Fabrication of Ag2O/TiO2 composites on nanographene platelets for the removal of organic pollutants: Influence of oxidants and inorganic anions

Ternary Ag₂O/TiO₂/nanographene platelet (Ag₂O/TiO₂/NGP) composites containing various amounts of NGP were synthesized using a microwave-assisted method and were used as catalysts for degradation of organic dyes in aqueous solution. The composites were characterized by various methods, and their photocatalytic performance was systematically investigated with respect to degradation of methylene blue. Compared with pure TiO₂ and Ag₂O nanoparticles as well as Ag₂O/TiO₂ composites, the Ag₂O/TiO₂/NGP composites exhibited superior photocatalytic performance in the UV and visible light range. The results also indicated that Ag₂O/TiO₂/NGP composites could be used as efficient broad-spectrum catalysts for the removal of several dye contaminants in aqueous solutions. The correlation between photocatalytic mechanism and physical properties of the catalysts was discussed. The effects of the addition of hydrogen peroxide (H₂O₂) and persulfate on MB degradation were also investigated. Photocatalytic efficiency was noticeable in the presence of both oxidizers. Because inorganic anions are common substances in natural water, their influence was also evaluated. They were found to inhibit the catalytic activity of Ag₂O/TiO₂/NGP composites. Their effectiveness in inhibiting photocatalytic degradation of MB was CO₃²⁻ > NO₃⁻ > HPO₄⁻ > Cl⁻ > SO₄²⁻.