Metastable h-WO 3 nano-hemitubes: controllable synthesis and superior adsorption–photocatalysis–oxidation activity for high-concentrated MB

Novel metastable h-WO 3 nano-hemitubes have been controllably prepared on a large scale assisted by inorganic structure directing agent of (NH 4 ) 2 C 2 O 4 through a convenient and facile hydrothermal route. The chemical composition, morphology, crystal structure, surface area and optical property of as-obtained products were investigated using various characterization techniques. Interestingly, it was found that the introduction and the adding amount of (NH 4 ) 2 C 2 O 4 played an important role in the process of controlling the phase and morphology of WO 3 . An appropriate amount of (NH 4 ) 2 C 2 O 4 (10–14 mmol) was beneficial for inducing the formation of metastable h-WO 3 nano-hemitubes. However, monoclinic m-WO 3 square-shaped nanoplates were obtained by adding 2 mmol (NH 4 ) 2 C 2 O 4 . The results of photoluminescence (PL) test demonstrated that h-WO 3 nano-hemitubes has a lower recombination rate of photogenerated electron–hole pairs and a longer lifetime of photogenerated carriers. Due to the special structure, the prepared one-dimensional h-WO 3 nano-hemitubes displayed very superior adsorption–photocatalysis–oxidation activity for removing MB from highly concentrated MB-containing wastewater, which was 6.1 times higher than that of two-dimensional monoclinic m-WO 3 square-shaped nanoplates. The mechanism of adsorption–photocatalysis–oxidation degradation for MB on h-WO 3 nano-hemitubes was simply proposed. The prepared h-WO 3 nano-hemitubes may have a potential application in wastewater purification and environmental remediation.