TiO₂–Al₂O₃ binary mixed oxide surfaces for photocatalytic NO_x abatement

Highlights: • TiO₂/Al₂O₃ binary oxide photocatalysts were synthesized. • Photocatalysts characterized as a function of temperature and composition. • Photocatalytic NO_x abatement performances investigated. • A novel TiO₂/Al₂O₃ photocatalyst superior than P25 reported. - Abstract: TiO₂–Al₂O₃ binary oxide surfaces were utilized in order to develop an alternative photocatalytic NO_x abatement approach, where TiO₂ sites were used for ambient photocatalytic oxidation of NO with O₂ and alumina sites were exploited for NO_x storage. Chemical, crystallographic and electronic structure of the TiO₂–Al₂O₃ binary oxide surfaces were characterized (via BET surface area measurements, XRD, Raman spectroscopy and DR-UV-Vis Spectroscopy) as a function of the TiO₂ loading in the mixture as well as the calcination temperature used in the synthesis protocol. 0.5 Ti/Al-900 photocatalyst showed remarkable photocatalytic NO_x oxidation and storage performance, which was found to be much superior to that of a Degussa P25 industrial benchmark photocatalyst (i.e. 160% higher NO_x storage and 55% lower NO₂(g) release to the atmosphere). Our results indicate that the onset of the photocatalytic NO_x abatement activity is concomitant to the switch between amorphous to a crystalline phase with an electronic band gap within 3.05–3.10 eV; where the most active photocatalyst revealed predominantly rutile phase together and anatase as the minority phase