Abstract

Background: Even though silver decorated reduced graphene oxide (Ag-rGO) shows maximum absorptivity in the UV region, most of the research on the degradation of dyes using Ag-rGO is in the visible region. Therefore the present work focused on the photocatalytic degradation of indigo carmine (IC) dye in the presence of Ag-rGO as a catalyst by UV light irradiation.

Methods: In this context, silver-decorated reduced graphene oxide hybrid material was fabricated and explored its potential for the photocatalytic degradation of aqueous IC solution in the UV region. The decoration of Ag nanoparticles on the surface of the rGO nanosheets is evidenced by TEM analysis. The extent of mineralization of the dye was measured by estimating chemical oxygen demand (COD) values before and after irradiation.

Results: The synthesized Ag-rGO binary composites displayed excellent photocatalytic activity in 2 Χ 10^-5 M IC concentration and 5mg catalyst loading. The optical absorption spectrum of Ag-rGO showed that the energy band-gap was found to be 2.27 eV, which is significantly smaller compared to the band-gap of GO. 5 mg of Ag-rGO was found to be an optimum quantity for the effective degradation of IC dye. The degradation rate increases with the decrease in the concentration of the dye at alkaline pH conditions. The photocatalytic efficiency was 92% for the second time.

Conclusion: The impact of the enhanced reactive species generation was consistent with higher photocatalytic dye degradation. The photocatalytic mechanism has been proposed and the hydroxyl radical was found to be the reactive species responsible for the degradation of dye. The feasibility of reusing the photocatalyst showed that the photocatalytic efficiency was very effective for the second time.

Keywords: Chemical oxygen demand, indigo carmine, silver decorated reduced graphene oxide, photodegradation, spectrum, UV region.

Graphical Abstract