Hydrothermal synthesis of cubic MnSe2 and octahedral α-MnSe microcrystals

Hybrid Reduced Graphene Oxide/Manganese Diselenide Cubes: A New Electrode Material for Supercapacitors

“…Interestingly, such oxide peaks were not observed for the G‐MnSe 2 hybrid material. The calcination method suggested by Liu et al . was used to remove the small amount of Se impurities from MnSe 2 , and XRD indicated the removal of the selenium impurities.…”

“…[35] These two peaks confirmed the presenceo fS e 2À ions in MnSe 2 .I na ddition to these peaks, MnSe 2 (calcined at 230 8Cf or 15 min) has an additional peak at ab inding energy of 58.41 eV, [35] which was attributed to the formationo fS eO 2 during calcination.I nterestingly,s uch oxide peaks were not observed for the G-MnSe 2 hybrid material. Thec alcination method suggested by Liu et al [22] was used to remove the small amount of Se impurities from MnSe 2 ,a nd XRD indicated the removal of the seleniumi mpurities.I nc ontrast to the XRD observations,X PS confirmed the presence of selenium in the form of an oxide (SeO 2 ). Therefore,a fter the samplew as heated to the melt- [29] Thee lectrochemicalp erformances of the as-synthesized electrodem aterials (MnSe 2 and G-MnSe 2 )w ere evaluated in at wo-electrodes ymmetric-cell configurationw itha na queous 0.5 m H 2 SO 4 electrolyte.T he specific capacitance of the cell (C c )a nd the correspondings pecific capacitance of as ingle electrode( C E )w ere determined by cyclic voltammetry (CV) and charge-discharge (CD) measurements.T he CV curveso fM nSe 2 -a nd G-MnSe 2 -based symmetric cells measured at as can rate of 25 mV s À1 are comparedi nF igure 5a.…”

“…For comparative purposes, pure MnSe 2 was also synthesized by a similar method without the addition of GO. An attempt was made to eliminate selenium impurities by calcining the sample at 230 °C for 15 min in air according to the methodology reported by Liu et al …”

“…Liu et al. attempted to remove the selenium impurity by baking their final MnSe 2 product at 503 K for 15 min . For this removal method, no selenium impurity peaks were observed in the X‐ray diffraction (XRD) pattern; in contrast, a strong SeO 2 peak was oserved by X‐ray photoelectron spectroscopy (XPS) using the method proposed by Liu et al.…”

“…[21] Ther emoval of seleniumi mpurities from the final MnSe 2 product has not been investigated by many researchers.L iu et al attempted to removethe selenium impurity by baking their final MnSe 2 product at 503 K for 15 min. [22] Fort his removal method, no seleniumi mpurity peaks were observed in the X-ray diffraction (XRD) pattern; in contrast, as trong SeO 2 peak was oserved by X-rayp hotoelectron spectroscopy (XPS)u sing the methodp roposed by Liu et al Therefore,t his calcination methodd id not remove the seleniumi mpurity completely;i nstead, the selenium might have been converted to an amorphous phase that could not be observed by XRD.…”