Comparison studies of interfacial energetic and electronic properties of bimetallic AuCu/TiO2 hetero-structures from DFT calculations

Abstract

Bimetallic AuCu/TiO₂ composites have been extensively studied because of their excellent modification effects in photocatalysis. The present work investigated the interfacial energetic and electronic structures of AuCu/TiO₂, Au/TiO₂ and Cu/TiO₂ hetero-structures using first-principles calculations. Calculation results of interfacial structures show that the interface spacings and interfacial formation energies of AuCu/TiO₂ hetero-structures are generally smaller than those of the Au/TiO₂ hetero-structure. Calculation results of electronic structures indicate that AuCu/TiO₂ hetero-structures have more pronounced interfacial states than the Au/TiO₂ hetero-structure due to the stronger interaction of the AuCu layer with the TiO₂ substrate. Meanwhile, the amount of charge transfer across the AuCu/TiO₂ interfaces is larger than that across the Au/TiO₂ interface. Furthermore, the Schottky barrier heights of AuCu/TiO₂ hetero-structures are smaller than that of the Au/TiO₂ hetero-structure, which promotes electron transfer from the TiO₂ substrate to the AuCu layer. These results demonstrate that the modification effects of bimetallic AuCu, in which some Au atoms are replaced with Cu atoms, not only enhance the interaction of the metal layer with the TiO₂ substrate, but also promote the separation of photo-generated electron–hole pairs in TiO₂. This detailed study may provide further insight into the underlying photocatalytic mechanism of AuCu/TiO₂ composite photocatalysts.