Abstract
Bismuth oxide, tin oxide and Pd metal (Pd/SnBi3SG) hybrids, synthesized via sol-gel technique while employing polyethylene glycol template at a ratio of 3 (Bi/Sn = 3) were tested toward the photocatalytic oxidation of fluorene under ultraviolet and visible light irradiations in comparison with Pd/Bi-SG and Pd free SnBi3SG photocatalysts. These catalysts were characterized using X-ray diffraction (XRD), UV-vis diffuse reflectance (DRUV-vis), N-2 sorptiometry, Raman spectroscopy, transmission electron microscopy (TEM) and GC-MS technique, which used for analyzing the photo-oxidation products. The actual photocatalyst exhibited the highest activity (100% conversion, TOF approximate to 9.4 x 10(-6) s(-1), fluorenone/fluorenol = 3/1) following oxygen flushing for 30 min (35 ml/min) before UV irradiation. This was mainly due to the close proximity between beta-Bi2O3 and Bi2Sn2O7 heterojunction as well as increasing the mesoporosity margin comparatively. On the other hand, the Pd/Bi-SG catalyst that exhibited smaller crystallite size (20 nm vs. 44 nm) and higher surface area (21.0 vs. 12.0 m(2)/g) than Pd/SnBi3SG indicated lower activity (Pd/Bi-SG, 72% cony.). This highlights the importance of the modified electronic structure of Pd/SnBi3SG in designing efficient charge separation as well as high quantum yield value (Phi similar to 0.1 +/- 0.05) exceeding that of Pd/Bi-SG (3 x 10(-2)) and SnBi3(SG) (10(-2)) photocatalysts. The catalytic behavior and mechanism, reactivity-structure relationship and recyclable use of the hybrid photocatalysts have been thoroughly examined. An indirect chemical probe method using active species scavengers elucidated that the photo-oxidation mechanism was proceeded via holes and O-2(-) moieties rather than singlet oxygen moieties. (C) 2014 Elsevier Inc. All rights reserved.