Defect-Induced Cu-Doped TiO₂ Nanofibers for Enhanced Solar Hydrogen Generation

The electrospinning strategy is a versatile technique for synthesizing 1D TiO₂ nanofibers with high surface area and porosity. However, the large bandgap and rapid recombination of photogenerated carriers in TiO₂ have marred its practical applications. In this report, the precise control of diameter and morphology in TiO₂ nanofibers and Cu-doped 1D TiO₂ (Cu_x@TiO₂) nanofibers for photocatalytic hydrogen evolution reaction (HER) under visible light is investigated. The fibrous nanostructures facilitate better mass transport and access to active sites showing a pronounced rate in photocatalytic hydrogen evolution, 2.41 mmolg⁻¹h⁻¹, which is 120 times greater than that of pure TiO₂. The induced oxygen vacancies and defects, as revealed by XPS and Positron Annihilation Lifetime Spectroscopy (PALS), along with the characteristic EPR signal of Cu²⁺ (g_∥ = 2.33, g_⊥ = 2.06), support the effectiveness of photoinduced charge transfer and enhanced activity. The materials demonstrate superior electron transfer processes in HER, as evidenced by photocurrent responses. The synergistic interaction between Cu and TiO₂ significantly enhances visible light absorption while effectively suppressing the recombination of photogenerated charge carriers. Computations of the electron localization function (ELF) reveal that the lower adsorption energy on the Cu-doped TiO₂ [101] surface enhances water adsorption, thereby improving photocatalytic activity compared to pristine TiO₂.