Insights into the impact of self-contained sulfur impurity on the superior photocatalytic activity of UV100

Abstract

The commercial Hombikat UV100 is a TiO2 photocatalyst that is less studied and used than Aeroxide P25, resulting in limited knowledge associated to it. In this study, we used ICP-OES, XPS, and TGA analyses to show that UV100 contains non-negligible traces of sulfur as-received, which can be migrated to the surface of TiO2 through a simple calcination treatment. Ionic chromatography, DRIFTS, and pyridine-TPD analyses confirmed that a portion of the surface sulfate after the thermal induced migration can be removed by distilled water, along with associated sodium cations, without impacting the surface chemistry of the photocatalyst. Calcination of UV100 enhanced the photocatalytic activity in the liquid-phase degradation of phenol, paracetamol, and chloramphenicol, and this activity remained relatively unaffected by the leaching of sulfate. Although EPR indicated that surface-bound sulfate might act as electron trapping centers or oxygen chemisorption centers, the primary reason for the improved photocatalytic activity is likely the increased crystallinity of the anatase phase due to high-temperature calcination, aided by sulfur’s retarding effect on the anatase-to-rutile transition.