Synthesis and characterization of mesoporous silica-MnO2 nanocomposite – An efficient nanocatalyst for Methylene blue degradation

Abstract

In the present study, shell-type mesoporous silica-manganese dioxide (MPS-(MnO2)) nanocomposite was prepared and subsequently assessed for photodegradation of Methylene blue (MB) in synthetic solution under visible light. Electron micrographs show that MPS-(MnO2) composite was spherical and the average particle size was ∼180 nm. Elemental composition analysis endorses the existence of Si, Mn and O in MPS-(MnO2) composite, and sharp X-ray diffraction pattern at (113) indicates the crystalline phase of MPS-(MnO2) nanocomposite. SiO2 doping decreased the band gap of MnO2 from 2.05 to 1.98 eV, which increased the visible light absorption of MPS-(MnO2) nanocomposite. In Nyquist plots, semicircle at high frequency area indicates that MPS-(MnO2) nanocomposite has high charge transfer rate compared with MnO2 and SiO2. Similarly, semi-oval cyclic voltammogram confirms the high specific capacitance of MPS-(MnO2) compared to bare MnO2. Under optimized conditions (30 mg/L initial MB concentration, catalyst dose 75 mg/100 mL and pH 9), the MPS-(MnO2) nanocomposite degraded 89.4% of MB from synthetic solution.