The CO oxidation reaction on Rh(111) was studied both at low pressures (e2 × 10 -4 Torr) under steadystate conditions and at high pressures (0.01-88 Torr) in a batch reactor at various gaseous reactant compositions. Surface CO and O coverages were determined using polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and X-ray photoelectron spectroscopy (XPS). CO titration experiments were also carried out on surfaces with known oxygen coverages. Both CO and O inhibition were evident at low pressures so that only within a relatively narrow temperature range were the reaction conditions optimized such that the CO conversion reached ∼20% of the CO flux to the surface. For high pressures and with stoichiometric or slightly oxidizing reactant ratios (O 2 /CO e 2), the reaction fell into three regimes: (i) a CO-inhibited low temperature regime where the reaction rate was determined by CO desorption; (ii) a mass transfer limited regime at high temperatures; and (iii) a transient, high-rate regime lying between regimes (i) and (ii) where the reaction was not completely controlled by mass transfer limitation. For all reaction conditions investigated (when O 2 /CO e 2), the surface oxygen coverage did not exceed ∼0.5 monolayer. With very oxidizing reactants (O 2 /CO g 5), the reactivity of the Rh surface decreased dramatically at high temperatures due to oxidation. Furthermore, the so-called "superior oxide reactivity" for CO oxidation that has been proposed in several recent studies is not evident in this investigation.

A series of mesoporous WO3 catalysts were facilely synthesized by a hydrothermal method using mesoporous silica KIT-6 as a hard template and silicotungstic acid as a precursor.

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A series of MnCo/Cu-ZSM-5 (MnCo/Cu-Z) catalysts with different Mn/Co ratios for the selective catalytic reduction (SCR) of NO with NH3 were prepared by the combination of ion exchange and impregnation. The physicochemical properties of the catalysts were investigated by N2 adsorption/desorption, X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (H2-TPR), X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption of NO x (NO x -TPD) and NH3 (NH3-TPD), and the diffuse reflectance infrared Fourier transform (DRIFT) technique was employed for the detection of intermediate species and the study of the mechanism. The introduction of Mn and Co boosts the catalytic activity of the Cu-Z catalyst at a temperature below 200 °C, and the optimum activity was obtained over the Mn1Co2/Cu-Z catalyst. The enrichment of the high-valent metal ion on the catalyst surface and the improvement in the reducibility of metal oxide are responsible for the elevation in the catalytic activity of MnCo/Cu-Z. The bridged and bidentate modes are the prevailing nitrate species on the Cu-Z and MnCo/Z catalysts, respectively, and both of them were detected over the MnCo/Cu-Z catalyst. Furthermore, the DRIFT spectroscopy (DRIFTS) results indicate that, at 150 °C, the bridged nitrate can react with the adsorbed ammonia species, but the bidentate nitrate fails to do. The SCR reaction over the Cu-Z catalyst follows the Eley–Rideal and Langmuir–Hinshelwood mechanisms simultaneously at 150 °C, whereas an overwhelming dominance of the Eley–Rideal mechanism is identified for the MnCo/Z catalyst. As to the SCR mechanism on the MnCo/Cu-Z catalyst, it combines the features of Cu/Z and Mn1Co2/Z.

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