To improve both oxygen evolution efficiency and stability at high temperatures, Mn, Mn+Mo, Mn+Mo+V, and Mn+Fe+V oxide electrodes were prepared on a Ti substrate, with an intermediate layer of IrO_2, by an anodic depos...To improve both oxygen evolution efficiency and stability at high temperatures, Mn, Mn+Mo, Mn+Mo+V, and Mn+Fe+V oxide electrodes were prepared on a Ti substrate, with an intermediate layer of IrO_2, by an anodic deposition method. The crystal structure, surface morphology, pore size distribution, specific surface area, and voltammetric charge were then characterized for each electrode. The results demonstrated that for Mn-O electrodes, the preferential orientation of the(100) crystal plane and the mesopore structure played negative roles in the oxygen evolution reaction. On the basis of the electrocatalytic properties of MnO2-based electrodes in seawater, the outer surface voltammetric charge at a scan rate of 500 mV·s-1 was shown to effectively indicate whether oxygen evolution reactions were preferred over chlorine evolution reactions. The Mn-O electrode exhibited oxygen evolution efficiency of only 47.27%, whereas the Mn+Mo, Mn+Mo+V and Mn+Fe+V oxide electrodes displayed oxygen evolution efficiency of nearly 100%. This means that adding Mo, V, and Fe elements to the electrode can improve its crystal structure and morphology as well as further enhancing its oxygen evolution efficiency.展开更多
We demonstrate a simple and highly efficient strategy to synthesize MnO2/nitrogen-doped ultramicroporous carbon nanospheres（MnO2/N-UCNs） for supercapacitor application.MnO2/N-UCNs were fabricated via a template-free...We demonstrate a simple and highly efficient strategy to synthesize MnO2/nitrogen-doped ultramicroporous carbon nanospheres（MnO2/N-UCNs） for supercapacitor application.MnO2/N-UCNs were fabricated via a template-free polymerization of resorcinol/formaldehyde on the surface of phloroglucinol/terephthalaldehyde colloids in the presence of hexamethylenetetramine,followed by carbonization and then a redox reaction between carbons and KMnO4.As-prepared MnO2/N-UCNs exhibits regular ultramicropores,high surface area,nitrogen heteroatom,and high content of MnO2.A typical MnO2/N-UCNs with 57 wt.%MnO2 doping content（denoted as MnO2（57%）/N-UCNs） makes the most use of the synergistic effect between carbons and metal oxides.MnO2（57%）/N-UCNs as a supercapacitor electrode exhibits excellent electrochemical performance such as a high specific capacitance（401 F/g at 1.0 A/g） and excellent charge/discharge stability（86.3%of the initial capacitance after 10,000 cycles at 2.0 A/g） in 1.0 mol/L Na2SO4 electrolyte.The well-designed and high-performance MnO2/N-UCNs highlight the great potential for advanced supercapacitor applications.展开更多
Nanostructured MnO2/CNT composite was synthesized by a soft template approach in the presence of Pluronic P123 surfactant. The product was characterized by X-ray diffraction, thermogravimetric and differential thermal...Nanostructured MnO2/CNT composite was synthesized by a soft template approach in the presence of Pluronic P123 surfactant. The product was characterized by X-ray diffraction, thermogravimetric and differential thermal analyses, Fourier transformed infrared spectroscopy and high-resolution transmission electron microscopy. The results show that the sample consists of poor crystalline α-MnO2 nanorods with a diameter of about 10 nm and a length of 30-50 nm, which absorb on the carbon nanotubes. The electrochemical properties of the product as cathode material for Li-MnO2 cell are evaluated by galvanostatic charge-discharge and electrochemical impedance spectroscopy （EIS）. Compared with pure MnO2 electrode, the MnO2/CNT composite delivers a much larger initial capacity of 275.3 mA-h/g and better rate and cycling performance.展开更多
A novel bird nest-like nanostructured MnO2(BNNS-MnO2) was prepared by a facile and cost-effective strategy. Their structures and morphologies were characterized by field emission scanning electron microscopy, transmis...A novel bird nest-like nanostructured MnO2(BNNS-MnO2) was prepared by a facile and cost-effective strategy. Their structures and morphologies were characterized by field emission scanning electron microscopy, transmission electron microscopy and powder X-ray diffraction. Capacitive behaviors were investigated by cyclic voltammetry and galvanostatic charge-discharge. The obtained nano-MnO2 possesses a well designed loose-assembled hierarchical nanoarchitecture with an appropriate crystallinity which gives rise to excellent performances as an electrode material for supercapacitors. A maximum specific capacitance of 917 F/g has been obtained at a current density of 5 mA/cm2 in 6 mol/L KOH aqueous solution, and a specific capacitance of 210 F/g has been maintained for 500 cycles. As the low cost of MnSO4 and KCr2O7 and the low reaction temperature, the present method avoids the requirements for complicated operations, time/energy-consuming and expensive reagents, and perhaps is ready for the industrialization of nano-MnO2 production.展开更多
基金Funded by National Natural Science Foundation of China(No.51301070)Scientific and Technological Project of Henan Province(No.182102210068)
文摘To improve both oxygen evolution efficiency and stability at high temperatures, Mn, Mn+Mo, Mn+Mo+V, and Mn+Fe+V oxide electrodes were prepared on a Ti substrate, with an intermediate layer of IrO_2, by an anodic deposition method. The crystal structure, surface morphology, pore size distribution, specific surface area, and voltammetric charge were then characterized for each electrode. The results demonstrated that for Mn-O electrodes, the preferential orientation of the(100) crystal plane and the mesopore structure played negative roles in the oxygen evolution reaction. On the basis of the electrocatalytic properties of MnO2-based electrodes in seawater, the outer surface voltammetric charge at a scan rate of 500 mV·s-1 was shown to effectively indicate whether oxygen evolution reactions were preferred over chlorine evolution reactions. The Mn-O electrode exhibited oxygen evolution efficiency of only 47.27%, whereas the Mn+Mo, Mn+Mo+V and Mn+Fe+V oxide electrodes displayed oxygen evolution efficiency of nearly 100%. This means that adding Mo, V, and Fe elements to the electrode can improve its crystal structure and morphology as well as further enhancing its oxygen evolution efficiency.
