CTAB-assisted hydrothermal synthesis of silver vanadates and their photocatalytic characterization

Silver vanadates, visible-light-driven photocatalysts, have been synthesized using hydrothermal treatment with the assistance of cetyltrimethylammonium bromide (CTAB). It is found that CTAB during the hydrothermal synthesis significantly affects the morphology, crystal structure, optical absorbance, and photocatalytic properties of silver vanadates. The pure silver vanadate oxides (SVO) consisted of mixed structures of Ag4V2O7 and αα-Ag3VO4, with αα-Ag3VO4 as the major phase. As the amount of CTAB increased, the crystal phase of CTAB-SVO sample approached Ag4V2O7. The band gaps for all CTAB-SVO samples were found to be in the range of 2.29–2.43 eV. The reactivity of 0.5%CTAB-SVO (surface area, 6.51 m2 g−1) on isopropanol was 10 times higher than that of P25 (surface area, 49.04 m2 g−1) under visible light irradiation. The photocatalytic activity of CTAB-SVO sample decreased with an increase of Ag4V2O7. The highest photocatalytic activity of 0.5%CTAB-SVO had the highest intensities of surface hydroxyl groups, which were detected using the in-situ DRIFT technique. The density of surface hydroxyl groups, not the crystalline structure, was confirmed as the key factor influencing the photocatalytic activity.