Unlocking the effect of Zn on crystal structure, optical properties, and photocatalytic degradation of perfluoroalkyl substances (PFAS) of BiWO

• Published in: Environmental science water research & technology 2023-10, Vol.9 (11), p.2866-2879
• Main Authors: Hojamberdiev, Mirabbos, Larralde, Ana Laura, Vargas, Ronald, Madriz, Lorean, Yubuta, Kunio, Sannegowda, Lokesh Koodlur, Sadok, Ilona, Krzyszczak-Turczyn, Agnieszka, Oleszczuk, Patryk, Czech, Bo ena
• Format: Article
• ISSN: 2053-1400; 2053-1419
• DOI: 10.1039/d3ew00430a

Bismuth tungstate (Bi 2 WO 6 ) with a layered structure and visible light response exhibits excellent photocatalytic activity. To enhance its photocatalytic activity for the degradation of perfluoroalkyl substances (PFAS), Zn 2+ is partially substituted for Bi 3+ in the Bi 2 WO 6 lattice in this study. Particularly, the effect of Zn 2+ content (0-22.5 at%) on the crystal structure, optical property, and photocatalytic activity for the photodegradation of PFAS of Bi 2 WO 6 is investigated. According to the Le Bail fits, the unit-cell volume is slightly reduced from 487.7 Å 3 to 480.8 Å 3 by the partial substitution of smaller Zn 2+ (0.74 Å for CN = 6) for larger Bi 3+ (1.03 Å for CN = 6) in the Bi 2 WO 6 crystal lattice, and the solubility of Zn 2+ in the Bi 2 WO 6 lattice is found to be below 17.5 at%. The partial substitution of Zn 2+ influences the self-aggregation of nanoparticles, Ostwald ripening, and self-organization of nanoplates, resulting in different morphologies. Although the optical bandgap energy of Bi 2 WO 6 is not significantly altered upon the partial substitution of Zn 2+ , the conduction and valence bands simultaneously shift upward. Among the Bi 2− x Zn x WO 6+ δ photocatalysts, 2.5 at% Zn 2+ -substituted Bi 2 WO 6 exhibits larger water oxidation photocurrent density (0.316 mA cm −2 at 1.23 V RHE ) and the highest photocatalytic activity for the photodegradation of PFH x A ( k 1 = 0.012 min −1 ). The trapping experiments confirm that the photo-excited holes (h + ) and superoxide radicals (O 2 &z.rad; − ) are the major reactive species involved in the photodegradation of PFH x A. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF/MS) reveals that decarboxylation and defluorination are the main possible routes for the photodegradation of PFH x A over Bi 2− x Zn x WO 6+ δ photocatalysts. Our findings suggest that the partial Zn 2+ -to-Bi 2+ substitution can enhance the photocatalytic activity of Bi 2 WO 6 for the degradation of PFAS. The effect of Zn 2+ on the crystal structure, optical properties, and photocatalytic activity for degradation of perfluoroalkyl substances of Bi 2 WO 6 was studied.