Manganese oxide nanofoam prepared by pulsed laser deposition for high performance supercapacitor electrodes

Tuning the morphology of manganese oxide nanostructures for obtaining both high gravimetric and volumetric capacitance

“…From the above discussion we know that the pressure in the PLD chamber determines the microstructure of the deposited materials, for example, thin films can be obtained in vacuum 53 and the nanofoam can be formed with 5 Torr of O 2 . 41 Thus, it is simple to tune the density of the deposited materials gradually by changing the pressure in the PLD chamber. For the samples prepared in this work, the thickness measured with the crosssection SEM images and the density calculated with the mass and the volume as a function of gas pressure are shown in Fig.…”

“…When the O 2 pressure increased to 2.0 Torr, the microstructure was nanofoam-like with a very low density, as reported before. 41 The nanofoam was constructed by nanofilaments, which were assemblies of nanoparticles. The thickness of this sample was as high as B25 mm although it had less material compared with other samples.…”

“…Detailed microstructural studies demonstrate a crystalline structure of similar MO samples. 41 After understanding the morphology and the oxidation states, we studied the supercapacitive properties by cyclic voltammetry (CV) in a 0.1 M Na 2 SO 4 aqueous solution with a three-electrode system. The representative CV curves of the MO electrodes over a range of scan rates from 5 to 350 mV s À1 could be found in the ESI.…”

“…[36][37][38] This technique is used to synthesize MO electrodes as well. [39][40][41][42] Yang synthesized MOs using manganese metallic and Mn 3 O 4 targets in an O 2 atmosphere with pressures ranging from 1 mTorr to 0.5 Torr and obtained crystalline phases of Mn 2 O 3 , Mn 3 O 4 and amorphous MnO x . 43 With the background gas pressures being higher than those used for the production of nanoparticles, a new type of nanostructure, namely nanofoam, can be fabricated, with a highly porous and interconnected foam-like morphology.…”

“…48 Our group recently reported the production of MO nanofoams by PLD, which showed a very large specific surface area and a high specific capacitance as electrodes in supercapacitors. 41 However, there are still several points which are unclear or can be improved for the understanding of the MO nanofoam: first, the MO nanofoam shows a large surface area but a small density, i.e., although its C s_m is high, its C s_V is quite low. Second, there is an activation process within the first 200 cycles whose mechanism is still not very clear.…”