Surface Wetting Behavior of a WO₃ Electrode under Light-Irradiated or Potential-Controlled Conditions

Abstract

Surface wettability conversion of WO3 was investigated through electrochemical or photochemical reaction on a polycrystalline WO3 electrode. The initial water contact angle for the WO3 electrode was about 15°, and it was slightly reduced to 9° by cathodic polarization in water under darkness. In contrast, when the WO3 electrode was irradiated with visible light during anodic polarization, the water contact angles were drastically decreased to below 3°. The wettability conversions under aerobic or humid atmospheres were also evaluated, and the presence of oxygen and water molecules was important for the hydrophilic conversion of WO3. On the basis of these results, we discuss a possible mechanism for the surface wettability conversion of WO3. We found that photogenerated holes are indispensable in achieving superhydrophilic conversion on the surface of WO3, whereas the reduction in WO3 by electrons could only generate a slight hydrophilic change.

Complete oxidation of acetaldehyde over a composite photocatalyst of graphitic carbon nitride and tungsten(VI) oxide under visible-light irradiation

“…CNWx and HTWx samples showed no linear relationship between relative reflectance at the wavelength of 800 nm and WO3 content. Since photoabsorption at a longer wavelength of 500 nm is attributed to the W 5+ state in WO3, which is generated by electron accumulation in WO3 and reduction treatment of WO3 [29][30][31], a nonlinear relationship means that electron accumulation in WO3 was decreased by composition with g-C3N4. A similar phenomenon was observed in the Z-scheme composite photocatalyst of WO3 and CaFe2O4 [13].…”

A Nanosegregant Approach to Superwettable and Water‐Attracting Surfaces

“…Although there are quite a number of superhydrophilic materials reported in the literature, [19][20][21][22][23][24][25][26] to the best of our knowledge, the nanosegregant in Figure 3 is the first one exhibiting of the water-attracting function. Due to their superwettability, the nanosegregants also show anti-fogging effect as illustrated in Figure 3e.…”

“…Compared to existing routes [19][20][21][22][23][24][25][26] to superwettability, our method is simple, cost-effective and easily scalable for mass production. PEDT:PSSH is a very common polymer blend which is commercially available in large quantities (kilograms).…”

“…In the literature, superhydrophilicity is mainly achieved by the UV-irradiation of oxide semiconductor films such as TiO 2 (titanium oxide), [19][20][21] ZnO (zinc oxide), [22] and WO 3 . [23] In this case, the superhydrophilicity is induced by photon-generated short-lived charges, which will gradually disappear without UV illumination. There are also other efforts involving the chemical modifications of nanostructures (e.g., carbon nanotubes) for the water wettability of surfaces.…”

“…Compared to the technological success in superhydrophobicity,1–6, 11–18 methods to obtain superhydrophilicity are very limited. In the literature, superhydrophilicity is mainly achieved by the UV‐irradiation of oxide semiconductor films such as TiO 2 (titanium oxide),19–21 ZnO (zinc oxide),22 and WO 3 23. In this case, the superhydrophilicity is induced by photon‐generated short‐lived charges, which will gradually disappear without UV illumination.…”