MnO2 nanospheres electrode composed of low crystalline ultra-thin nanosheets for high performance and high rate supercapacitors

Amorphous MnOx Nanostructure/Multiwalled Carbon Nanotube Composites as Electrode Materials for Supercapacitor Applications

“…The FTIR results of the synthesized AMO-S and AMO/MWCNT nanocomposites are presented in Figure b. The presence of surface adsorbed water in all the samples can be revealed by the characteristic broad absorption peaks at around 3398/3409/3412 cm –1 (associated with the O–H stretching modes of vibrations). ,, The peaks at ∼1622/1623/1626 cm –1 and ∼1230/1233 cm –1 can be assigned to the −CO and C–O–C stretching modes of surface embedded CD-S molecules, respectively. , The peaks centered at ∼1531/1532/1535 cm –1 and ∼1419/1424/1428 cm –1 can be assigned to the O–H bending modes of bound water present in the amorphous MnO x lattice. , The peaks corresponding to ∼514/511 cm –1 and ∼756 cm –1 are ascribed to the Mn–O bending and stretching vibrations, respectively. ,, The FTIR spectrum of AMO-Suc (Figure S2b) resembles with the AMO-S sample. Moreover, the FTIR spectra of both the AMO/MWCNT nanocomposites indicate similar profiles like AMO-S with a slight shift of some peak positions, suggesting that the nanocomposites have major proportions of amorphous MnO x phase.…”

“…The charge storage process of MnO 2 -based electrode materials in mild aqueous electrolytes containing monovalent cations (C + = Li + , Na + , K + etc.) can be described by the following one electron Faradaic redox reaction: which may occur on the surface via adsorption–desorption of protons (H + )/ C + and into the bulk solid via insertion-extraction of H + / C + . , Disordered nanostructures of amorphous MnO x (AMO) have shown particular interest in the electrochemical energy storage and conversion applications like lithium/zinc-ion batteries − and supercapacitor. ,− Lack of proper grain boundary and long-range structural order, presence of abundant defect centers, and large accessible active sites due to the high specific surface area of AMO may be advantageous for the rapid ionic (H + / C + ) diffusion, shorter diffusion path, and structural flexibility to accommodate volume expansion/contraction during the electrochemical intercalation–deintercalation process. ,, The structural disorder in the AMO may reduce scattering mean free path of ions and provides more accessible channels for faster ionic transportation . Also, the synthetic conditions of AMO are gentle and usually involve low-temperature solution-based techniques compared to that of the well-crystalline counterparts. ,,− To achieve high performance electrode material, carbon nanotubes (CNTs) are frequently integrated with MnO 2 as a conductive current collector to overcome electronic transport limits by facilitating a transportation path of charge from redox active sites to the external circuit. ,, Several observations based on the MnO x /CNT composite electrode materials are noteworthy from the literature.…”

“…The presence of surface adsorbed water in all the samples can be revealed by the characteristic broad absorption peaks at around 3398/3409/3412 cm −1 (associated with the O−H stretching modes of vibrations). 15,34,46 The peaks at ∼1622/1623/1626 cm −1 and ∼1230/1233 cm −1 can be assigned to the −CO and C−O−C stretching modes of surface embedded CD-S molecules, respectively. 34,46 The peaks centered at ∼1531/ 1532/1535 cm −1 and ∼1419/1424/1428 cm −1 can be assigned to the O−H bending modes of bound water present in the amorphous MnO x lattice.…”

“…34,46 The peaks centered at ∼1531/ 1532/1535 cm −1 and ∼1419/1424/1428 cm −1 can be assigned to the O−H bending modes of bound water present in the amorphous MnO x lattice. 15,46 The peaks corresponding to ∼514/511 cm −1 and ∼756 cm −1 are ascribed to the Mn−O bending and stretching vibrations, respectively. 15,33,46 The FTIR spectrum of AMO-Suc (Figure S2b) resembles with the AMO-S sample.…”

“…15,46 The peaks corresponding to ∼514/511 cm −1 and ∼756 cm −1 are ascribed to the Mn−O bending and stretching vibrations, respectively. 15,33,46 The FTIR spectrum of AMO-Suc (Figure S2b) resembles with the AMO-S sample. Moreover, the FTIR spectra of both the AMO/ MWCNT nanocomposites indicate similar profiles like AMO-S with a slight shift of some peak positions, suggesting that the nanocomposites have major proportions of amorphous MnO stretching vibrations of octahedral MnO 6 unit).…”