Tolerance to electron beams of TiO2 film photocatalyst

Highlights: • The surface roughness of TiO₂ increased after electron beam (EB) irradiation. • Chemical properties and photocatalytic activity were unchanged on EB irradiation. • TiO₂ has sufficient resistance to an EB (480 keV, 2.4 MGy). -- Abstract: In orbit, contamination outgassed from spacecraft materials has been reported to degrade optical systems such as CCD cameras, lenses, mirrors, and optical filters mounted on a spacecraft. We focus on TiO₂ photocatalyst to solve this contamination problem. TiO₂ has the potential to decompose contaminants and suppress the deterioration of optical systems in orbit. However, the resistance of TiO₂ itself to electrically charged particles, i.e., electrons in space, has not been clarified. The TiO₂ films were irradiated with an electron beam (EB) with an energy of < 480 eV in a vacuum. The irradiation dose was about 2.4 MGy. Chemical properties, surface morphology, and photocatalytic activity were compared before and after EB irradiation. Almost basic properties except surface roughness were unchanged, and the change of surface roughness was very small. These results indicate that TiO₂ has sufficient resistance to an EB.