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

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 + Oads → 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.