Enhancement of Photocatalysis of TiO2 by EDTA-assisted Sol-Gel Synthesis for Removal of Organic Pollutants from Aqueous Solution under Visible Light Irradiation

Abstract

In this study, a simple EDTA-Na2 assisted - sol-gel approach was applied to fabricate novel N-Ti3+ co-doped porous titanate-TiO2 rod-like heterostructures with both enhanced adsorption ability and visible light photocatalytic activity. EDTA-Na2 was found to alter the condensation pathway of the titanium precursor. This study also identified the different loading effects of EDTA-Na2 on the adsorption and photocatalytic degradation. The heterostructure with 1.0 at. % loading of EDTA-Na2 exhibited moderate adsorption ability, but high photocatalytic activity, which was attributed to the low recombination rate of photo-induced charge carriers. We also investigated the effect of calcination temperature on the physical properties and visible light photocatalytic activity of the heterostructures. When calcined at high temperature (> 400 oC), the rod-like heterostructures became thermally less stable due to the structural conversion of the visible-light-active composite (Na2Ti3O7 – anatase rod-like heterostructures) into the visible-light-inactive form (Na2Ti3O7 - Na2Ti6O13 heterostructures). High mesoporosity, low recombination rate of electrons and holes, and effective incorporation of nitrogen dopants and Ti3+ defects were the main features of the enhanced photocatalytic activity of the rod-like heterostructures in the degradation of methylene blue (MB) under visible light. .O2- was the dominated radical for MB photodegradation.