In the current work, TiO 2 /Al 2 O 3 binary oxide photocatalysts were synthesized via two different sol-gel protocols (P1 and P2), where various TiO 2 to Al 2 O 3 mole ratios (0.5 and 1.0) and calcination temperatures (150-1000 • C) were utilized in the synthesis. Structural characterization of the synthesized binary oxide photocatalysts was also performed via BET surface area analysis, X-ray diffraction (XRD) and Raman spectroscopy. The photocatalytic NO(g) oxidation performances of these binary oxides were measured under UVA irradiation in a comparative fashion to that of a Degussa P25 industrial benchmark. TiO 2 /Al 2 O 3 binary oxide photocatalysts demonstrate a novel approach which is essentially a fusion of NSR (NO x storage reduction) and PCO (photocatalytic oxidation) technologies. In this approach, rather than attempting to perform complete NO x reduction, NO(g) is oxidized on a photocatalyst surface and stored in the solid state. Current results suggest that alumina domains can be utilized as active NO x capturing sites that can significantly eliminate the release of toxic NO 2 (g) into the atmosphere. Using either (P1) or (P2) protocols, structurally different binary oxide systems can be synthesized enabling much superior photocatalytic total NO x removal (i.e. up to 176% higher) than Degussa P25. Furthermore, such binary oxides can also simultaneously decrease the toxic NO 2 (g) emission to the atmosphere by 75% with respect to that of Degussa P25. There is a complex interplay between calcination temperature, crystal structure, composition and specific surface area, which dictate the ultimate photocatalytic activity in a coordinative manner. Two structurally different photocatalysts prepared via different preparation protocols reveal comparably high photocatalytic activities implying that the active sites responsible for the photocatalytic NO(g) oxidation and storage have a non-trivial nature.

a b s t r a c tTiO 2 -Al 2 O 3 binary oxide surfaces were utilized in order to develop an alternative photocatalytic NO x abatement approach, where TiO 2 sites were used for ambient photocatalytic oxidation of NO with O 2 and alumina sites were exploited for NO x storage. Chemical, crystallographic and electronic structure of the TiO 2 -Al 2 O 3 binary oxide surfaces were characterized (via BET surface area measurements, XRD, Raman spectroscopy and DR-UV-Vis Spectroscopy) as a function of the TiO 2 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 NO 2 (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.

a b s t r a c tPolystyrene cross-linked divinyl benzene (PS-co-DVB) microspheres were used as an organic template in order to synthesize photocatalytic TiO 2 microspheres and microbowls. Photocatalytic activity of the microbowl surfaces were demonstrated both in the gas phase via photocatalytic NO(g) oxidation by O 2 (g) as well as in the liquid phase via Rhodamine B degradation. Thermal degradation mechanism of the polymer template and its direct influence on the TiO 2 crystal structure, surface morphology, composition, specific surface area and the gas/liquid phase photocatalytic activity data were discussed in detail. With increasing calcination temperatures, spherical polymer template first undergoes a glass transition, covering the TiO 2 film, followed by the complete decomposition of the organic template to yield TiO 2 exposed microbowl structures. TiO 2 microbowl systems calcined at 600 • C yielded the highest per-site basis photocatalytic activity. Crystallographic and electronic properties of the TiO 2 microsphere surfaces as well as their surface area play a crucial role in their ultimate photocatalytic activity. It was demonstrated that the polymer microsphere templated TiO 2 photocatalysts presented in the current work offer a promising and a versatile synthetic platform for photocatalytic DeNO x applications for air purification technologies.