Photocatalytic reduction of carbon dioxide using iodine-doped titanium dioxide with high exposed {001} facets under visible light

Abstract

Iodine-doped titanium dioxide nanosheets with high exposed {001} facets (IFTO) were synthesized by a two-step hydrothermal treatment followed by calcination at 350 °C. The photocatalyst samples were characterized by X-ray diffractometry, transmission electron microscopy, field emission scanning electron microscopy, ultraviolet-visible diffuse reflectance spectra, Brunauer–Emmett–Teller measurements and X-ray photoelectron spectroscopy. The IFTO were more active than surface-fluorinated TiO₂ nanosheets or iodine-doped TiO₂ nanoparticles in the gaseous reduction of CO₂ with water vapor. The IFTO photocatalytic activity was repeatable over five successive cycles. Coexisting I–O–Ti and I–O–I structures in the IFTO TiO₂ lattice contributed to visible light absorption and a high percentage of exposed {001} facets that enhance H₂O oxidation. Surface fluorination promoted the formation of unsaturated Ti atoms, which helped reduce CO₂ to CO₂⁻ and retard the recombination of photogenerated electron–hole pairs.