Theoretical Study of Pt Cocatalyst Loading on Anatase TiO2(101) Surface: From Surface Doping to Interface Forming

For photocatalytic water splitting, the loading of noble metal particles as cocatalyst is a very crucial step. It can speed up the reaction rate or even change the reaction pathway. However, for the modification mechanism of Pt cocatalyst, the consistent conclusions and effective theoretical support are not yet completely established at present, especially the growth mechanism and the microstructure of the interface. For this purpose, the overall evolutionary process of Pt cocatalyst loading on an anatase TiO2(101) surface and the related microstructure and properties were systematically investigated, using a combination computational method of density functional theory calculations and Monte Carlo simulations. With the increase of loading amount, the growth of Pt cocatalyst sequentially experiences the following stages: surface doping, cluster nucleating, cluster loading, one-dimensional nanowire loading, two-dimensional nanowire grid loading, ultrathin film ripening, and film forming via the layer-by-layer mode. Finally, the microstructure of the interface constructed by the Pt(111) surface and the anatase TiO2(101) surface is determined by structural characteristics and lattice match. The interfacial properties, such as built-in electric field, band bending, and Schottky barrier, were further estimated and analyzed. On the basis of the calculated results, it can be concluded that Pt cocatalyst loading can not only suppresses the recombination of photogenerated electronhole pairs but also promotes the absorption of visible light due to the surface plasmon resonance effect. This detailed study may provide further insight into the mechanism of Pt cocatalyst loading and elucidate the reactions that occur on the surfaces of Pt/TiO2 composite photocatalyst.