Photocatalytic degradation of hydrogen sulfide and in situ FT-IR analysis of reaction products on surface of TiO2

The photocatalytic oxidation of hydrogen sulfide at the gas/solid interface was investigated using TiO2 as the photocatalyst. A malodorous compound, hydrogen sulfide was removed via a photocatalytic process under ambient conditions. Hydrogen sulfide was oxidized to sulfate species on the surface of TiO2 without producing a noticeable gaseous intermediate, e.g., sulfur dioxide. The formation of sulfate species was confirmed by X-ray photoelectron spectroscopy (XPS). The surface chemistry of this photocatalytic oxidation was probed using two different types of in situ infrared (IR) spectroscopy techniques: diffuse reflectance IR spectroscopy (DRIFTS), and thin-film transmission IR spectroscopy. From the results obtained from DRIFT analysis, sulfate ions were accumulating proportionally with time on the surface of the catalyst during the course of the photocatalytic reaction. From further information gleaned from the transmission IR spectra (detected peaks at 1093 and 996 cm−1), SO2− may be one of the predominant intermediates that appear over the time of this reaction. Although these results do not reveal the entire reaction pathway of the conversion of sulfides to sulfates, our results using these in situ FT-IR techniques have been valuable in confirming that the photocatalytic oxidation of hydrogen sulfide occurs on the surface of particulate TiO2.