The Effect of Defects Created in Microporous Vanadosilicate AM-6 Thin Films in Photocatalysis

Micro and Nanotechnology Department, Middle East Technical University, Ankara, , Turkey The development of visible-light effective photocatalysts allows low cost degradation of toxic non-biodegradable organic pollutants. Vanadium, present in a specific oxidation state within the structure of SiO2 matrix could open up the gateway to investigate and tailor the defects created for such photocatalytic applications. Vanadosilicate AM-6, which is a large pore microporous material containing semiconducting monatomic …V-O-V-O-V… chains embedded in a silica matrix has recently been demonstrated to exhibit photocatalytic activity in the visible light range. Pore regularity, control of defects, and the presence of stoichiometric amounts of in AM-6 allows one to create alternative materials in visible-light photocatalysis. Accordingly, vanadosilicate AM-6 thin films with controlled defect sites were produced by tailoring the V5+/V4+ ratio within the thin film structure . Furthermore, the effect of changing molar composition and vanadium source used for the secondary growth was also investigated systematically. V5+/V4+ ratio was tailored systematically by controlling the defect concentration of seed crystals during the film growth and vanadium source with alternating V5+ concentration. It was found that vanadosilicate AM-6 films with higher amount of V5+ ions arising from 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. Photocatalyst production in the form of thin film provides integration of the material to device-oriented applications and also accelerates the degradation kinetics between the pollutant and the photocatalyst due to the controlled defect formation leading to enhanced photocatalytic activity under visible light