Existence of the Coadsorbed Phase of the CO Intermediates under CO ₂ Activation with Hydrogen on Ru(0001)

The mechanism for CO 2 activation on the Ru(0001) surface, the dominant surface of catalytic Ru nanoparticles, was elucidated using operando ambient-pressure X-ray photoelectron spectroscopy in CO 2 /H 2 . At 300 K, the major reaction was CO 2 dissociation, generating CO adsorbates at both atop and bridge sites (CO t * and CO b *, respectively). The appearance of such a coadsorbed phase of CO t * and CO b * was reproduced by density functional theory calculations. At 370–470 K, these CO* species were converted to elemental carbon. Because the reaction condition matched the temperature ranges of the CO 2 methanation on the Ru-based catalysts, CO t * and CO b * coadsorbed specifically at the interface between Ru(0001) and CO 2 /H 2 gases seem to be the critical factor for elucidating the reaction mechanism.