Improvement in photocatalytic activity of stable WO3 nanoplatelet globular clusters arranged in a tree-like fashion: Influence of rotation velocity during anodization

Abstract

Improvement in photocatalytic activity of stable WO3 nanoplatelet globular clusters arranged in a tree-like fashion: Influence of rotation velocity during anodization. Applied Catalysis B:

A simple method to fabricate high-performance nanostructured WO3 photocatalysts with adjusted morphology in the presence of complexing agents

“…All anodization tests were carried out for 4 h applying a cell potential of 20 V, at a temperature of 50 ºC and at a rotation velocity (using a rotating disk electrode, RDE) of 375 rpm. These values were chosen according to a previous work [6]. Anodization electrolytes consisted of solutions of complexing agents or ligands in several concentrations: fluoride anions (prepared from NaF in the range 0-0.25 M) and hydrogen peroxide (in the range 0-0.2 M).…”

“…Besides, WO3 can also absorb a part of the visible rays of the solar spectrum (its band-gap is Eg ≈ 2.6 eV, which corresponds approximately to a wavelength of ∼480 nm) [1][2][3][4]. Tungsten trioxide has been employed in technologically advanced fields, such as photoelectrochemistry and photodegradation of organic pollutants [4][5][6][7][8][9][10][11][12][13][14], dye-sensitized solar cells [15], gas sensors [16] or electrochromic devices [17][18][19].…”

“…WO3 nanostructures (nanopores, nanorods/nanowires, nanoplatelets, etc.) have been synthesized by a number of different techniques such as hydrothermal methods [3,12,21], solvothermal methods [22,23], sol-gel [24,25], deposition processes (laser deposition [17], electrodeposition [1,[26][27][28][29][30][31][32], chemical vapor deposition [33], atomic layer deposition [14], RF sputtering [34], spin coating [35]), dry chemistry methods (plasma-assisted approach [36]) and anodization [1,6,7,15,37]. It is known that the chemistry of aqueous tungsten solutions is complex, since a wide variety of species can be obtained depending on many factors, such as the composition, the pH or the temperature of the solutions [38].…”

“…The formation of condensed isopolytungstates in acidic solutions and, especially, the interaction of WO3 with ligands or complexing agents (such as fluoride, hydrogen peroxide or polycarboxylic acids) can be used to customize WO3 nanostructures, thus providing a wide range of possibilities to obtain new morphologies and improved properties. Although the chemistry of tungsten species is incompletely understood, there is increasing interest in tungsten (VI) complexation for the fabrication of WO3 nanostructures [1,6,8,9,23,[28][29][30][31][32][39][40][41][42][43][44][45].…”

“…However, little work concerning the synthesis of WO3 nanostructures by anodization in solutions containing complexing agents has been developed, and most of these studies deal with tungsten anodization in the presence of fluoride anions [6,8,9,39,40,45].…”