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