Effects of acidity on the formation and adsorption activity of tungsten oxide nanostructures prepared via the acid precipitation method

Temperature-mediated Phase Transformation and Optical Properties of Tungsten Oxide Nanostructures Prepared by Facile Hydrothermal Method

“…In a highly acidic environment, tungstic acid interacts with water molecules and transforms into the complex structure [WO(OH) 4 (OH 2 )] like octahedra with four [-OH] groups in the equator plane (Eq. ( 3)) [10,33]:…”

“…These [WO(OH) 4 (OH 2 )] complex structures will then aggregate via oxolation reaction to form monoclinic WO 3 • 2H 2 O and orthorhombic WO 3 •H 2 O structures even at RT (Eqs. ( 4) and ( 5)) [10,[33][34][35].…”

“…. Recent developments in designing and controlling WO 3 nanostructure preparation have made these potentials more appealing for researchers and engineers [1][2][3][4][5][6][7][8][9][10]. Up to now, tungsten oxide has been prepared by various methods, which can be named as sol-gel [11], physical vapor ©2022 Vietnam Academy of Science and Technology deposition [12], pulsed laser deposition [13], solvothermal [14], hydrothermal [9,15], or electrospinning [16].…”

Controlled Growth of WO3 Photoanode under Various pH Conditions for Efficient Photoelectrochemical Performance

“…Tungsten trioxide hydrates (WO 3 ·nH 2 O, n = 0.33, 1, or 2) and tungsten trioxides (WO 3 ) have been widely investigated due to their diverse crystal structures and intriguing electrochemical and photovoltaic properties [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. In particular, WO 3 has been considered as a promising semiconductor material for water splitting applications via a photoelectrochemical method, because it is stable and non-toxic, and its band gap is also suitable for visible light absorption [ 12 , 14 , 16 , 21 , 22 , 23 ].…”

“…In general, WO 3 ·nH 2 O has been prepared through the solution-phase synthesis, and the WO 3 has been obtained after removing water molecules from WO 3 ·nH 2 O using calcination processes [ 24 , 25 , 26 ]. Thus, many efforts have been exerted on WO 3 ·nH 2 O and WO 3 nanostructures to develop suitable preparation methods for efficient photoelectrode applications, including acid precipitation and a hydrothermal process, by controlling the morphology, crystal structure, and growth direction at room or moderate temperatures [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 27 , 28 ]. However, to the best of our knowledge, there has been no report on the relationship between the structural evolution of WO 3 ·nH 2 O and its effect on the electrochemical performance of WO 3 photoanodes while controlling the crystal structure of WO 3 ·nH 2 O.…”