Effect of surface oxygen vacancy on pt cluster adsorption and growth on the defective anatase TiO2(101) surface

The effect of surface oxygen vacancies on the adsorption and clustering of the Pt adatoms over the defective anatase TiO2(101) surface has been studied using density functional theory slab calculations. The surface oxygen vacancy site was found to be the most active site for a single Pt adatom with an adsorption energy of 4.87 eV. As such, this site may act as a nucleation center for particle growth on the defective anatase TiO2(101) surface. The pathways for forming the two stable Pt-2 adsorption configurations from a single Pt adatom in the oxygen vacancy site and another from the neighboring bridging 2cO sites involve the diffusion of the second Pt adatom out of the bridging 2cO site. The transition states for the dimer formation were located at Pt adatom diffusing out of the bridging 2cO site. Furthermore, we found that the bond-breaking step determines the barrier height for the Pt adatom diffusion, which is similar to 1 eV. Among five stable Pt-3 adsorption structures at the oxygen vacancy site on the defective anatase TiO2(101), the most stable structure is triangular with all three Pt atoms interacting directly with the surface atoms. The possible pathways for Pt adatom diffusion to form the most stable Pt3 configuration were analyzed. The barriers for Pt adatom diffusion in Pt3 formation were predicted to be similar to that of the Pt2 formation due to similar transition state structures. The barrier height indicates that clustering will be kinetically hindered at low temperature.