A First-Principles Study of Carbon-Oxygen Bond Scission in Multiatomic Molecules on Flat and Stepped Metal Surfaces

Step sites over terrace sites have been suggested to be the active sites in many catalytic reactions particularly bond breaking of diatomic molecules. Aiming to provide insight into the role of step sites in multiatomic molecules bond breaking reactions and their dependence on catalysts, we present herein a systematic first-principles study of carbon-oxygen bond scission of diatomic CO and multiatomic HCO and CH3HCO on flat and stepped Co, Rh, and Ir surfaces. We find that multiatomic molecules exhibit distinct carbon-oxygen scission activity from diatomic molecules regardless of the metal catalysts (Co, Rh, and Ir) considered: compared to the huge enhancement of step sites for CO with a barrier 0.81-1.29 eV lower than that of flat surfaces, the role of step sites for CH3CHO is substantially weakened with a barrier 0.11-0.27 eV higher than that of flat surfaces. The reason for this is the change of adsorption configurations on flat surfaces and increase of Pauli repulsion on the congested stepped sites for the dissociation of multiatomic molecules.