Mo-doped WO₃ nanowires for adsorbing methylene blue dye from wastewater

Doping tungsten oxide with other metals is a promising approach for obtaining improved properties as compared with its undoped counterpart. Here, the effect of molybdenum doping on the morphology, crystalline structure, and adsorption properties of nanostructured WO₃ was investigated. Undoped and Mo-doped hexagonal WO₃ (h-WO₃) nanowire bundles were synthesized by hydrothermal method. The samples were characterized by X-ray powder diffraction, transmission electron microscopy, scanning transmission electron microscopy, selected-area electron diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy. The surface areas of the samples were evaluated by N₂ adsorption–desorption isotherm, and their adsorption properties were evaluated based on their ability to adsorb cationic dye methylene blue (MB) in aqueous solution. Upon the addition of molybdenum, the morphology of the h-WO₃ nanowire changes from large bundles to narrow bundles with a higher number of isolated thin nanowires. Mo doping also has changed the crystalline structure, porosity, and surface area of the bundled h-WO₃ nanowires. Interestingly, Mo-doped h-WO₃ nanowire bundles exhibit an enhanced and faster MB uptake, thus implying that Mo-doping WO₃ can be an effective strategy to improve the adsorption properties, thereby adding value in developing alternative adsorption-based methods for wastewater treatment.