CO Self-Promoting Hydrogenation on CO-Saturated Ru(0001): A New Theoretical Insight into How H2 Participates in CO Activation

Dissociation of CO often occurs on Ru surfaces with dense chemisorbed CO (CO*) adlayers, ubiquitous in the practice of catalysis, where the strong bond in CO tends to weaken via bimolecular reactions with H2 before cleavage. Nevertheless, H2 adsorption on CO*-crowded Ru surfaces is a rare event because of the CO*-induced barrier and the competitive adsorption between CO and H2. Here, we thereby performed a comprehensive ab initio study of the coadsorption of CO and H2 as well as the following initiation reaction on Ru(0001). At 100–550 K (3 MPa, H2/CO = 2), Ru(0001) is always saturated, covered by CO with a “hexagonal” pattern, where H2 adsorption is neither kinetically nor thermodynamically favored. On the basis of a systematic analysis of the electronic structure, we find that two adjacent coadsorbed CO* can serve as a promoter for the scission of the H–H bond in H2(g), leading to the simultaneous formation of two COH* molecules in one step (Ea = 1.64 eV). This so-called CO self-promoting hydrogenation ...