The Effect of Sr-Doping on Structural, Optical, Catalytic, and Photocatalytic Properties of α-MnO2 Nanowires Synthesized via a Hydrothermal Route

Undoped and Sr-doped -MnO2 nanowires were synthesized through hydrothermal method to be used as catalyst and photocatalyst for the degradation of Methylene Blue (MB) dye. The Sr concentrations were 2, 4, 6 and 8 wt%. X-ray diffraction demonstrated the synthesis of the -MnO2 tetragonal phase with large tunnels along c-axis in which Sr dopant is incorporated. FT-IR and Raman spectroscopy confirmed the synthesis of -MnO2. The SEM microscopy showed that -MnO2 crystallites have nanowire morphology with length up to 5.91 µm. Optical investigation demonstrated that the -MnO2 nanowires have a band gap which slightly decreases with increasing Sr concentration and photoluminescence exhibits emission bands in visible region. The evaluation of catalytic and photocatalytic activity of -MnO2 nanowires was conducted against Sr concentration, the results demonstrated a high efficiency in the catalytic degradation of MB which reached in only 2 min 49.93% for undoped sample and is almost total 99.63% for the highly doped sample. Under UV irradiation (=365 nm), the photocatalytic degradation by undoped sample is more important and reached 97.74% in 60 min. The effect of UV irradiation, size, morphology and Sr doping of -MnO2 nanowires greatly improved the degradation of MB and led to its mineralization.