Fast Morphological Evolution and Enhanced Capacitive Behavior of MnO_2 at High Operating Temperature

摘要

Amorphous nanostructured MnO_2 was anodically deposited onto duplex stainless steel substrate. The cyclic stability of MnO_2 wasinvestigated by chronopotentiometry in 1 M Na_2SO_4 at two different temperatures. Results demonstrated that the specific capacitancewas enhanced significantly after 2000 cycles at 70°C, from the initial of 624 F g~(-1) to the final of 1158 F g~(-1), and maintained at about900 F g~(-1) during the next 1000 cycles at 30°C. This specific capacitance improvement was ascribed to the enlarged specific surfacearea caused by drastic morphological evolution from worm-like nanorods to leaf-like nanosheets confirmed by scanning electronmicroscopy.