Fabrication of SnO₂-TiO₂ core-shell nanopillar-array films for enhanced photocatalytic activity

Highlights: • SnO₂-TiO₂ core-shell nanopillar-arrays on ITO glass were successfully fabricated. • The 3D heterojunction solves the problem of low photocatalytic activity of TiO₂ films. • SnO₂ is more suitable than ITO for the core layer to separate electron-hole pairs. - Abstract: Immobilized or deposited thin film TiO₂ photocatalysts are suffering from a low photocatalytic activity due to either a low photon absorption efficiency or a high carrier recombination rate. Here we demonstrate that the photocatalytic activity of TiO₂ can be effectively improved by the SnO₂-TiO₂ core-shell nanopillar-array structure which combines the benefits of SnO₂/TiO₂ heterojunction and high reaction surface area. The SnO₂-TiO₂ core-shell nanopillar-array films were fabricated using atomic layer deposition and dry etching techniques via barrier-free porous anodic alumina templates. The photocatalytic activity of the prepared films was evaluated by methylene blue (MB) bleaching under 352 nm UV light irradiation. The results show that the photocatalytic activity of TiO₂ film was 45% improved by introducing a SnO₂ film between TiO₂ and ITO glass substrate and was 300% improved by using the SnO₂-TiO₂ core-shell nanopillar-array structure. The 45% improvement by the SnO₂ interlayer is attributed to the SnO₂/TiO₂ heterojunction which separates the photogenerated electron-hole pairs in TiO₂ for MB degradation, and the high photocatalytic activity of the SnO₂-TiO₂ core-shell nanopillar-array films is attributed to the three dimensional SnO₂/TiO₂ heterojunction which owns both the carrier separation ability and the high photocatalytic reaction surface area.