基金financially supported by the National Natural Science Foundation of China(Nos.21273162,21473122,21501135)the Science and Technology of Shanghai Municipality,China(No.14DZ2261100)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Large Equipment Test Foundation of Tongji University
文摘We demonstrate a simple and highly efficient strategy to synthesize MnO2/nitrogen-doped ultramicroporous carbon nanospheres（MnO2/N-UCNs） for supercapacitor application.MnO2/N-UCNs were fabricated via a template-free polymerization of resorcinol/formaldehyde on the surface of phloroglucinol/terephthalaldehyde colloids in the presence of hexamethylenetetramine,followed by carbonization and then a redox reaction between carbons and KMnO4.As-prepared MnO2/N-UCNs exhibits regular ultramicropores,high surface area,nitrogen heteroatom,and high content of MnO2.A typical MnO2/N-UCNs with 57 wt.%MnO2 doping content（denoted as MnO2（57%）/N-UCNs） makes the most use of the synergistic effect between carbons and metal oxides.MnO2（57%）/N-UCNs as a supercapacitor electrode exhibits excellent electrochemical performance such as a high specific capacitance（401 F/g at 1.0 A/g） and excellent charge/discharge stability（86.3%of the initial capacitance after 10,000 cycles at 2.0 A/g） in 1.0 mol/L Na2SO4 electrolyte.The well-designed and high-performance MnO2/N-UCNs highlight the great potential for advanced supercapacitor applications.
基金Projects(21071153,20976198)supported by the National Natural Science Foundation of China
文摘Nanostructured MnO2/CNT composite was synthesized by a soft template approach in the presence of Pluronic P123 surfactant. The product was characterized by X-ray diffraction, thermogravimetric and differential thermal analyses, Fourier transformed infrared spectroscopy and high-resolution transmission electron microscopy. The results show that the sample consists of poor crystalline α-MnO2 nanorods with a diameter of about 10 nm and a length of 30-50 nm, which absorb on the carbon nanotubes. The electrochemical properties of the product as cathode material for Li-MnO2 cell are evaluated by galvanostatic charge-discharge and electrochemical impedance spectroscopy （EIS）. Compared with pure MnO2 electrode, the MnO2/CNT composite delivers a much larger initial capacity of 275.3 mA-h/g and better rate and cycling performance.
基金supported by the National Natural Science Foundation of China (51203071,51363014 and 21163010)the Key Project of Chinese Ministry of Education (212183)+1 种基金the Program for Hongliu Young Teachers in Lanzhou University of Technology (201201)the Natural Science Funds for Distinguished Young Scholars of Gansu Province (1111RJDA012)
文摘A novel bird nest-like nanostructured MnO2(BNNS-MnO2) was prepared by a facile and cost-effective strategy. Their structures and morphologies were characterized by field emission scanning electron microscopy, transmission electron microscopy and powder X-ray diffraction. Capacitive behaviors were investigated by cyclic voltammetry and galvanostatic charge-discharge. The obtained nano-MnO2 possesses a well designed loose-assembled hierarchical nanoarchitecture with an appropriate crystallinity which gives rise to excellent performances as an electrode material for supercapacitors. A maximum specific capacitance of 917 F/g has been obtained at a current density of 5 mA/cm2 in 6 mol/L KOH aqueous solution, and a specific capacitance of 210 F/g has been maintained for 500 cycles. As the low cost of MnSO4 and KCr2O7 and the low reaction temperature, the present method avoids the requirements for complicated operations, time/energy-consuming and expensive reagents, and perhaps is ready for the industrialization of nano-MnO2 production.
