Among the various synthetic techniques, the sonochemical method has emerged as an interesting method for fabricating different photocatalysis materials with unique photoelectrochemical (PEC) properties. In comparison with the classical method without sonication, this study examines the promoting effect of ultrasonic irradiation during the synthesis of tungsten oxide (WO3) nanoplates within short reaction times (15 and 30 min). The shorter ultrasonic reaction time (15 min) was sufficient for the uniform growth of thin and compact layers of WO3 nanoparticles (NPs) on the surface of a tungsten foil. In the classical method, however, partial cracks or patches formed when WO3 samples underwent acid treatment for either 15 min or 30 min at 90° C. The WO3 nanoplates fabricated with 15- or 30-min sonication followed by 15- or 30-min deposition (U-15/30-15/30) showed much higher photocurrent density than the WO3 samples fabricated with the classical method without sonication (C-15/30) at 90 °C. The as-prepared monoclinic WO3 with 30-min ultrasonication and 30-min deposition (U-30/30) showed a maximum photocurrent density of ∼6.51 mA/cm2 under simulated solar light at 1.8 V vs. Ag/AgCl, which was 2.12- to 2.93-fold higher than that of the two classical samples. The ultrasonic samples exhibited extraordinarily high stability for water oxidation by maintaining 98% of their initial photoactivity for 2200 sec, as compared to the low stability (66-61%) of both classical samples. The WO3 nanoplates prepared by sonication method had many advantages, such as facile synthetic route, compact, porous and uniform nanoplate morphology, decreased electron-hole pairs recombination rate and controlled oxygen vacancies for greatly enhanced PEC water splitting performance and stability over extended time.
Keywords: Defect engineering; Growth control; Nanoplate; Photoelectrocatalytic; Ultrasound; WO(3); Water splitting.
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