Photocatalytic and Optical Modulation of δ-MnO2 Nanoflowers with Surface Morphology and Disorder

In this work, the δ polymorph of MnO
2
nano-flowers (NFs) with two different surface morphologies were hydrothermally synthesized by changing the cooling technique. The slow oven-cooled NFs exhibited superior photocatalytic efficiency than the fast air-cooled ones. The structural and optical study revealed a reduction in effective optical band gap with an enhanced growth of nano-petal-like structures on MnO
2
particle surfaces for the slow cooling process. The augmentation observed in photo-degradation kinetics was explicated in terms of a change in surface texturing associated with nano-petal growth and defect-induced destabilization of excitons.