Ag@Mn_xO_y: an effective catalyst for photo-degradation of rhodamine B dye

Water pollution by the textile industry is a major issue. Therefore, there is a need for methods to remove organic dyes from industrial effluents. Various metal oxides have been used as catalysts for the degradation of dyes. The catalytic efficiency of metal oxides can be enhanced by doping metal oxides with metals. Here we report the synthesis and characterization of nano-sized mixed valence manganese oxide (Mn_xO_y) and silver-doped mixed valence manganese oxide (Ag@Mn_xO_y). We study their photo-catalytic efficiency for the photo-degradation of the rhodamine B dye under light irradiation. Mn_xO_y was prepared using KMnO₄, MnSO₄ and NH₃, and Ag@Mn_xO_y was prepared using AgNO₃ and Calotropis gigantea plant extract. The prepared materials were characterized by X-ray diffractometry, scanning electron microscopy and Fourier transform infrared spectroscopy. Results show that doping with Ag enhanced the photo-catalytic performance of Mn_xO_y from 11 to 28% and 45 to 91% degradation of rhodamine B dye in 15 and 120 min, respectively. This enhancement is explained by the fact that Ag doping prevents the recombination of photoexcited electrons and positive holes, thus enhancing the photo-catalytic activity of Mn_xO_y.