Geometric stability and reaction activity of Pt clusters adsorbed graphene substrates for catalytic CO oxidation

Abstract

The geometric stabilities, electronic structures and catalytic properties of tetrahedral Pt₄ clusters anchored on graphene substrates are investigated using the first-principles methods. It is found that the small Pt₄ clusters adsorbed on pristine graphene substrates easily interconvert between structural isomers by the small energy barriers, while the structural interconversion of Pt₄ clusters on the defective graphene and oxygen-doped graphene (O-graphene) have the large energy barriers. Compared to other graphene substrates, the Pt₄ clusters supported on the O-graphene substrate (Pt₄/O-graphene) have the least geometrical distortion and the high symmetry of the Pt₄ cluster can enhance the sensitivity of reactive gases. Moreover, the sequential reactions of CO oxidation on Pt₄/O-graphene are investigated for comparison. Compared with the coadsorption reaction of CO and O₂ molecules, the dissociative adsorption of O₂ as a starting step has a small energy barrier (0.07 eV) and is followed through the Eley–Rideal reaction with an energy barrier of 0.42 eV (CO + O_ads → CO₂). The results provide valuable guidance for fabricating graphene-based catalysts as anode materials, and explore the microscopic mechanism of the CO oxidation reaction on atomic-scale catalysts.