Abstract
ZnWO4 nanoplates with highly exposed {0 1 ¯ 1} facets were synthesized via a hydrothermal technique. The phase, morphology, and optical characteristics of ZnWO4 nanoplates were characterized with scanning electron microscopy, transmission electron microscopy, X–ray diffraction, diffuse ultraviolet–visible light (UV–Vis) reflectance spectroscopy, photoluminescence (PL) spectrophotometry, and PL lifetime spectroscopy. Optical characterizations, along with the density functional calculations, confirm that the strong blue PL band of ZnWO4 nanoplates originates from the intrinsic defects in ZnWO4 nanoplates. Furthermore, photocatalytic tests show that ZnWO4 nanoplates exhibit strong photo-oxidative capability of complete mineralization of the organic pollutant (methyl orange) in water, whereas ZnWO4 nanoparticles can only cleave the organic molecules into fragments. The superior photo-oxidative capability of ZnWO4 nanoplates can be attributed to the specific chemical bonding and stereochemistry on the exposed facets. This work demonstrates that crystal facet engineering is an efficient strategy to endow ZnWO4 with strong photo-oxidative capability.
Highlights
Zinc tungstate (ZnWO4 ) is known for its use as an efficient scintillator [1], phosphor [2], photocatalyst [3], and photoelectrocatalyst [4,5]
Steady-state and time-resolved PL analyses along with the density functional theory (DFT) calculations confirmed that the strong blue PL of ZnWO4 nanoplates originated from the intrinsic defects in ZnWO4 nanoplates
Our photocatalytic tests showed that ZnWO4 nanoplates exhibited strong photo-oxidative capability, completely mineralizing the methyl orange molecules, whereas ZnWO4 nanoparticles could only break the organic molecules into fragments
Summary
Zinc tungstate (ZnWO4 ) is known for its use as an efficient scintillator [1], phosphor [2], photocatalyst [3], and photoelectrocatalyst [4,5]. Since the intermediates formed through the photocatalytic reactions are often more toxic than the original organic contaminants in waste water, it is critically important for the ZnWO4 photocatalysts to have such a strong photo-oxidative capability that they can completely mineralize these harmful intermediates. Crystal-facet-dependent photocatalytic activities were demonstrated in Fe2 O3 for water splitting [24]. This work demonstrates that crystal facet engineering is an efficient strategy to design highly photo-oxidative ZnWO4 photocatalysts
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