Two-dimensional Bi2WxMo1−xO6 solid solution nanosheets for enhanced photocatalytic toluene oxidation to benzaldehyde

Abstract

Two-dimensional (2D) Bi2WO6, Bi2MoO6, and Bi2WxMo1−xO6 (x = 0.1, 0.3, 0.5, 0.7, and 0.9) solid solution photocatalysts were synthesized using the hexadecyl trimethyl ammonium bromide-assisted hydrothermal method. All of the samples displayed a morphology of irregularly rectangular nanosheets with a thickness of 7.0–17.4 nm. The photocatalytic performance of Bi2WxMo1−xO6 was much better than that of Bi2MoO6 or Bi2WO6 for the selective oxidation of toluene, with the Bi2W0.3Mo0.7O6 solid solution showing the highest benzaldehyde formation rate (1663 μmol/(g h)), which was about 1.95 and 2.83 times higher than those obtained over Bi2MoO6 and Bi2WO6, respectively. Furthermore, 91% benzaldehyde selectivity and excellent stability were also achieved over Bi2W0.3Mo0.7O6. The enhancement in photocatalytic activity of Bi2W0.3Mo0.7O6 was attributable to the balance of fast charge kinetics and optimized energy band structure. The results of the reactive species trapping and active radicals detection experiments reveal that the photogenerated holes, superoxide species, and carbon-centered radicals might play the important roles in the generation of benzaldehyde, and the possible photocatalytic toluene oxidation mechanisms over Bi2W0.3Mo0.7O6 were accordingly proposed.