Enhanced Visible Light Active WO3 Thin Films Toward Air Purification: Effect of the Synthesis Conditions

Abstract

Taking our current environmental situation in the world into consideration, people should face growing problems of air and water pollution. Heterogeneous photocatalysis is a highly promising tool to improve both air and water quality through decomposition/mineralization of contaminants directly into harmless CO2 and H2O under ambient conditions. In this contribution, we focused on the synthesis of self-assembly WO3 thin films via an electrochemical approach in the aqueous electrolyte containing fluoride ions toward air purification. The effect of preparation conditions such as applied potential (10–50 V), anodization time (15–120 min), concentration of H2SO4 (0.5–1.5 M) and NaF (0.1–1.0 wt.%) on the morphology, photocurrent response, and photocatalytic activity addressed to removal of air pollutant in the presence of as-prepared WO3 samples were thoroughly examined and presented. The results revealed the growth of nanoplatelets and their gradual transformation into flower-like structures. The oxide layers and platelet thickness of the WO3 samples were found to be proportionally related with the synthesis conditions. The photocatalytic ability toward air purification was evaluated by degradation of toluene from air mixture using low-powered LEDs as an irradiation source (λmax = 415 nm). The highest photoactivity was achieved in presence of the sample which possessed a well-ordered, regular shape and repeatable distribution of flower buds (100% of degradation). The results have confirmed that the oxide layer thickness of the anodic WO3 significantly affected the photocatalytic activity, which increased with the increasing thickness of WO3 (to 1.05 μm) and then had a downward trend. The photocurrent response evidenced that the well-organized sample had the highest ability in photocurrent generation under UV-Vis and Vis irradiation. Finally, a possible growth mechanism of WO3 NFs was also discussed.

The Plasma Electrolytic Oxidation of Aluminum Using Microsecond-Range DC Pulsing

“…The recorded PL spectra for all PEO-processed Al samples under investigation in this study are shown in Figure 10. The PL spectra feature a pronounced spectral maximum at 500 nm, most probably originating from WO 3 [27,28]. The PL intensity follows the same order as the photocatalytic activity, which was also correlated with the W content observed from the EDS results.…”

Photoelectrochemical properties of plasma-induced nanostructured tungsten oxide

“…In this study, the photocatalytic activity was the highest when the oxide layer thickness was about 2 µm. Appropriate oxide layer thickness is beneficial to the movement of photogenerated electron-hole pairs and improves photocatalytic activity, as has been discussed [46]. Also, it has been discussed that the fabrication of unique structures with specific exposed crystal facets provides an excellent platform for WO 3 PEC performance tuning [11].…”

One-Step Dry Coating of Hybrid ZnO–WO3 Nanosheet Photoanodes for Photoelectrochemical Water Splitting with Composition-Dependent Performance

“…The most intense UV emission band of the WO3 NSs was observed at a lower wavelength of 362 nm than that of the ZnO NSs (378 nm). However, other emission bands were observed in the visible spectral range, covering violet (411 nm), blue (453 and 487 nm), and green (523 nm) emission bands [62]. The emission bands observed in the blue-green spectral region (453 and 487 nm) lie in the same energy range as the WO3 bandgap (~2.8 eV).…”