the peak intensity further increased indicates it is overlapped with the CO–Au δ + band. Fig.…”

“…Then N 2 gas was introduced at −180 °C with a flow rate of 50 mL min −1 for 30 min to fully exclude the gas phase and weakly adsorbed CO species. 36–38…”

“…Then N 2 gas was introduced at À180 C with a ow rate of 50 mL min À1 for 30 min to fully exclude the gas phase and weakly adsorbed CO species. [36][37][38] To be noted most of the characterizations are done for the spent catalyst in order to more precisely reecting the properties of catalysts especially under steady-state conditions. According to McFarland and Metiu, heterogeneous catalytic reactions are run under steady-state conditions instead of at equilibrium.…”