Deposition of ultrasmall γ-Mo2N nanocrystals on TiO2 nanowires and their promotion effect on photocatalytic activity

Mo 2 N decorated TiO 2 nanowires were obtained via impregnating titanate nanowires with a mixture of (NH 4 ) 6 Mo 7 O 24 and hexamethylenetetramine , followed by the calcination at 600–800 o C in N 2 atmosphere. The results show that only Mo 6+ species can be found in the sample calcined at 600 o C while Mo element is still dominantly in the form of Mo 6+ with a negligible amount of γ-Mo 2 N (namely Mo δ+ , 0 ​< ​δ ​< ​4) and Mo 4+ at 700 o C. In the sample calcined at 800 o C, however, ultrasmall γ-Mo 2 N nanocrystals with an average size of about 3.3 ​nm can be observed on the surface of TiO 2 nanowires. The photocatalytic activity test reveals that, although the γ-Mo 2 N-absent sample obtained at 800 o C is dominantly in the form of inert rutile TiO 2 , the introduction of γ-Mo 2 N nanocrystals can significantly improve its performance to be more than doubled in methyl orange (MO) removal percentage, increasing from 36.5% to 75.5% after 2h irradiation (high-pressure mercury lamp), due to the formation of heterojunction between γ-Mo 2 N and TiO 2 nanowires. Furthermore, 5% γ-Mo 2 N decorated TiO 2 exhibit better photocatalytic activity due to its higher surface area and more heterojunctions between γ-Mo 2 N and TiO 2 . This γ-Mo 2 N decorated TiO 2 photocatalyst can broaden the practical scope of rutile TiO 2 and have a promising potential in photocatalytic application.