Highly Efficient Photocatalytic Degradation of Hydrogen Sulfide in the Gas Phase Using Anatase/TiO₂(B) Nanotubes

Hydrogen sulfide (H₂S) is a highly toxic and corrosive gas that causes a foul odor even at very low concentrations [several parts per billion (ppb)]. However, industrially discharged H₂S has a concentration range of several tens of ppb to several parts per million (ppm), which conventional methods are unable to process. Therefore, advanced and sustainable methods for treating very low concentrations of H₂S are urgently needed. TiO₂-based photocatalysts are eco-friendly and have the ability to treat environmental pollutants, such as low-concentration gases, using light energy. However, there are no reports on H₂S decomposition or oxidation at concentrations below several ppb. Therefore, in this study, we employed anatase/TiO₂(B) nanotubes, which have a high specific surface area and an efficient charge-transfer interface, to treat H₂S. We successfully reduced 10 ppm of H₂S to 1 ppb or less at a kinetic rate of 75 μmol h^-1 g^-1. The suitability of our method was further demonstrated by the generation of sulfate ions and sulfur (as detected by X-ray photoelectron spectroscopy and ion chromatography), which are industrially useful as oxidation products, whereas sulfur dioxide, a harmful substance, was not produced. This is the first study to report H₂S decomposition down to the ppb level, providing meaningful solutions for malodor problems and potential health hazards associated with H₂S.