A Photoresponsive Rutile TiO ₂ Heterojunction with Enhanced Electron–Hole Separation for High-Performance Hydrogen Evolution

Rutile titanium dioxide (TiO ₂ ) is a promising photocatalyst due to its high thermodynamic stability and few intragrain defects. However, it has not yet achieved photocatalytic activity comparable to that of anatase TiO ₂ owing to its higher recombination rate of electron–hole pairs. To effectively separate the electron–hole pairs in rutile TiO ₂ , a facet heterojunction (FH) structure to prolong the lifetime of the photogenerated electrons is proposed. Ultrathin TiO ₂ nanosheets with different facets are coated in situ onto TiO ₂ nanorod (NR) substrates, where FHs are built among the nanosheets as well as between the nanosheets and NR substrates. The as-prepared rutile TiO ₂ , with an FH structure (FH-TiO ₂ ), serves as an effective photocatalyst for water splitting. More than 45 and 18 times higher photogenerated current density and H ₂ production rate, respectively, are obtained compared to those of pure rutile TiO ₂ NRs. Moreover, FH-TiO ₂ delivers a 0.566 mmol g ⁻¹ h ⁻¹ H ₂ production rate even in pure water. This study offers important insights into the rational design of rutile TiO ₂ structures for highly efficient photocatalytic reactions.