Surface Ba species effective for photoassisted NOx storage over Ba-modified TiO2 photocatalysts

• Ba-modified TiO2 photocatalysts showed high activity in photoassisted NOx storage.
• Modification of TiO2 photocatalysts with Ba enhanced the photocatalytic activity.
• Ba loading had an significant effect on the photocatalytic activity.
• Ba–Ti mixed oxides were formed on a TiO2 surface after O2 pretreatment at 773 K.
• The generated Ba–Ti mixed oxides function as an effective NOx storage material.

Surface modification of a TiO2 photocatalyst with Ba species was investigated in photoassisted nitrogen oxide (NOx) storage under UV-light irradiation. The NOx storage capacity in the Ba-modified TiO2 photocatalyst was 1.4 times higher than that of the non-modified TiO2 photocatalyst. Structure and role of the surface Ba species on a TiO2 surface were characterized using temperature programmed reaction (TPR), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). The characterization results suggested that Ba–Ti mixed oxides with a two-dimensional layer and amorphous structure on a TiO2 surface were generated via decomposition of Ba(NO3)2 precursors by O2 pretreatment at 773 K. Based on the results of the characterizations and the reactions, the generated Ba–Ti mixed oxides on a TiO2 surface stored NOx more densely than the TiO2 surface; therefore, the generation improved the activity in the photoassisted NOx storage under UV-light irradiation.

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