CO adsorption and hydrogenation on crystalline YBa₂Cu₃O_x. Thin films

YBa₂Cu₃O_x (YBCO, x=6-7) is shown to have catalytic activity for methanol synthesis from syngas in this work. In order to get more details about the nature of the reactive site and reaction mechanism, CO adsorption and hydrogenation on a high quality YBCO thin film were studied by using in situ Fourier transform infrared spectroscopy (FTIR), angle-resolved X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). Carbonate-like species, aldehyde, formate and methoxy were detected as reaction intermediates. After the CO hydrogenation reaction Cu²⁺ ions were reduced to Cu^l+, and the orthorhombic structures of YBCO was transformed to the tetragonal phase with the formation of carbonatelike complexes. The degradation of some YBCO to amorphous surface phases was also observed. Based on these studies, carbonate-formate-dioxymethylene-methoxy (or carbonate-aldehyde-carnene-methane) reaction scheme is proposed.