Microporous vanadosilicate films with tailorable V4+/V5+ ratio to achieve enhanced visible-light photocatalysis

Abstract

This study investigates the changes induced into the photocatalytic activity under solar light irradiation upon changing the structural film properties and tailor the concentration of defects in microporous vanadosilicate AM-6 films. For this purpose, the preparation of AM-6 films with different V4+/V5+ ratios and their utilization as photocatalysts for the decomposition of MB were carried out. Two approaches were used for obtaining AM-6 films with different V4+/V5+ ratios: altering the seed layer coating technique and altering the molar water content of the secondary growth gel. It was seen that dip coating method resulted in an increase in the thickness of the films and it was presumed that the adsorption of MB by AM-6 films was the predominant factor in photocatalytic activity. The second approach of increasing the molar water content of the secondary growth gel provided an increase in the defect concentration resulting in an enhanced photocatalytic activity under the solar light. In the current study, the defect concentration of the prepared films was determined by using XPS and Raman spectroscopy techniques. Accordingly, it was determined that the samples with lower amount V4+/V5+ ratio showed better photocatalytic activity under the solar light irradiation indicating that V5+ cations are responsible for the photocatalytic activity under visible light irradiation. This work provides methods of production of microporous films showing photocatalytic activity under visible light without the requirement of any post-synthesis treatments.