Enhancement of photocatalytic activity and stability of Ag2CO3 by formation of AgBr/Ag2CO3 heterojunction in mordenite zeolite

Abstract

Two serious problems for semiconductor photocatalysts are their poor photocatalytic activity and low stability. In this work, Ag2CO3 nanoparticles incorporated in mordenite zeolite (MOR) by a facile precipitation method. Silver bromide (AgBr) with different weight percentage (20%, 40% and 50%) was coupled into Ag2CO3-MOR composite and producing a series of novel AgBr/Ag2CO3-MOR nanocomposites. The effects of AgBr on the Ag2CO3–MOR catalyst for the photocatalytic degradation of methyl blue (MB) under visible light irradiation have been investigated. The structure, composition and optical properties of nanocomposites were investigated by UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM). The prepared AgBr/Ag2CO3-MOR photocatalyst with the optimal content of AgBr (50wt%) indicated higher photocatalytic activity than that of the Ag2CO3-MOR and Ag2CO3 for degradation of methylene blue (MB) under visible light irradiation. For studying of stability of nanocomposites, Fe+3 ions, as a cheap and available cocatalyst, was inserted into mordenite matrix (Fe3+/MOR) by impregnation method. The hybrid material (AgBr/Ag2CO3) was synthesized in the Fe3+/MOR matrix by precipitation method. The cycle experiments on the AgBr/Ag2CO3-Fe/MOR nanocomposite indicated that cocatalyst, not only to improve photocatalytic activity, but also enhance photoinduced stability of photosensitive silver compounds in all cycles with respect to MOR. On the basis of the experimental results, a possible mechanism for the enhanced photocatalytic activity and photoinduced stability of silver compounds by Fe3+ cocatalyst was proposed. The mordenite support played an important role in decreases of recombination of photogenerated electrons-holes and increases of MB absorption. The Fe cocatalyst reduced photocorrosion of silver compounds.