| 2. |
- Jayaramulu, K., et al.
(författare)
-
Covalent Graphene-MOF Hybrids for High-Performance Asymmetric Supercapacitors
- 2021
-
Ingår i: Advanced Materials. - : Wiley-VCH Verlag. - 0935-9648 .- 1521-4095. ; 33:4
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, the covalent attachment of an amine functionalized metal-organic framework (UiO-66-NH2 = Zr6O4(OH)4(bdc-NH2)6; bdc-NH2 = 2-amino-1,4-benzenedicarboxylate) (UiO-Universitetet i Oslo) to the basal-plane of carboxylate functionalized graphene (graphene acid = GA) via amide bonds is reported. The resultant GA@UiO-66-NH2 hybrid displayed a large specific surface area, hierarchical pores and an interconnected conductive network. The electrochemical characterizations demonstrated that the hybrid GA@UiO-66-NH2 acts as an effective charge storing material with a capacitance of up to 651 F g−1, significantly higher than traditional graphene-based materials. The results suggest that the amide linkage plays a key role in the formation of a π-conjugated structure, which facilitates charge transfer and consequently offers good capacitance and cycling stability. Furthermore, to realize the practical feasibility, an asymmetric supercapacitor using a GA@UiO-66-NH2 positive electrode with Ti3C2TX MXene as the opposing electrode has been constructed. The cell is able to deliver a power density of up to 16 kW kg−1 and an energy density of up to 73 Wh kg−1, which are comparable to several commercial devices such as Pb-acid and Ni/MH batteries. Under an intermediate level of loading, the device retained 88% of its initial capacitance after 10 000 cycles. © 2020 The Authors. Advanced Materials published by Wiley-VCH GmbH
|
|
| 3. |
- Zboril, R, et al.
(författare)
-
Thermal behaviour of pyrope at 1000 and 1100 degrees C: mechanism of Fe2+ oxidation and decomposition model
- 2003
-
Ingår i: Physics and Chemistry of Minerals. - : Springer Science and Business Media LLC. - 0342-1791 .- 1432-2021. ; 30:10, s. 620-627
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanism of thermally induced oxidation of Fe2+ from natural pyrope has been studied at 1000 and 1100 degreesC using Fe-57 Mossbauer spectroscopy in conjunction with XRD, XRF, AFM, QELS, TG, DTA and electron microprobe analyses. At 1000 degreesC, the non-destructive oxidation of Fe2+ in air includes the partial stabilization of Fe3+ in the dodecahedral 24c position of the garnet structure and the simultaneous formation of hematite particles (15-20 nm). The incorporation of the magnesium ions to the hematite structure results in the suppression of the Morin transition temperature to below 20 K. The general garnet structure is preserved during the redox process at 1000 degreesC, in accordance with XRD and DTA data. At 1100 degreesC, however, oxidative conversion of pyrope to the mixed magnesium aluminium iron oxide, Fe-orthoenstatite and cristoballite was observed. During this destructive decomposition, Fe2+ is predominantly oxidized and incorporated into the spinel structure of Mg(Al,Fe)(2)O-4 and partially stabilized in the structure of orthoenstatite, (Mg,Fe)SiO3. The combination of XRD and Mossbauer data suggest the definite reaction mechanism prevailing, including the refinement of the chemical composition and quantification of the reaction products. The reaction mechanism indicates that the respective distribution of Fe(2+)and Fe3+ to the enstatite and spinel structures is determined by the total content of Fe2+ in pyrope.
|
|
