Enhanced photocatalytic oxidation of NO over g-C₃N₄-TiO₂ under UV and visible light

Highlights

• g-C₃N₄-TiO₂ was prepared by a facile calcination route utilizing commercial P25 and melamine.

• The activity of M400 was enhanced under Vis and UV light for the NO_x removal.

• The interaction of g-C₃N₄ and P25 is important for the activity.

• O₂⁻ is the main active species for NO oxidation to NO₃⁻ under Vis and UV light.

Abstract

In this work, graphitic carbon nitride-titanium dioxide (g-C₃N₄-TiO₂) was successfully prepared by a facile calcination route utilizing commercial P25 and melamine as the precursors. The as-prepared g-C₃N₄/TiO₂ photocatalysts were characterized systematically to elucidate their morphological structure and physico-chemical properties. The photocatalytic performance of g-C₃N₄-TiO₂ composites was investigated for the removal of NO_x in air. At the optimal g-C₃N₄ content (∼15 wt%, labeled as M400), the conversion of NO_x was 27%, which is higher than that of pure P25 (17%) and g-C₃N₄ (7%) under visible light. The activity of M400 was also enhanced under UV light. However, a mechanically mixed g-C₃N₄ and TiO₂ sample (with the content of g-C₃N₄ the same as M400, labeled as M0 + g-C₃N₄) did not improve the conversion of NO_x. Therefore, the interaction of g-C₃N₄ and P25 is important for the activity. EPR results indicated that O₂⁻ is the main active species for NO oxidation to NO₃⁻ under visible and UV light, which is responsible for the difference in activity between M400 and M0 + g-C₃N₄. The present study can improve our understanding of NO removal on the photocatalyst surface and the mechanism for the activity enhancement by the formation of g-C₃N₄-TiO₂.