Synthesis, Structural Correlations, and Photocatalytic Properties of TiO2 Nanotube/SnO2-Pd Nanoparticle Heterostructures

In this study, TiO2/SnO2-Pd heterostructures with enhanced photocatalytic activity were synthesized by the sensitization and activation of TiO2 nanotubes with SnO2-Pd nanoparticles. The growth of the SnO2-Pd nanopartides was dominated by the crystal structures of the TiO2 nanotubes and the sensitization time. On 450 degrees C annealed anatase TiO2 nanotubes, grown SnO2-Pd nanoparticles were uniformly stacked in a layer with specific structural orientations of Pd(111)parallel to anatase TiO2(200) and SnO2(110)parallel to anatase, TiO2(101). In contrast, on as-anodized amorphous TiO2 nanotubes, SnO2-Pd nanoparticles were randomly packed. The deposited rutile SnO2 nanoparticles induced the crystallization of amorphous TiO2 into a ruble phase with specific lattice correlations of Pd(111)parallel to rutile TiO2(101) and SnO2(110)parallel to rutile TiO2(110) during late-stage annealing at 450 degrees C. The rutile TiO2 parallel to SnO2-Pd heterostructures had a lower photocatalytic efficiency in the degradation of methylene blue than did the anatase heterostructures but had a higher efficiency than the bare TiO2 nanotubes.