Dispersion and site-blocking effect of molybdenum oxide for CO chemisorption on the Pt(1 1 0) substrate

The Pt(1 1 0) model surfaces modified by the metallic molybdenum and by the MoOx (molybdenum oxide species) were fabricated via thermal decomposition of Mo(CO)6 and subsequent oxidation on a clean Pt(1 1 0) substrate, by means of Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), as well as high-resolution electron-energy-loss spectroscopy (HREELS). CO chemisorption on these model surfaces was investigated using thermal desorption spectroscopy (TDS) and HREELS. The presence of the metallic molybdenum and MoOx species suppresses CO chemisorption on the Pt(1 1 0) substrate, indicating a physically site-blocking effect. The electron-deficiency of the Pt(1 1 0), due to the modification of metallic molybdenum, causes the low-temperature peak of CO desorption to shift downward in temperature by ∼30 K. The interaction between the MoOx and the underlying Pt(1 1 0) substrate has no influence on CO desorption temperature.

Scheme of CO chemisorption on the Mo/Pt(1 1 0) and MoOx/Pt(1 1 0) model surfaces is illustrated as follows. The presence of the metallic molybdenum and MoOx species suppresses CO chemisorption on the Pt(1 1 0) substrate, indicating a physically site-blocking effect. However, the interaction between the MoOx and the underlying Pt(1 1 0) substrate has no influence on CO desorption temperature.Figure optionsDownload as PowerPoint slide