Photocatalysis

Pore regularity, control of defects, and the presence of stoichiometric amounts of vanadium in the silicate framework allows one to create alternative materials in advanced applications such as photocatalysis. Vanadium present in specific form within the structure of SiO2 matrix could open the gateway to investigate and tailor the defects created for specific catalytic applications. For that reason, vanadosilicate AM-6 containing 1-dimensional, semiconducting, and quantum-confined ...V-O-V-O-V... chains can be a very interesting material with tailorable defect sites in photocatalysis. It is known that vanadosilicate AM-6 containing ...V-O-V-O-V... chains have photocatalytic activity under visible light irradiation [1, 2]. This makes vanadium silicate AM-6 a natural sunlight photocatalysts. The aim of this study is to investigate the photocatalytic behavior of vanadium silicate AM-6 in thin film form as a photocatalyst for the degradation of methylene blue (MB) and to enhance its photocatalytic activity applying various modifications to the samples.

Accordingly, vanadosilicate AM-6 thin films with controlled defect sites were prepared on the ITO coated glass substrates using secondary growth method by tailoring the ratio of V5+/V4+ ratio within the thin film structure. It was shown that the utilization of different vanadium sources and/or the molar compositions of the secondary growth solution affect the quality of thin films leading to alterations in the V5+/V4+ ratio. It was found that vanadosilicate AM-6 films with higher amount of V5+ ions arising from seed layer or different synthesis conditions possess better photocatalytic activity under visible light irradiation for the degradation of MB, which can be attributed to the presence of V5+ cation within the framework of AM-6. Integration of noble metal nanoparticles was used as a way for enhancing the photocatalytic activity of AM-6. It was thought that Ag loading extends the light absorption and surface electron excitation causing enhanced photocatalytic activity. Photocatalysts production in thin form provides integration of the material to device-oriented applications and accelerates the degradation kinetics due to the increase of the contact surface area between the pollutant and the photocatalyst increasing the photocatalytic activity.