A Hybrid Amorphous/Crystalline TiO₂ Material with Enhanced Photocatalytic Performance

Abstract Whereas crystalline TiO₂ is widely used as a photocatalyst for solar energy conversion, the use of amorphous TiO₂ is limited by diminished performance. Herein, the highly active photocatalyst composed of low‐crystalline TiO₂ prepared by simple heat treatment of amorphous material is reported. Transmission electron microscopy, X‐ray diffraction, Raman, X‐ray absorption spectroscopy, and scanning transmission electron microscopy show that the low crystalline catalyst is hetero‐phase amorphous/anatase (m_amorphous: m_anatase ≈ 2:3). Enhanced photocatalytic performance derives from the difference in conduction band potential between the phases, which promotes charge transfer and photochemical conversion. The photocatalyst calcined at 300 °C (T‐300) exhibits superior performance over commercial P25 (Degussa) for elimination of perrhenate, Re(VII), a surrogate for Tc(VII), and furthermore remains stable after several recycles. The high efficiency of Re(VII) removal by T‐300 is likely to correlate with active radicals ∙CO₂⁻ in the TiO₂/HCOOH system. In addition to identifying a simple and effective photocatalyst, the results more generally elucidate titania‐based photocatalysis.