Room Temperature Synthesis Routes to the 2D Nanoplates and 1D Nanowires/Nanorods of Manganese Oxides with Highly Stable Pseudocapacitance Behaviors

The 2D nanoplates of delta-MnO2 and the ID nanowires/nanorods of alpha-MnO2 can be synthesized at room temperature via one-pot oxidation reaction of commercially available divalent manganese compounds. Treating the MnO or MnCO3 precursor with persulfate ions for 1-2 days yields layered delta-MnO2 2D nanoplates, whereas the same oxidation reaction for the MnSO4 precursor produces gamma-MnO2-structured 3D urchins. As the reaction time is extended for similar to 14-21 days, not only delta-MnO2 nanoplates but also gamma-MnO2 urchins are changed to well-separated ID nanostructured alpha-MnO2 materials with controllable diameters. According to N2 adsorption-desorption isotherm measurements and Mn K-edge X-ray absorption spectroscoyy, all the obtained manganate nanostructures show expanded surface areas of similar to S0-120 m(2) g(-1) the mixed oxidation state of Mn3+/Mn4+, respectively. All the present nanostructured manganese oxides exhibit pseudocapacitance behaviors with large specific capacitance and excellent capacitance retention, highlighting their promising functionality as a supercapacitor electrode. Among the materials under investigation, the delta-MnO2 2D nanoplates show the largest specific: capacitance (similar to 180-210 F g(-1)). The present finding clearly demonstrates that the room-temperature oxidation reaction of the MnO or MnCO3 precursor can provide a facile soft-chemical route to 2D delta-MnO2 nanoplates and ID alpha-MnO2 nanowires/nanorods with highly stable pseudocapacitance behaviors.