Birnessite-MnO2nanostructures synthesized by facile hydrothermal and green method for dye degradation application

•Birnessite manganese dioxide nanostructures prepared using “green” and hydrothermal methods.•Optimum reaction temperature for both synthesis method found to be low at 90 °C.•Photodegradation of methyl orange dye shows effective degradation which is more prominent for green synthesized sample.•Decolouration of methyl orange enhanced by using the δ-MnO2nanocatalyst in acidic pH.