MnO2 film with three-dimensional structure prepared by hydrothermal process for supercapacitor

Hollow MO x -RuO2 (M = Co, Cu, Fe, Ni, CuNi) nanostructures as highly efficient electrodes for supercapacitors

“…As demonstrated by Figs 2a 3 -a 6 for hCo-RuNPs, 2b 3 -b 6 for hCu-RuNPs, 2c 3 -c 6 for hFe-RuNPs, 2d 3 -d 6 for hNi-RuNPs, and 2e 3 -e 7 for hCuNi-RuNPs, respectively, the nanoscale elemental mappings reveal that the corresponding transition metals and Ru are distributed uniformly in the shell regions. The elemental mapping assays are well in accord with the line scanning analyses of a number of hM-RuNPs in the HAADF-STEM mode (Figs 2a 7 for hCo-RuNPs, 2b 7 for hCu-RuNPs, 2c 7 for hFe-RuNPs, 2d 7 for hNi-RuNPs, and 2e 8 for hCuNi-RuNPs, respectively), which also show the uniform distribution of the corresponding transition metals and Ru throughout the shells of hM-RuNPs. The average thickness of the shells and their standard deviations, which are calculated directly from the TEM images, are 1.6 nm and 0.31 nm for hCo-RuNPs, 1.3 nm and 0.22 nm for hCu-RuNPs, 1.5 nm and 0.41 nm for hFe-RuNPs, 2.2 nm and 0.55 nm for hNi-RuNPs, and 3.4 nm and 0.98 nm for hCuNi-RuNPs, respectively.…”

“…This is an unavoidable loss of active materials, which reduces the value of maximum specific capacitance with the increase of cycle numbers and affects the cycling stability of the pesudocapacitors. Despite the cyclic-stability issue, pesudocapacitors are still appealing due to their appropriate potential windows [1], higher energy density than that of conventional carbon materials, and better stability than conductive polymers [2][3][4][5][6][7].…”

Scalable self-growth of Ni@NiO core-shell electrode with ultrahigh capacitance and super-long cyclic stability for supercapacitors

“…This present areal capacitance obtained at such a high discharge current density is also considerably higher than that of recently reported NF-based electrodes, such as Ni(OH) 2 @NF (1.6 F cm À2 at 2 mA cm À2 ), 35 NiCo 2 O 4 @NF (1.5 F cm À2 at 5 mAcm À2 ), 36 CoMoO 4 @NF (1.26 F cm À2 at 4 mA cm À2 ), 37 CoO@NF (1.23 F cm À2 at 1 mA cm À2 ) 23 and MnO 2 @NF (0.25 F cm À2 at 1.03 mA cm À2 ). 38 Moreover, the ANF electrode exhibits an excellent rate capability with more than 55% retention of the initial capacitance as the current density increases from 8 to 20 mA cm À2 . This remarkable capacitance and rate capability of the ANF electrode can be attributed to its unique structural features: (1) a 3D Ni core with high conductivity enables efficient charge transport and accessible diffusion of the electrolyte; (2) the direct connection between the electrochemically active NiO shell and Ni core can effectively facilitate the interfacial charge transfer; and (3) the rough surface and porous architecture of the ANF electrode not only significantly increase the accessible surface area as well as active sites for redox reaction but also promote the fast intercalation and deintercalation of ions.…”

Potentiostatic and galvanostatic electrodeposition of manganese oxide for supercapacitor application: A comparison study

“…Such high capacitance value is attributed to the ions insertion/desertion within MnO 2 structure and it depends crucially on the particle size, surface area and porosity. Since then, in achieving optimized condition for the aforementioned properties, MnO 2 with different morphologies were developed, such as nanoflakes [4], nanorods [5], nanowires [6], nanopetals [7] and nanosheets [8]. In this context, the synthesis route plays a vital role in determining its morphology.…”