Enhanced photocatalytic activity of titanium dioxide in nitrogen fixation by the photon localization effect of SiO2 opal photonic crystals

Abstract

Photocatalytic conversion of nitrogen to ammonia with water under ambient conditions is a desired strategy. In the present work, in order to increase the activity of the TiO₂ photocatalyst for N₂ fixation, bilayer TiO₂/SiO₂ opal composite membranes were prepared via coupling TiO₂ films with SiO₂ opal photonic crystal (PC) films, and their photocatalytic performance in nitrogen fixation was tested. It was shown that when the photonic band gap (PBG) of the SiO₂ PCs matched with the UV-Vis absorption edge of TiO₂, the photon localization effect of SiO₂ PCs was maximized to promote the photon capture of TiO₂, resulting in more photogenerated electron–hole pairs for N₂ activation. The photon localization effect of SiO₂ PCs is negatively correlated with the thickness of the TiO₂ films in composite membranes. The nitrogen fixation activity of the TiO₂/SiO₂ opal composite membrane, with the thickness of TiO₂ film being 700 nm, was found to be 42.6 μmol g_cat⁻¹ h⁻¹, which was 68% higher than that of the plain TiO₂ film.