Submicrometer colloidal nanocrystal assemblies (CNAs) of MnFeO have been synthesized solvothermally and have been sued as the electrode materials for Lithium ion batteries. Large MnFeO CNAs, which were prepared with the assistance of CHCOONH, possessed the size of about 950 nm showed a larger pore size but a smaller specific surface area, compared with that of 160 nm MnFeO CNAs with the help of CHCOONa•3HO. The capacitance of MnFe-NH can reach 1200 mAh g at the first circle at the current density of 0.1 A g. However, the capacitances were decreased drastically under the further measurements. MnFe-Na showed about 50 mAh g lower capacity and worse cycle stability than MnFe-NH. Cyclic voltammetry and electrochemical impedance spectroscopy profile indicated the higher electronic conductivity of MnFe-NH, thanks to the larger size of primary crystalline particle and interspace between them.
Amphiphilic organic ligands, 5-octadecyloxy-2-(2-pyridylazo)phenol (PARC18) and 1,10-bis[3'-hydroxy-4'-(2' '-pyridylazo)phenoloxy]decane (PAR)2C10, are coordinated with Cu(II) ions, resulting in two complexes. Scanning tunneling microscopy (STM) images provide direct structural evidence for the coordination from organic ligands to resulted complexes. The appearance and conformation differences in ligands and corresponding complexes can be clearly seen in STM images recorded from their self-organizations on highly oriented pyrolytic graphite (HOPG). The adlayer structures of PARC18−Cu and (PAR)2C10−Cu complexes are significantly different from those of their corresponding ligands. A phase separation is found in the adlayer formed with the PARC18 ligand and its complex. The results demonstrate that STM is a powerful tool in coordination chemistry in analyzing ligand and coordinated complex. The coordination from ligands to complexes with metal ions would be a facile approach to surface modification and functional two-dimensional (2D) assembly fabrication.
Abstract Composite microspheres consisting of molybdenum disulfide, amorphous carbon, and reduced graphene oxide (named MoS 2 ‐AC‐RGO) were prepared by using a hydrothermal approach combined with the spraying coagulation process and calcinations step. Intercalation compound cellulose−MoS 2 was obtained after the spraying coagulation‐assisted hydrothermal treatment, which then converts to MoS 2 ‐AC‐RGO after calcination. Graphene oxide and cellulose were utilized as the precursors of RGO and AC, respectively. Thiourea was adopted as both the species for cellulose dissolution and the sulfur precursor for MoS 2 . The suspension of GO and sodium molybdate also played the role of the coagulation bath. The influence of cellulose on the structure, morphology, and electrochemical performance of the resultant MoS 2 ‐AC‐RGO microspheres was investigated based on XRD, SEM, TEM, Raman spectra, TGA, and N 2 adsorption−desorption technique as well as electrochemical measurements. The composite microspheres show superior electrochemical properties as anode materials for lithium‐ion batteries and exhibit a high reversible capacity of 910 mAhg −1 at a current density of 200 mA g −1 , excellent rate capability, and superior cyclic stability with a capacity of 86% after 70 cycles. The roles of the graphene and the cellulose in improving the electrochemical properties of the MoS 2 ‐AC‐RGO composites are discussed based on the morphology, structure, phase, and electrochemical performance studies.
Two types of manganese ferrite nanoparticles, namely MF-SA and MF-CHI, have been synthesized solvothermally from the synthesis systems containing sodium alginate and chitosan, respectively. Both MF-SA and MF-CHI showed well crystalline nature based on the XRD and TEM measuremants. The larger saturation magnetization value of MF-SA should be ascribed to its slightly larger crystallite size than that of MF-CHI. Results from N adsorption-desorption isotherms and Raman spectra confirmed the structural difference in MF-SA and MF-CHI. The electrocapacitive behavior of manganese ferrite-based supercapacitors has been studied and MF-SA displayed a specific capacitance of around 60.4 F•g at 0.25 A•g in aqueous symmetric supercapacitors, larger than that of MF-CHI about 45.1 F•g at the same condition. MF-SA based supercapacitor also showed better capacitance maintenance of around 82% of the initial value at 1 A•g after 2000 cycle test than that of MF-CHI based cells. Based on the experimental data, the structure-property relationship of two types of MnFeO nanoparticles have been discussed and analyzed.
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