Ultrafast Microwave Synthesis of WO₃ Nanostructured Films for Solar Photocatalysis

Tungsten oxide (WO₃) nanostructured films are synthesized under microwave radiation with synthesis times of 5 and 10 min, at 150 or 180 °C. This ultrafast synthesis route results in uniform and well-crystallized WO₃ nanostructured films fully covering the substrates. A plate-like hierarchical structure is observed at 150 °C, and closely packed rectangular nanorods are formed at 180 °C. For both temperatures, the nanostructures self-organize into larger flower-like structures. The increase of the synthesis time from 5 to 10 min at 180 °C results in thicker films, reaching ≈4 μm. X-ray diffraction (XRD) and Raman spectroscopy reveal that the films grow with the WO₃ orthorhombic crystalline phase (o-WO₃·0.33H₂O). Photoluminescence (PL) measurements are performed for all the films, and their optical bandgaps are estimated through diffuse reflectance spectroscopy. The WO₃ films have their photocatalytic activity assessed from rhodamine B (RhB) degradation under solar radiation. The Mott–Schottky plots confirm the n-type character of the films with the flat-band potentials and electron concentrations being estimated for the best photocatalysts. This study associates the eco-friendly, fast, and low-cost aspects of the synthesis route to the production of highly photoactive materials, which can effectively contribute to environmental remediation.