The fabrication method of Pd-WO3 nanorods is achieved by hydrothermal method as below: 1 gram of cetyltrimethylammonium bromide was dissolved in 20 mL of absolute ethyl alcohol, 10 mL of ultrapure water and 0.5 mL of 0.05 M nitric acid, and the resulting mixture was subjected to magnetic stirring for 60 min. Then, a predetermined amount of ammonium paratungstate (APT) was added to the above mixture, and the resulting mixture was subjected to magnetic stirring for 30 min. Finally, the mixture was heated at 140 °C for 24 h in a Teflon-lined autoclave. The produced materials were washed multiple times with distilled water and ethanol and subsequently dried in air at 100 °C for 24 h. A photo-assisted deposition method was used to deposit different weight percentages of Pd metal (0.05, 0.10, 0.15 and 0.20 wt%) on the surface of the WO3 nanorods as follows. One gram of WO3 nanorods was dispersed in an aqueous solution of palladium chloride, and the resulting mixture was exposed to UV (150 W) light for 24 h. The resulting materials were then washed several times with distilled water and ethanol and then calcined at 120 °C for 3 h under hydrogen gas.

In summary, Ammonium paratungstate has used in Pd-doped WO3 nanorods for photocatalytic degradation of herbicides. The deposition of palladium onto the WO3 surface resulted in enhanced degradation of 2,4-D under visible light, indicating increased photocatalytic activity. The highest photocatalytic activity was measured for 0.15 wt% Pd-WO3 nanorods, which also possessed photocatalytic stability, as it could be used five times without a loss of structure and activity.