Band bending and valence band shifting of sub-monolayer TiO₂ functionalized SnO₂ nanowires

Sub-monolayer TiO₂ over-layers were deposited on SnO₂ nanowires (NWs) by atomic layer deposition. X-ray photoelectron spectroscopy, Mott–Schottky plots and photoluminance spectra were used to investigate the band structure and the separation of electron–hole pairs at the SnO₂/TiO₂ interface. The results showed that the valence band maximum of SnO₂ NWs shifted to lower binding energies after functionalization, and significant upward band edge bending at the interface was confirmed. The rearrangement of energy band accelerated the separation of photo-generated electron–hole pairs leading to the improvement of photocatalytic degradation rate of methyl orange (MO, C₁₄H₁₄N₃NaO₃S) under UV irradiation.