Urea-assisted hydrothermal synthesis of manganese dioxides with various morphologies for hybrid supercapacitors

MnO2 samples (MO-1 with thorn spheres and MO-2 with long nanowires) were synthesized by adding urea into KMnO4-acid reaction system. Urea was added to decrease the reaction temperature for its weak reducibility. Moreover, hydrolysis of urea influenced the morphologies of MnO2. AC//MO-2 hybrid capacitors exhibited better capacitive properties than AC//MO-1 due to two factors: (i) the smaller resistance of MO-2 and (ii) the Faradaic reactions occurring on the surface and in the bulk of MO-2 which was rarely reported.220