Hierarchical Top-Porous/Bottom-Tubular TiO₂ Nanostructures Decorated with Pd Nanoparticles for Efficient Photoelectrocatalytic Decomposition of Synergistic Pollutants

In this paper, top-porous and bottom-tubular TiO₂ nanotubes (TiO₂ NTs) loaded with palladium nanoparticles (Pd/TiO₂ NTs) were fabricated as an electrode for an enhanced photoelectrocatalytic (PEC) activity toward organic dye decomposition. TiO₂ NTs with a unique hierarchical top-porous and bottom-tubular structure were prepared by a facile two-step anodization method and Pd nanoparticles were decorated onto the TiO₂ NTs via a photoreduction process. The PEC activity of Pd/TiO₂ NTs was investigated by decomposition of methylene blue (MB) and Rhodamine B (RhB). Because of formation Schottky junctions between TiO₂ and Pd, which significantly promoted the electron transfer and reduced the recombination of photogenerated electrons and holes, the Pd/TiO₂ NT electrode showed significantly higher PEC activities than TiO₂ NTs. Interestingly, an obvious synergy between two dyes was observed and corresponding mechanism based on facilitated transfer of electrons and holes as a result of a suitable energy level alignment was suggested. The findings of this work provide a fundamental insight not only into the fabrication but also utility of Schottky junctions for enhanced environmental remediation processes.