Nano-layered K4Nb6O17 as an efficient photocatalyst for methyl orange degradation: Influence of solution pH and surface-dispersed gold nanoparticles

Abstract

The photocatalytic behavior of catalysts is closely related to their surface properties. Here, the K4Nb6O17 nanolayered photocatalyst was synthesized by the hydrothermal method and was subsequently surface-modified by being loaded with ultrafine gold nanoparticles via the decomposition of a gold cationic complex precursor [Au(en)2]3+ (en=ethylenediamine). The photocatalytic activities of the as-synthesized samples were evaluated in the photodegradation of the azo-dye methyl orange (MO) under UV irradiation. The photocatalytic activity of the pristine nanocrystalline K4Nb6O17 sample was efficiently improved as the initial solution pH was decreased; however, the photocatalytic activity was diminished when the concentration of dissolved oxygen was decreased. This behavior indicates that a synergistic effect of the dissolved oxygen molecules and surface bridging hydroxyl groups plays a key role in the photocatalysis. In addition, we found that an appropriate surface modification of the K4Nb6O17 by Au nanoparticles can significantly enhance its photocatalytic activity, an effect which may be attributed to the efficient separation of photogenerated charge carriers in this nanocomposite system.