Effect of reaction time on the phase transformation and photocatalytic activity under solar irradiation of tungsten oxide nanocuboids prepared via facile hydrothermal method

ABSTRACT

Monoclinic WO₃ nanocuboids were synthesized via a one-pot hydrothermal method in a highly acidic environment at 180°C for different reaction times (12, 24, and 48 h). The phase transformation from orthorhombic to monoclinic and then to oxygen-deficient Magnéli phase and an increase in optical bandgap from 2.43 to 2.70 eV were observed when the reaction time increased from 12 to 24 h and then to 48 h. All samples showed photocatalytic activity towards the degradation of methylene blue (MB) under solar light irradiation, which was strongly enhanced in the presence of hydrogen peroxide (H₂O₂). Sample prepared for 24 h showed the highest MB removal efficiency of 31.4% in the absence of H₂O₂, which was enhanced to 76% and 92% when adding 0.2 and 0.5 mL of H₂O₂, respectively. These results give insights into the phase transformation and photocatalytic mechanism of WO₃ nanocuboids prepared via the hydrothermal method.

KEYWORDS:

• Tungsten oxide nanocuboids
• hydrogen peroxide
• phase transformation
• hydrothermal
• photocatalyst
• solar light irradiation

Acknowledgments

This research was funded by the Vietnam Ministry of Education and Training under Grant number B2020-BKA-19. We gratefully acknowledge the fruitful discussions with N. D. Chien. The authors thank the support from the BKEMMA at the AIST-HUST for the FESEM work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was funded by the Vietnam Ministry of Education and Training under Grant number B2020-BKA-19.