Hierarchical top-porous/bottom-tubular TiO ₂ nanostructures decorated with Pd nanoparticles for efficient photoelectrocatalytic decomposition of synergistic pollutants

In this paper, top-porous and bottom-tubular TiO ₂ nanotubes (TiO ₂ NTs) loaded with palladium nanoparticles (Pd/TiO ₂ NTs) were fabricated as an electrode for an enhanced photoelectrocatalytic (PEC) activity toward organic dye decomposition. TiO ₂ 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 TiO ₂ NTs via a photoreduction process. The PEC activity of Pd/TiO ₂ NTs was investigated by decomposition of methylene blue (MB) and Rhodamine B (RhB). Because of formation Schottky junctions between TiO ₂ and Pd, which significantly promoted the electron transfer and reduced the recombination of photogenerated electrons and holes, the Pd/TiO ₂ NT electrode showed significantly higher PEC activities than TiO ₂ 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.