Formation of a photocatalytic WO3 surface layer on electrodeposited Al–W alloy coatings by selective dissolution and heat treatment

Abstract

In this study, we explored the feasibility of WO3 surface layer formation on electrodeposited Al–W alloy coatings by selective dissolution and heat treatment, with the aim of providing corrosion-resistant Al–W alloy coatings with photocatalytic self-cleaning properties under visible light illumination. The selective dissolution of Al and oxidation of residual W was carried out by immersing Al–W alloy films in an aqueous solution of nitric acid. A nanostructured H2WO4·H2O surface layer was formed on the alloy film by this process. The H2WO4·H2O layer was dehydrated to WO3 by heat treatment, yielding a multilayered WO3/Al–W alloy film with an approximately 300 nm thick WO3 layer. The WO3/Al–W alloy film exhibited photocatalytic self-cleaning, as demonstrated by the photodegradation of stearic acid and methylene blue. We also confirmed that selective dissolution and heat treatment did not significantly diminish the corrosion resistance of the Al–W alloy films.

Ultrafast Microwave Synthesis of WO3 Nanostructured Films for Solar Photocatalysis

“…[16,25] However, other WO 3 crystalline phases have been investigated as photocatalysts, including the WO 3 hexagonal, which has been reported as an excellent photocatalyst for dye degradation under visible light, [26] and the WO 3 orthorhombic, for which the interest in its photocatalytic activity has grown lately, especially for water purification. [27,28] DOI: 10.1002/pssr.202100196 Tungsten oxide (WO 3 ) 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 WO 3 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.…”

“…[ 16,25 ] However, other WO 3 crystalline phases have been investigated as photocatalysts, including the WO 3 hexagonal, which has been reported as an excellent photocatalyst for dye degradation under visible light, [ 26 ] and the WO 3 orthorhombic, for which the interest in its photocatalytic activity has grown lately, especially for water purification. [ 27,28 ]…”

Supported-Metal Oxide Nanoparticles-Potential Photocatalysts

“…For example, Higashino et al have fabricated a layer of WO 3 on the Al-W allow coatings by selective solution and heat treatment (Figure 10). The formed thin film WO 3 exhibits photocatalytic self-cleaning properties under the visible light irradiation [103].…”

“…Figure 10.SEM images of the surface and cross-sectional of WO 3 . Reproduced by Higashino et al[103].…”