Bandgap engineering of SrTiO3 /NaTaO3 heterojunction for visible light photocatalysis

Hybrid density functional of HSE06 has been adopted to investigate the geometry and electronic properties of SrTiO3/NaTaO3 heterostructures in contrast with the cubic SrTiO3 and cubic NaTaO3. The SrTiO3/NaTaO3 heterostructures with varied monolayers of SrTiO3 and NaTaO3 units are constructed, and all the heterojunction systems have the smaller bandgaps as compared with those of pure SrTiO3 and NaTaO3. For the (SrTiO3)m/(NaTaO3)n (m + n = 10) systems, the bandgap decreases in the order of m = 1, 2, 3, 4, 5, while the bandgap increases in the order of m = 5, 6, 7, 8, 9. We also investigate the (SrTiO3)m/(NaTaO3)m systems (m = 1, 2, 3, 4, 5, 6, 7), and the calculated results suggest that the (SrTiO3)6/(NaTaO3)6 system has the smallest bandgap of 2.58 eV in our considered systems. This study indicates the development of SrTiO3/NaTaO3 heterojunction is a promising way to improve the photocatalytic activities of SrTiO3 and NaTaO3.