Highly Efficient and Selective Oxidation of Ethanol to Acetaldehyde by a Hybrid Photocatalyst Consisting of SnO2 Nanorod and Rutile TiO2 with Heteroepitaxial Junction

Single-crystal SnO2 nanorods were grown on rutile TiO2 with a heteroepitaxial relation of SnO2{001}/TiO2{001} (SnO2-NR#TiO2) by a hydrothermal reaction. Resulting compressive lattice strain in the SnO2-NR near the interface induces a continuous increase in the a-axis length extending over 60 nm to relax towards the [001] direction from the root to the tip. UV-light irradiation of the robust SnO2-NR#TiO2 stably progresses the selective oxidation of ethanol to acetaldehyde with an external quantum yield of 25.6 % at excitation wavelength (lambda(ex))=365 nm under ambient temperature and pressure. Spectroscopic analyses and density functional theory simulation results suggested that the extremely high photocatalytic activity stems from the smooth interfacial electron transfer from TiO2 to SnO2-NR through the high-quality junction and subsequent efficient charge separation due to the lattice strain-induced unidirectional potential gradient of the conduction band minimum in the SnO2-NR.