Influence of interface defects and Zr doping on the photocatalytic activity of TiO2 nanofibers in water splitting
Mehrdad Mehdikhanloo, Zahra Hagheh Kavousi, Massomeh Ghorbanloo, Amr A. Nada, Heba H. El-Maghrabi, Rasha Hosny, Fouad Zahran, Roman Viter, Djamel Bezzerga, Jisang Hong, Bernard Fraisse, Fathi S. Soliman, Igor Iatsunskyi, Emerson Coy, Yaovi Holade, Mitra Saffari, Mikhaël Bechelany
Abstract
Efficient hydrogen production by water photocatalysis requires effective charge separation and optimal reactant-catalyst interactions. However, producing catalysts with these features is still challenging. Here, electrospinning and calcination were used to fabricate zirconium (Zr)-doped TiO 2 nanofibers with controlled crystalline phase. In all tested nanofiber samples (pure TiO 2 and after doping with different Zr amounts), TiO 2 was detected mainly in the anatase form. All nanofibers displayed high purity and crystallinity. Moreover, X-ray photoemission spectroscopy showed that Zr was present as Zr 4 + ions on the TiO 2 surface. The Zr-doped TiO 2 nanofiber band gaps (determined with the Kubelka–Munk function) ranged from 3.00 eV to 3.2 eV ( vs 3.09 for TiO 2 ). The absorption of visible light was improved in Zr-doped TiO 2 nanofibers because Zr addition led to the creation of intermediate electronic levels between the conduction and valence bands, and to the decrease of the electron recombination rate. Then, Zr doping effect on TiO 2 electronic structure and photocatalytic properties was evaluated by density functional theory modeling. The nanofibers with 4 mol% of ZrOCl 2 ·8 H 2 O exhibited the highest photocatalytic activity under visible light (hydrogen evolution rate of 2500 μmol·g⁻¹·h⁻¹, 23 times higher compared with pure TiO 2 nanofibers). These one-dimensional nanostructures also showed excellent recyclability and sustained high photocatalytic efficiency, promising features for environmental and energy applications. The one-dimensional ZrO 2 /TiO 2 heteroarchitectures demonstrate remarkable visible-light photocatalytic activity for water splitting. In fact, their performance is significantly enhanced, exhibiting a photocatalytic activity that is more than 23 times higher than pristine TiO 2 nanofibers. This enhancement can be attributed to the interface defect and Zr doping of TiO 2 , which plays a crucial role in improving the separation of photogenerated electrons and holes. • Zr-TiO₂ nanofibers were made via electrospinning, achieving high purity and controlled crystallinity. • XPS: Zr⁴⁺ ions modified TiO₂, tuning the band gap (3.00–3.2 eV) and enhancing light absorption. • Zr doping created intermediate electronic levels, reducing electron recombination and improving photocatalytic efficiency. • DFT: Zr-TiO₂ modeling showed improved charge separation and enhanced electronic structure. • 4 mol% Zr-doped nanofibers exhibited a 23× higher hydrogen evolution rate than pure TiO₂, with excellent recyclability.