Highly porous N-doped TiO2 hollow fibers with internal three-dimensional interconnected nanotubes for photocatalytic hydrogen production

Abstract

Fabrication of TiO₂ hollow fibers was conducted by atomic layer deposition (ALD) with polysulfone fibers (PSFs) as a template. After the ALD process, the PSFs were removed by heat treatment at 500 °C for 1 h to form anatase TiO₂ hollow fibers. They were then doped with nitrogen up to ∼5 at% by treatment in NH₃ at 500–600 °C. The N-doped TiO₂ hollow fibers remained porous and the wall was full of three-dimensional interconnected nanotubes. The X-ray photoelectron spectroscopic analysis indicated that nitrogen was substitutionally doped into oxygen sites of the TiO₂ lattice, resulting in band gap narrowing and more absorption in the visible light region. They exhibited significantly improved photocatalytic activity for water splitting due to a lower energy gap, higher reactive surface area (∼100 m² g⁻¹), multiple light reflection, and better charge separation efficiency. The fibers treated at 600 °C for 1 h, containing ∼2.5 at% nitrogen, generated 0.185 μmol g⁻¹ of hydrogen after 6 h of irradiation with a 150 W Xe lamp.